// Copyright 2009-2021 Intel Corporation
// SPDX-License-Identifier: Apache-2.0

#include "pathtracer_device.h"

#include "../common/lights/ambient_light.cpp"
#include "../common/lights/directional_light.cpp"
#include "../common/lights/point_light.cpp"
#include "../common/lights/quad_light.cpp"
#include "../common/lights/spot_light.cpp"

namespace embree {

#define USE_ARGUMENT_CALLBACKS 1

//RTC_SYCL_INDIRECTLY_CALLABLE void occlusionFilterOpaque(const RTCFilterFunctionNArguments* args);
RTC_SYCL_INDIRECTLY_CALLABLE void occlusionFilterHair(const RTCFilterFunctionNArguments* args);

#undef TILE_SIZE_X
#undef TILE_SIZE_Y

#define TILE_SIZE_X 4
#define TILE_SIZE_Y 4

#define FIXED_SAMPLING 0

#define FIXED_EDGE_TESSELLATION_VALUE 4

#define ENABLE_FILTER_FUNCTION 0

#define MAX_EDGE_LEVEL 128.0f
#define MIN_EDGE_LEVEL   4.0f
#define LEVEL_FACTOR    64.0f

TutorialData data;
extern "C" int g_animation_mode;

bool g_subdiv_mode = false;
unsigned int keyframeID = 0;

#if defined(EMBREE_SYCL_TUTORIAL) && !defined(EMBREE_SYCL_RT_SIMULATION) && defined(USE_SPECIALIZATION_CONSTANTS)
const static sycl::specialization_id<RTCFeatureFlags> rtc_feature_mask(RTC_FEATURE_FLAG_ALL);
#endif
RTCFeatureFlags g_used_features = RTC_FEATURE_FLAG_NONE;

////////////////////////////////////////////////////////////////////////////////
//                               Lights                                       //
////////////////////////////////////////////////////////////////////////////////

Light_SampleRes Lights_sample(const Light* self,
                              const DifferentialGeometry& dg, /*! point to generate the sample for >*/
                              const Vec2f s)                /*! random numbers to generate the sample >*/
{
  TutorialLightType ty = self->type;
  switch (ty) {
  case LIGHT_AMBIENT    : return AmbientLight_sample(self,dg,s);
  case LIGHT_POINT      : return PointLight_sample(self,dg,s);
  case LIGHT_DIRECTIONAL: return DirectionalLight_sample(self,dg,s);
  case LIGHT_SPOT       : return SpotLight_sample(self,dg,s);
  case LIGHT_QUAD       : return QuadLight_sample(self,dg,s);
  default: {
    Light_SampleRes res;
    res.weight = Vec3fa(0,0,0);
    res.dir = Vec3fa(0,0,0);
    res.dist = 0;
    res.pdf = inf;
    return res;
  }
  }
}
  
Light_EvalRes Lights_eval(const Light* self,
                          const DifferentialGeometry& dg,
                          const Vec3fa& dir)
{
  TutorialLightType ty = self->type;
  switch (ty) {
  case LIGHT_AMBIENT     : return AmbientLight_eval(self,dg,dir);
  case LIGHT_POINT       : return PointLight_eval(self,dg,dir);
  case LIGHT_DIRECTIONAL : return DirectionalLight_eval(self,dg,dir);
  case LIGHT_SPOT        : return SpotLight_eval(self,dg,dir);
  case LIGHT_QUAD        : return QuadLight_eval(self,dg,dir);
  default: {
    Light_EvalRes res;
    res.value = Vec3fa(0,0,0);
    res.dist = inf;
    res.pdf = 0.f;
    return res;
  }
  }
}

  
////////////////////////////////////////////////////////////////////////////////
//                                 BRDF                                       //
////////////////////////////////////////////////////////////////////////////////

struct BRDF
{
  float Ns;               /*< specular exponent */
  float Ni;               /*< optical density for the surface (index of refraction) */
  Vec3fa Ka;              /*< ambient reflectivity */
  Vec3fa Kd;              /*< diffuse reflectivity */
  Vec3fa Ks;              /*< specular reflectivity */
  Vec3fa Kt;              /*< transmission filter */
  float dummy[30];
};

struct Medium
{
  Vec3fa transmission; //!< Transmissivity of medium.
  float eta;             //!< Refraction index of medium.
};

inline Medium make_Medium(const Vec3fa& transmission, const float eta)
{
  Medium m;
  m.transmission = transmission;
  m.eta = eta;
  return m;
}

inline Medium make_Medium_Vacuum() {
  return make_Medium(Vec3fa((float)1.0f),1.0f);
}

inline bool eq(const Medium& a, const Medium& b) {
  return (a.eta == b.eta) && eq(a.transmission, b.transmission);
}

inline Vec3fa sample_component2(const Vec3fa& c0, const Sample3f& wi0, const Medium& medium0,
                               const Vec3fa& c1, const Sample3f& wi1, const Medium& medium1,
                               const Vec3fa& Lw, Sample3f& wi_o, Medium& medium_o, const float s)
{
  const Vec3fa m0 = Lw*c0/wi0.pdf;
  const Vec3fa m1 = Lw*c1/wi1.pdf;

  const float C0 = wi0.pdf == 0.0f ? 0.0f : max(max(m0.x,m0.y),m0.z);
  const float C1 = wi1.pdf == 0.0f ? 0.0f : max(max(m1.x,m1.y),m1.z);
  const float C  = C0 + C1;

  if (C == 0.0f) {
    wi_o = make_Sample3f(Vec3fa(0,0,0),0);
    return Vec3fa(0,0,0);
  }

  const float CP0 = C0/C;
  const float CP1 = C1/C;
  if (s < CP0) {
    wi_o = make_Sample3f(wi0.v,wi0.pdf*CP0);
    medium_o = medium0; return c0;
  }
  else {
    wi_o = make_Sample3f(wi1.v,wi1.pdf*CP1);
    medium_o = medium1; return c1;
  }
}

////////////////////////////////////////////////////////////////////////////////
//                          Minneart BRDF                                     //
////////////////////////////////////////////////////////////////////////////////

struct Minneart
{
  /*! The reflectance parameter. The vale 0 means no reflection,
   *  and 1 means full reflection. */
  Vec3fa R;

  /*! The amount of backscattering. A value of 0 means lambertian
   *  diffuse, and inf means maximum backscattering. */
  float b;
};

inline Vec3fa Minneart__eval(const Minneart* This,
                     const Vec3fa &wo, const DifferentialGeometry &dg, const Vec3fa &wi)
{
  const float cosThetaI = clamp(dot(wi,dg.Ns));
  const float backScatter = powf(clamp(dot(wo,wi)), This->b);
  return (backScatter * cosThetaI * float(one_over_pi)) * This->R;
}

inline Vec3fa Minneart__sample(const Minneart* This,
                       const Vec3fa &wo,
                       const DifferentialGeometry &dg,
                       Sample3f &wi,
                       const Vec2f &s)
{
  wi = cosineSampleHemisphere(s.x,s.y,dg.Ns);
  return Minneart__eval(This, wo, dg, wi.v);
}

inline void Minneart__Constructor(Minneart* This, const Vec3fa& R, const float b)
{
  This->R = R;
  This->b = b;
}

inline Minneart make_Minneart(const Vec3fa& R, const float f) {
  Minneart m; Minneart__Constructor(&m,R,f); return m;
}

////////////////////////////////////////////////////////////////////////////////
//                            Velvet BRDF                                     //
////////////////////////////////////////////////////////////////////////////////

struct Velvety
{
  BRDF base;

  /*! The reflectance parameter. The vale 0 means no reflection,
   *  and 1 means full reflection. */
  Vec3fa R;

  /*! The falloff of horizon scattering. 0 no falloff,
   *  and inf means maximum falloff. */
  float f;
};

inline Vec3fa Velvety__eval(const Velvety* This,
                    const Vec3fa &wo, const DifferentialGeometry &dg, const Vec3fa &wi)
{
  const float cosThetaO = clamp(dot(wo,dg.Ns));
  const float cosThetaI = clamp(dot(wi,dg.Ns));
  const float sinThetaO = sqrt(1.0f - cosThetaO * cosThetaO);
  const float horizonScatter = powf(sinThetaO, This->f);
  return (horizonScatter * cosThetaI * float(one_over_pi)) * This->R;
}

inline Vec3fa Velvety__sample(const Velvety* This,
                      const Vec3fa &wo,
                      const DifferentialGeometry &dg,
                      Sample3f &wi,
                      const Vec2f &s)
{
  wi = cosineSampleHemisphere(s.x,s.y,dg.Ns);
  return Velvety__eval(This, wo, dg, wi.v);
}

inline void Velvety__Constructor(Velvety* This, const Vec3fa& R, const float f)
{
  This->R = R;
  This->f = f;
}

inline Velvety make_Velvety(const Vec3fa& R, const float f) {
  Velvety m; Velvety__Constructor(&m,R,f); return m;
}

////////////////////////////////////////////////////////////////////////////////
//                  Dielectric Reflection BRDF                                //
////////////////////////////////////////////////////////////////////////////////

struct DielectricReflection
{
  float eta;
};

inline Vec3fa DielectricReflection__eval(const DielectricReflection* This, const Vec3fa &wo, const DifferentialGeometry &dg, const Vec3fa &wi) {
  return Vec3fa(0.f);
}

inline Vec3fa DielectricReflection__sample(const DielectricReflection* This, const Vec3fa &wo, const DifferentialGeometry &dg, Sample3f &wi, const Vec2f &s)
{
  const float cosThetaO = clamp(dot(wo,dg.Ns));
  wi = make_Sample3f(reflect(wo,dg.Ns,cosThetaO),1.0f);
  return Vec3fa(fresnelDielectric(cosThetaO,This->eta));
}

inline void DielectricReflection__Constructor(DielectricReflection* This,
                                              const float etai,
                                              const float etat)
{
  This->eta = etai*rcp(etat);
}

inline DielectricReflection make_DielectricReflection(const float etai, const float etat) {
  DielectricReflection v; DielectricReflection__Constructor(&v,etai,etat); return v;
}

////////////////////////////////////////////////////////////////////////////////
//                                Lambertian BRDF                             //
////////////////////////////////////////////////////////////////////////////////

struct Lambertian
{
  Vec3fa R;
};

inline Vec3fa Lambertian__eval(const Lambertian* This,
                              const Vec3fa &wo, const DifferentialGeometry &dg, const Vec3fa &wi)
{
  return This->R * (1.0f/(float)(float(M_PI))) * clamp(dot(wi,dg.Ns));
}

inline Vec3fa Lambertian__sample(const Lambertian* This,
                                const Vec3fa &wo,
                                const DifferentialGeometry &dg,
                                Sample3f &wi,
                                const Vec2f &s)
{
  wi = cosineSampleHemisphere(s.x,s.y,dg.Ns);
  return Lambertian__eval(This, wo, dg, wi.v);
}

inline void Lambertian__Constructor(Lambertian* This, const Vec3fa& R)
{
  This->R = R;
}

inline Lambertian make_Lambertian(const Vec3fa& R) {
  Lambertian v; Lambertian__Constructor(&v,R); return v;
}


////////////////////////////////////////////////////////////////////////////////
//              Lambertian BRDF with Dielectric Layer on top                  //
////////////////////////////////////////////////////////////////////////////////

struct DielectricLayerLambertian
{
  Vec3fa T;             //!< Transmission coefficient of dielectricum
  float etait;         //!< Relative refraction index etai/etat of both media
  float etati;         //!< relative refraction index etat/etai of both media
  Lambertian ground;   //!< the BRDF of the ground layer
};

inline Vec3fa DielectricLayerLambertian__eval(const DielectricLayerLambertian* This,
                                             const Vec3fa &wo, const DifferentialGeometry &dg, const Vec3fa &wi)
{
  const float cosThetaO = dot(wo,dg.Ns);
  const float cosThetaI = dot(wi,dg.Ns);
  if (cosThetaI <= 0.0f || cosThetaO <= 0.0f) return Vec3fa(0.f);

  float cosThetaO1;
  const Sample3f wo1 = refract(wo,dg.Ns,This->etait,cosThetaO,cosThetaO1);
  float cosThetaI1;
  const Sample3f wi1 = refract(wi,dg.Ns,This->etait,cosThetaI,cosThetaI1);
  const float Fi = 1.0f - fresnelDielectric(cosThetaI,cosThetaI1,This->etait);
  const Vec3fa Fg = Lambertian__eval(&This->ground,neg(wo1.v),dg,neg(wi1.v));
  const float Fo = 1.0f - fresnelDielectric(cosThetaO,cosThetaO1,This->etait);
  return Fo * This->T * Fg * This->T * Fi;
}

inline Vec3fa DielectricLayerLambertian__sample(const DielectricLayerLambertian* This,
                                               const Vec3fa &wo,
                                               const DifferentialGeometry &dg,
                                               Sample3f &wi,
                                               const Vec2f &s)
{
  /*! refract ray into medium */
  float cosThetaO = dot(wo,dg.Ns);
  if (cosThetaO <= 0.0f) { wi = make_Sample3f(Vec3fa(0.0f),0.0f); return Vec3fa(0.f); }
  float cosThetaO1; Sample3f wo1 = refract(wo,dg.Ns,This->etait,cosThetaO,cosThetaO1);

  /*! sample ground BRDF */
  Sample3f wi1 = make_Sample3f(Vec3fa(0.f),1.f);
  Vec3fa Fg = Lambertian__sample(&This->ground,neg(wo1.v),dg,wi1,s);

  /*! refract ray out of medium */
  float cosThetaI1 = dot(wi1.v,dg.Ns);
  if (cosThetaI1 <= 0.0f) { wi = make_Sample3f(Vec3fa(0.0f),0.0f); return Vec3fa(0.f); }

  float cosThetaI;
  Sample3f wi0 = refract(neg(wi1.v),neg(dg.Ns),This->etati,cosThetaI1,cosThetaI);
  if (wi0.pdf == 0.0f) { wi = make_Sample3f(Vec3fa(0.0f),0.0f); return Vec3fa(0.f); }

  /*! accumulate contribution of path */
  wi = make_Sample3f(wi0.v,wi1.pdf);
  float Fi = 1.0f - fresnelDielectric(cosThetaI,cosThetaI1,This->etait);
  float Fo = 1.0f - fresnelDielectric(cosThetaO,cosThetaO1,This->etait);
  return Fo * This->T * Fg * This->T * Fi;
}

inline void DielectricLayerLambertian__Constructor(DielectricLayerLambertian* This,
                                                   const Vec3fa& T,
                                                   const float etai,
                                                   const float etat,
                                                   const Lambertian& ground)
{
  This->T = T;
  This->etait = etai*rcp(etat);
  This->etati = etat*rcp(etai);
  This->ground = ground;
}

inline DielectricLayerLambertian make_DielectricLayerLambertian(const Vec3fa& T,
                                                                        const float etai,
                                                                        const float etat,
                                                                        const Lambertian& ground)
{
  DielectricLayerLambertian m;
  DielectricLayerLambertian__Constructor(&m,T,etai,etat,ground);
  return m;
}

/*! Anisotropic power cosine microfacet distribution. */
struct AnisotropicBlinn {
  Vec3fa dx;       //!< x-direction of the distribution.
  Vec3fa dy;       //!< y-direction of the distribution.
  Vec3fa dz;       //!< z-direction of the distribution.
  Vec3fa Kr,Kt;
  float nx;        //!< Glossiness in x direction with range [0,infinity[ where 0 is a diffuse surface.
  float ny;        //!< Exponent that determines the glossiness in y direction.
  float norm1;     //!< Normalization constant for calculating the pdf for sampling.
  float norm2;     //!< Normalization constant for calculating the distribution.
  float side;
};

  /*! Anisotropic power cosine distribution constructor. */
inline void AnisotropicBlinn__Constructor(AnisotropicBlinn* This, const Vec3fa& Kr, const Vec3fa& Kt,
                                          const Vec3fa& dx, float nx, const Vec3fa& dy, float ny, const Vec3fa& dz)
{
  This->Kr = Kr;
  This->Kt = Kt;
  This->dx = dx;
  This->nx = nx;
  This->dy = dy;
  This->ny = ny;
  This->dz = dz;
  This->norm1 = sqrtf((nx+1)*(ny+1)) * float(one_over_two_pi);
  This->norm2 = sqrtf((nx+2)*(ny+2)) * float(one_over_two_pi);
  This->side = reduce_max(Kr)/(reduce_max(Kr)+reduce_max(Kt));
}

/*! Evaluates the power cosine distribution. \param wh is the half
 *  vector */
inline float AnisotropicBlinn__eval(const AnisotropicBlinn* This, const Vec3fa& wh)
{
  const float cosPhiH   = dot(wh, This->dx);
  const float sinPhiH   = dot(wh, This->dy);
  const float cosThetaH = dot(wh, This->dz);
  const float R = sqr(cosPhiH)+sqr(sinPhiH);
  if (R == 0.0f) return This->norm2;
  const float n = (This->nx*sqr(cosPhiH)+This->ny*sqr(sinPhiH))*rcp(R);
  return This->norm2 * powf(abs(cosThetaH), n);
}

/*! Samples the distribution. \param s is the sample location
 *  provided by the caller. */
inline Vec3ff AnisotropicBlinn__sample(const AnisotropicBlinn* This, const float sx, const float sy)
{
  const float phi =float(two_pi)*sx;
  const float sinPhi0 = sqrtf(This->nx+1)*sinf(phi);
  const float cosPhi0 = sqrtf(This->ny+1)*cosf(phi);
  const float norm = rsqrt(sqr(sinPhi0)+sqr(cosPhi0));
  const float sinPhi = sinPhi0*norm;
  const float cosPhi = cosPhi0*norm;
  const float n = This->nx*sqr(cosPhi)+This->ny*sqr(sinPhi);
  const float cosTheta = powf(sy,rcp(n+1));
  const float sinTheta = cos2sin(cosTheta);
  const float pdf = This->norm1*powf(cosTheta,n);
  const Vec3fa h = Vec3fa(cosPhi * sinTheta, sinPhi * sinTheta, cosTheta);
  const Vec3fa wh = h.x*This->dx + h.y*This->dy + h.z*This->dz;
  return Vec3ff(wh,pdf);
}

inline Vec3fa AnisotropicBlinn__eval(const AnisotropicBlinn* This, const Vec3fa& wo, const Vec3fa& wi)
{
  const float cosThetaI = dot(wi,This->dz);

  /* reflection */
  if (cosThetaI > 0.0f) {
    const Vec3fa wh = normalize(wi + wo);
    return This->Kr * AnisotropicBlinn__eval(This,wh) * abs(cosThetaI);
  }

  /* transmission */
  else {
    const Vec3fa wh = normalize(reflect(wi,This->dz) + wo);
    return This->Kt * AnisotropicBlinn__eval(This,wh) * abs(cosThetaI);
  }
}

inline Vec3fa AnisotropicBlinn__sample(const AnisotropicBlinn* This, const Vec3fa& wo, Sample3f& wi_o, const float sx, const float sy, const float sz)
{
  //wi = Vec3fa(reflect(normalize(wo),normalize(dz)),1.0f); return Kr;
  //wi = Vec3fa(neg(wo),1.0f); return Kt;
  const Vec3ff wh = AnisotropicBlinn__sample(This,sx,sy);
  //if (dot(wo,wh) < 0.0f) return Vec3fa(0.0f,0.0f);

  /* reflection */
  if (sz < This->side) {
    wi_o = make_Sample3f(reflect(wo,Vec3fa(wh)),wh.w*This->side);
    const float cosThetaI = dot(wi_o.v,This->dz);
    return This->Kr * AnisotropicBlinn__eval(This,Vec3fa(wh)) * abs(cosThetaI);
  }

  /* transmission */
  else {
    wi_o = make_Sample3f(reflect(reflect(wo,Vec3fa(wh)),This->dz),wh.w*(1-This->side));
    const float cosThetaI = dot(wi_o.v,This->dz);
    return This->Kt * AnisotropicBlinn__eval(This,Vec3fa(wh)) * abs(cosThetaI);
  }
}

////////////////////////////////////////////////////////////////////////////////
//                          Matte Material                                    //
////////////////////////////////////////////////////////////////////////////////

void MatteMaterial__preprocess(ISPCMatteMaterial* material, BRDF& brdf, const Vec3fa& wo, const DifferentialGeometry& dg, const Medium& medium)
{
}

Vec3fa MatteMaterial__eval(ISPCMatteMaterial* This, const BRDF& brdf, const Vec3fa& wo, const DifferentialGeometry& dg, const Vec3fa& wi)
{
  Lambertian lambertian = make_Lambertian(Vec3fa((Vec3fa)This->reflectance));
  return Lambertian__eval(&lambertian,wo,dg,wi);
}

Vec3fa MatteMaterial__sample(ISPCMatteMaterial* This, const BRDF& brdf, const Vec3fa& Lw, const Vec3fa& wo, const DifferentialGeometry& dg, Sample3f& wi_o, Medium& medium, const Vec2f& s)
{
  Lambertian lambertian = make_Lambertian(Vec3fa((Vec3fa)This->reflectance));
  return Lambertian__sample(&lambertian,wo,dg,wi_o,s);
}

////////////////////////////////////////////////////////////////////////////////
//                          Mirror Material                                    //
////////////////////////////////////////////////////////////////////////////////

void MirrorMaterial__preprocess(ISPCMirrorMaterial* material, BRDF& brdf, const Vec3fa& wo, const DifferentialGeometry& dg, const Medium& medium)
{
}

Vec3fa MirrorMaterial__eval(ISPCMirrorMaterial* This, const BRDF& brdf, const Vec3fa& wo, const DifferentialGeometry& dg, const Vec3fa& wi) {
  return Vec3fa(0.0f);
}

Vec3fa MirrorMaterial__sample(ISPCMirrorMaterial* This, const BRDF& brdf, const Vec3fa& Lw, const Vec3fa& wo, const DifferentialGeometry& dg, Sample3f& wi_o, Medium& medium, const Vec2f& s)
{
  wi_o = make_Sample3f(reflect(wo,dg.Ns),1.0f);
  return Vec3fa(This->reflectance);
}

////////////////////////////////////////////////////////////////////////////////
//                          OBJ Material                                      //
////////////////////////////////////////////////////////////////////////////////

void OBJMaterial__preprocess(ISPCOBJMaterial* material, BRDF& brdf, const Vec3fa& wo, const DifferentialGeometry& dg, const Medium& medium)
{
    float d = material->d;
    if (material->map_d) d *= getTextureTexel1f(material->map_d,dg.u,dg.v);
    brdf.Ka = Vec3fa(material->Ka);
    //if (material->map_Ka) { brdf.Ka *= material->map_Ka->get(dg.st); }
    brdf.Kd = d * Vec3fa(material->Kd);
    if (material->map_Kd) brdf.Kd = brdf.Kd * getTextureTexel3f(material->map_Kd,dg.u,dg.v);
    brdf.Ks = d * Vec3fa(material->Ks);
    //if (material->map_Ks) brdf.Ks *= material->map_Ks->get(dg.st);
    brdf.Ns = material->Ns;
    //if (material->map_Ns) { brdf.Ns *= material->map_Ns.get(dg.st); }
    brdf.Kt = (1.0f-d)*Vec3fa(material->Kt);
    brdf.Ni = material->Ni;
}

Vec3fa OBJMaterial__eval(ISPCOBJMaterial* material, const BRDF& brdf, const Vec3fa& wo, const DifferentialGeometry& dg, const Vec3fa& wi)
{
  Vec3fa R = Vec3fa(0.0f);
  const float Md = max(max(brdf.Kd.x,brdf.Kd.y),brdf.Kd.z);
  const float Ms = max(max(brdf.Ks.x,brdf.Ks.y),brdf.Ks.z);
  const float Mt = max(max(brdf.Kt.x,brdf.Kt.y),brdf.Kt.z);
  if (Md > 0.0f) {
    R = R + (1.0f/float(M_PI)) * clamp(dot(wi,dg.Ns)) * brdf.Kd;
  }
  if (Ms > 0.0f) {
    const Sample3f refl = make_Sample3f(reflect(wo,dg.Ns),1.0f);
    if (dot(refl.v,wi) > 0.0f)
      R = R + (brdf.Ns+2) * float(one_over_two_pi) * powf(max(1e-10f,dot(refl.v,wi)),brdf.Ns) * clamp(dot(wi,dg.Ns)) * brdf.Ks;
  }
  if (Mt > 0.0f) {
  }
  return R;
}

Vec3fa OBJMaterial__sample(ISPCOBJMaterial* material, const BRDF& brdf, const Vec3fa& Lw, const Vec3fa& wo, const DifferentialGeometry& dg, Sample3f& wi_o, Medium& medium, const Vec2f& s)
{
  Vec3fa cd = Vec3fa(0.0f);
  Sample3f wid = make_Sample3f(Vec3fa(0.0f),0.0f);
  if (max(max(brdf.Kd.x,brdf.Kd.y),brdf.Kd.z) > 0.0f) {
    wid = cosineSampleHemisphere(s.x,s.y,dg.Ns);
    cd = float(one_over_pi) * clamp(dot(wid.v,dg.Ns)) * brdf.Kd;
  }

  Vec3fa cs = Vec3fa(0.0f);
  Sample3f wis = make_Sample3f(Vec3fa(0.0f),0.0f);
  if (max(max(brdf.Ks.x,brdf.Ks.y),brdf.Ks.z) > 0.0f)
  {
    const Sample3f refl = make_Sample3f(reflect(wo,dg.Ns),1.0f);
    wis.v = powerCosineSampleHemisphere(brdf.Ns,s);
    wis.pdf = powerCosineSampleHemispherePDF(wis.v,brdf.Ns);
    wis.v = frame(refl.v) * wis.v;
    cs = (brdf.Ns+2) * float(one_over_two_pi) * powf(max(dot(refl.v,wis.v),1e-10f),brdf.Ns) * clamp(dot(wis.v,dg.Ns)) * brdf.Ks;
  }

  Vec3fa ct = Vec3fa(0.0f);
  Sample3f wit = make_Sample3f(Vec3fa(0.0f),0.0f);
  if (max(max(brdf.Kt.x,brdf.Kt.y),brdf.Kt.z) > 0.0f)
  {
    wit = make_Sample3f(neg(wo),1.0f);
    ct = brdf.Kt;
  }

  const Vec3fa md = Lw*cd/wid.pdf;
  const Vec3fa ms = Lw*cs/wis.pdf;
  const Vec3fa mt = Lw*ct/wit.pdf;

  const float Cd = wid.pdf == 0.0f ? 0.0f : max(max(md.x,md.y),md.z);
  const float Cs = wis.pdf == 0.0f ? 0.0f : max(max(ms.x,ms.y),ms.z);
  const float Ct = wit.pdf == 0.0f ? 0.0f : max(max(mt.x,mt.y),mt.z);
  const float C  = Cd + Cs + Ct;

  if (C == 0.0f) {
    wi_o = make_Sample3f(Vec3fa(0,0,0),0);
    return Vec3fa(0,0,0);
  }

  const float CPd = Cd/C;
  const float CPs = Cs/C;
  const float CPt = Ct/C;

  if (s.x < CPd) {
    wi_o = make_Sample3f(wid.v,wid.pdf*CPd);
    return cd;
  }
  else if (s.x < CPd + CPs)
  {
    wi_o = make_Sample3f(wis.v,wis.pdf*CPs);
    return cs;
  }
  else
  {
    wi_o = make_Sample3f(wit.v,wit.pdf*CPt);
    return ct;
  }
}

////////////////////////////////////////////////////////////////////////////////
//                        Metal Material                                      //
////////////////////////////////////////////////////////////////////////////////

void MetalMaterial__preprocess(ISPCMetalMaterial* material, BRDF& brdf, const Vec3fa& wo, const DifferentialGeometry& dg, const Medium& medium)
{
}

Vec3fa MetalMaterial__eval(ISPCMetalMaterial* This, const BRDF& brdf, const Vec3fa& wo, const DifferentialGeometry& dg, const Vec3fa& wi)
{
  const FresnelConductor fresnel = make_FresnelConductor(Vec3fa(This->eta),Vec3fa(This->k));
  const PowerCosineDistribution distribution = make_PowerCosineDistribution(rcp(This->roughness));

  const float cosThetaO = dot(wo,dg.Ns);
  const float cosThetaI = dot(wi,dg.Ns);
  if (cosThetaI <= 0.0f || cosThetaO <= 0.0f) return Vec3fa(0.f);
  const Vec3fa wh = normalize(wi+wo);
  const float cosThetaH = dot(wh, dg.Ns);
  const float cosTheta = dot(wi, wh); // = dot(wo, wh);
  const Vec3fa F = eval(fresnel,cosTheta);
  const float D = eval(distribution,cosThetaH);
  const float G = min(1.0f, min(2.0f * cosThetaH * cosThetaO / cosTheta,
                                2.0f * cosThetaH * cosThetaI / cosTheta));
  return (Vec3fa(This->reflectance)*F) * D * G * rcp(4.0f*cosThetaO);
}

Vec3fa MetalMaterial__sample(ISPCMetalMaterial* This, const BRDF& brdf, const Vec3fa& Lw, const Vec3fa& wo, const DifferentialGeometry& dg, Sample3f& wi_o, Medium& medium, const Vec2f& s)
{
  const PowerCosineDistribution distribution = make_PowerCosineDistribution(rcp(This->roughness));

  if (dot(wo,dg.Ns) <= 0.0f) { wi_o = make_Sample3f(Vec3fa(0.0f),0.0f); return Vec3fa(0.f); }
  sample(distribution,wo,dg.Ns,wi_o,s);
  if (dot(wi_o.v,dg.Ns) <= 0.0f) { wi_o = make_Sample3f(Vec3fa(0.0f),0.0f); return Vec3fa(0.f); }
  return MetalMaterial__eval(This,brdf,wo,dg,wi_o.v);
}

////////////////////////////////////////////////////////////////////////////////
//                        ReflectiveMetal Material                            //
////////////////////////////////////////////////////////////////////////////////

void ReflectiveMetalMaterial__preprocess(ISPCReflectiveMetalMaterial* material, BRDF& brdf, const Vec3fa& wo, const DifferentialGeometry& dg, const Medium& medium)  {
}

Vec3fa ReflectiveMetalMaterial__eval(ISPCReflectiveMetalMaterial* This, const BRDF& brdf, const Vec3fa& wo, const DifferentialGeometry& dg, const Vec3fa& wi) {
  return Vec3fa(0.0f);
}

Vec3fa ReflectiveMetalMaterial__sample(ISPCReflectiveMetalMaterial* This, const BRDF& brdf, const Vec3fa& Lw, const Vec3fa& wo, const DifferentialGeometry& dg, Sample3f& wi_o, Medium& medium, const Vec2f& s)
{
  wi_o = make_Sample3f(reflect(wo,dg.Ns),1.0f);
  return Vec3fa(This->reflectance) * fresnelConductor(dot(wo,dg.Ns),Vec3fa((Vec3fa)This->eta),Vec3fa((Vec3fa)This->k));
}

////////////////////////////////////////////////////////////////////////////////
//                        Velvet Material                                     //
////////////////////////////////////////////////////////////////////////////////

void VelvetMaterial__preprocess(ISPCVelvetMaterial* material, BRDF& brdf, const Vec3fa& wo, const DifferentialGeometry& dg, const Medium& medium)
{
}

Vec3fa VelvetMaterial__eval(ISPCVelvetMaterial* This, const BRDF& brdf, const Vec3fa& wo, const DifferentialGeometry& dg, const Vec3fa& wi)
{
  Minneart minneart; Minneart__Constructor(&minneart,(Vec3fa)Vec3fa(This->reflectance),This->backScattering);
  Velvety velvety; Velvety__Constructor (&velvety,Vec3fa((Vec3fa)This->horizonScatteringColor),This->horizonScatteringFallOff);
  return Minneart__eval(&minneart,wo,dg,wi) + Velvety__eval(&velvety,wo,dg,wi);
}

Vec3fa VelvetMaterial__sample(ISPCVelvetMaterial* This, const BRDF& brdf, const Vec3fa& Lw, const Vec3fa& wo, const DifferentialGeometry& dg, Sample3f& wi_o, Medium& medium, const Vec2f& s)
{
  Minneart minneart; Minneart__Constructor(&minneart,Vec3fa((Vec3fa)This->reflectance),This->backScattering);
  Velvety velvety; Velvety__Constructor (&velvety,Vec3fa((Vec3fa)This->horizonScatteringColor),This->horizonScatteringFallOff);

  Sample3f wi0; Vec3fa c0 = Minneart__sample(&minneart,wo,dg,wi0,s);
  Sample3f wi1; Vec3fa c1 = Velvety__sample(&velvety,wo,dg,wi1,s);
  return sample_component2(c0,wi0,medium,c1,wi1,medium,Lw,wi_o,medium,s.x);
}

////////////////////////////////////////////////////////////////////////////////
//                          Dielectric Material                               //
////////////////////////////////////////////////////////////////////////////////

void DielectricMaterial__preprocess(ISPCDielectricMaterial* material, BRDF& brdf, const Vec3fa& wo, const DifferentialGeometry& dg, const Medium& medium)
{
}

Vec3fa DielectricMaterial__eval(ISPCDielectricMaterial* material, const BRDF& brdf, const Vec3fa& wo, const DifferentialGeometry& dg, const Vec3fa& wi) {
  return Vec3fa(0.0f);
}

Vec3fa DielectricMaterial__sample(ISPCDielectricMaterial* material, const BRDF& brdf, const Vec3fa& Lw, const Vec3fa& wo, const DifferentialGeometry& dg, Sample3f& wi_o, Medium& medium, const Vec2f& s)
{
  float eta = 0.0f;
  Medium mediumOutside = make_Medium(Vec3fa((Vec3fa)material->transmissionOutside),material->etaOutside);
  Medium mediumInside  = make_Medium(Vec3fa((Vec3fa)material->transmissionInside ),material->etaInside );
  Medium mediumFront, mediumBack;
  if (eq(medium,mediumInside)) {
    eta = material->etaInside/material->etaOutside;
    mediumFront = mediumInside;
    mediumBack = mediumOutside;
  }
  else {
    eta = material->etaOutside/material->etaInside;
    mediumFront = mediumOutside;
    mediumBack = mediumInside;
  }

  float cosThetaO = clamp(dot(wo,dg.Ns));
  float cosThetaI; Sample3f wit = refract(wo,dg.Ns,eta,cosThetaO,cosThetaI);
  Sample3f wis = make_Sample3f(reflect(wo,dg.Ns),1.0f);
  float R = fresnelDielectric(cosThetaO,cosThetaI,eta);
  Vec3fa cs = Vec3fa(R);
  Vec3fa ct = Vec3fa(1.0f-R);
  return sample_component2(cs,wis,mediumFront,ct,wit,mediumBack,Lw,wi_o,medium,s.x);
}

////////////////////////////////////////////////////////////////////////////////
//                          ThinDielectric Material                               //
////////////////////////////////////////////////////////////////////////////////

void ThinDielectricMaterial__preprocess(ISPCThinDielectricMaterial* This, BRDF& brdf, const Vec3fa& wo, const DifferentialGeometry& dg, const Medium& medium)
{
}

Vec3fa ThinDielectricMaterial__eval(ISPCThinDielectricMaterial* This, const BRDF& brdf, const Vec3fa& wo, const DifferentialGeometry& dg, const Vec3fa& wi) {
  return Vec3fa(0.0f);
}

Vec3fa ThinDielectricMaterial__sample(ISPCThinDielectricMaterial* This, const BRDF& brdf, const Vec3fa& Lw, const Vec3fa& wo, const DifferentialGeometry& dg, Sample3f& wi_o, Medium& medium, const Vec2f& s)
{
  float cosThetaO = clamp(dot(wo,dg.Ns));
  if (cosThetaO <= 0.0f) return Vec3fa(0.0f);
  float R = fresnelDielectric(cosThetaO,rcp(This->eta));
  Sample3f wit = make_Sample3f(neg(wo),1.0f);
  Sample3f wis = make_Sample3f(reflect(wo,dg.Ns),1.0f);
  Vec3fa ct = exp(Vec3fa(This->transmissionFactor)*rcp(cosThetaO))*Vec3fa(1.0f-R);
  Vec3fa cs = Vec3fa(R);
  return sample_component2(cs,wis,medium,ct,wit,medium,Lw,wi_o,medium,s.x);
}

////////////////////////////////////////////////////////////////////////////////
//                     MetallicPaint Material                                 //
////////////////////////////////////////////////////////////////////////////////

void MetallicPaintMaterial__preprocess(ISPCMetallicPaintMaterial* material, BRDF& brdf, const Vec3fa& wo, const DifferentialGeometry& dg, const Medium& medium)
{
}

Vec3fa MetallicPaintMaterial__eval(ISPCMetallicPaintMaterial* This, const BRDF& brdf, const Vec3fa& wo, const DifferentialGeometry& dg, const Vec3fa& wi)
{
  DielectricReflection reflection; DielectricReflection__Constructor(&reflection, 1.0f, This->eta);
  DielectricLayerLambertian lambertian; DielectricLayerLambertian__Constructor(&lambertian, Vec3fa((float)1.0f), 1.0f, This->eta, make_Lambertian(Vec3fa((Vec3fa)This->shadeColor)));
  return DielectricReflection__eval(&reflection,wo,dg,wi) + DielectricLayerLambertian__eval(&lambertian,wo,dg,wi);
}

Vec3fa MetallicPaintMaterial__sample(ISPCMetallicPaintMaterial* This, const BRDF& brdf, const Vec3fa& Lw, const Vec3fa& wo, const DifferentialGeometry& dg, Sample3f& wi_o, Medium& medium, const Vec2f& s)
{
  DielectricReflection reflection; DielectricReflection__Constructor(&reflection, 1.0f, This->eta);
  DielectricLayerLambertian lambertian; DielectricLayerLambertian__Constructor(&lambertian, Vec3fa((float)1.0f), 1.0f, This->eta, make_Lambertian(Vec3fa((Vec3fa)This->shadeColor)));
  Sample3f wi0; Vec3fa c0 = DielectricReflection__sample(&reflection,wo,dg,wi0,s);
  Sample3f wi1; Vec3fa c1 = DielectricLayerLambertian__sample(&lambertian,wo,dg,wi1,s);
  return sample_component2(c0,wi0,medium,c1,wi1,medium,Lw,wi_o,medium,s.x);
}

////////////////////////////////////////////////////////////////////////////////
//                              Hair Material                                 //
////////////////////////////////////////////////////////////////////////////////

void HairMaterial__preprocess(ISPCHairMaterial* This, BRDF& brdf, const Vec3fa& wo, const DifferentialGeometry& dg, const Medium& medium)
{
  AnisotropicBlinn__Constructor((AnisotropicBlinn*)&brdf,Vec3fa(This->Kr),Vec3fa(This->Kt),dg.Tx,(float)This->nx,dg.Ty,(float)This->ny,dg.Ng);
}

Vec3fa HairMaterial__eval(ISPCHairMaterial* This, const BRDF& brdf, const Vec3fa& wo, const DifferentialGeometry& dg, const Vec3fa& wi)
{
  return AnisotropicBlinn__eval((AnisotropicBlinn*)&brdf,wo,wi);
}

Vec3fa HairMaterial__sample(ISPCHairMaterial* This, const BRDF& brdf, const Vec3fa& Lw, const Vec3fa& wo, const DifferentialGeometry& dg, Sample3f& wi_o, Medium& medium, const Vec2f& s)
{
  return AnisotropicBlinn__sample((AnisotropicBlinn*)&brdf,wo,wi_o,s.x,s.y,s.x);
}

////////////////////////////////////////////////////////////////////////////////
//                              Material                                      //
////////////////////////////////////////////////////////////////////////////////

inline void Material__preprocess(ISPCMaterial** materials, unsigned int materialID, unsigned int numMaterials, BRDF& brdf, const Vec3fa& wo, const DifferentialGeometry& dg, const Medium& medium)
{
  auto id = materialID;
  {
    if (id < numMaterials) // FIXME: workaround for ISPC bug, location reached with empty execution mask
    {
      ISPCMaterial* material = materials[id];

      switch (material->type) {
      case MATERIAL_OBJ  : OBJMaterial__preprocess  ((ISPCOBJMaterial*)  material,brdf,wo,dg,medium); break;
      case MATERIAL_METAL: MetalMaterial__preprocess((ISPCMetalMaterial*)material,brdf,wo,dg,medium); break;
      case MATERIAL_REFLECTIVE_METAL: ReflectiveMetalMaterial__preprocess((ISPCReflectiveMetalMaterial*)material,brdf,wo,dg,medium); break;
      case MATERIAL_VELVET: VelvetMaterial__preprocess((ISPCVelvetMaterial*)material,brdf,wo,dg,medium); break;
      case MATERIAL_DIELECTRIC: DielectricMaterial__preprocess((ISPCDielectricMaterial*)material,brdf,wo,dg,medium); break;
      case MATERIAL_METALLIC_PAINT: MetallicPaintMaterial__preprocess((ISPCMetallicPaintMaterial*)material,brdf,wo,dg,medium); break;
      case MATERIAL_MATTE: MatteMaterial__preprocess((ISPCMatteMaterial*)material,brdf,wo,dg,medium); break;
      case MATERIAL_MIRROR: MirrorMaterial__preprocess((ISPCMirrorMaterial*)material,brdf,wo,dg,medium); break;
      case MATERIAL_THIN_DIELECTRIC: ThinDielectricMaterial__preprocess((ISPCThinDielectricMaterial*)material,brdf,wo,dg,medium); break;
      case MATERIAL_HAIR: HairMaterial__preprocess((ISPCHairMaterial*)material,brdf,wo,dg,medium); break;
      default: break;
      }
    }
  }
}

inline Vec3fa Material__eval(ISPCMaterial** materials, unsigned int materialID, unsigned int numMaterials, const BRDF& brdf, const Vec3fa& wo, const DifferentialGeometry& dg, const Vec3fa& wi)
{
  Vec3fa c = Vec3fa(0.0f);
  auto id = materialID;
  {
    if (id < numMaterials) // FIXME: workaround for ISPC bug, location reached with empty execution mask
    {
      ISPCMaterial* material = materials[id];
      switch (material->type) {
      case MATERIAL_OBJ  : c = OBJMaterial__eval  ((ISPCOBJMaterial*)  material, brdf, wo, dg, wi); break;
      case MATERIAL_METAL: c = MetalMaterial__eval((ISPCMetalMaterial*)material, brdf, wo, dg, wi); break;
      case MATERIAL_REFLECTIVE_METAL: c = ReflectiveMetalMaterial__eval((ISPCReflectiveMetalMaterial*)material, brdf, wo, dg, wi); break;
      case MATERIAL_VELVET: c = VelvetMaterial__eval((ISPCVelvetMaterial*)material, brdf, wo, dg, wi); break;
      case MATERIAL_DIELECTRIC: c = DielectricMaterial__eval((ISPCDielectricMaterial*)material, brdf, wo, dg, wi); break;
      case MATERIAL_METALLIC_PAINT: c = MetallicPaintMaterial__eval((ISPCMetallicPaintMaterial*)material, brdf, wo, dg, wi); break;
      case MATERIAL_MATTE: c = MatteMaterial__eval((ISPCMatteMaterial*)material, brdf, wo, dg, wi); break;
      case MATERIAL_MIRROR: c = MirrorMaterial__eval((ISPCMirrorMaterial*)material, brdf, wo, dg, wi); break;
      case MATERIAL_THIN_DIELECTRIC: c = ThinDielectricMaterial__eval((ISPCThinDielectricMaterial*)material, brdf, wo, dg, wi); break;
      case MATERIAL_HAIR: c = HairMaterial__eval((ISPCHairMaterial*)material, brdf, wo, dg, wi); break;
      default: c = Vec3fa(0.0f);
      }
    }
  }
  return c;
}

inline Vec3fa Material__sample(ISPCMaterial** materials, unsigned int materialID, unsigned int numMaterials, const BRDF& brdf, const Vec3fa& Lw, const Vec3fa& wo, const DifferentialGeometry& dg, Sample3f& wi_o, Medium& medium, const Vec2f& s)
{
  Vec3fa c = Vec3fa(0.0f);
  auto id = materialID;
  {
    if (id < numMaterials) // FIXME: workaround for ISPC bug, location reached with empty execution mask
    {
      ISPCMaterial* material = materials[id];
      switch (material->type) {
      case MATERIAL_OBJ  : c = OBJMaterial__sample  ((ISPCOBJMaterial*)  material, brdf, Lw, wo, dg, wi_o, medium, s); break;
      case MATERIAL_METAL: c = MetalMaterial__sample((ISPCMetalMaterial*)material, brdf, Lw, wo, dg, wi_o, medium, s); break;
      case MATERIAL_REFLECTIVE_METAL: c = ReflectiveMetalMaterial__sample((ISPCReflectiveMetalMaterial*)material, brdf, Lw, wo, dg, wi_o, medium, s); break;
      case MATERIAL_VELVET: c = VelvetMaterial__sample((ISPCVelvetMaterial*)material, brdf, Lw, wo, dg, wi_o, medium, s); break;
      case MATERIAL_DIELECTRIC: c = DielectricMaterial__sample((ISPCDielectricMaterial*)material, brdf, Lw, wo, dg, wi_o, medium, s); break;
      case MATERIAL_METALLIC_PAINT: c = MetallicPaintMaterial__sample((ISPCMetallicPaintMaterial*)material, brdf, Lw, wo, dg, wi_o, medium, s); break;
      case MATERIAL_MATTE: c = MatteMaterial__sample((ISPCMatteMaterial*)material, brdf, Lw, wo, dg, wi_o, medium, s); break;
      case MATERIAL_MIRROR: c = MirrorMaterial__sample((ISPCMirrorMaterial*)material, brdf, Lw, wo, dg, wi_o, medium, s); break;
      case MATERIAL_THIN_DIELECTRIC: c = ThinDielectricMaterial__sample((ISPCThinDielectricMaterial*)material, brdf, Lw, wo, dg, wi_o, medium, s); break;
      case MATERIAL_HAIR: c = HairMaterial__sample((ISPCHairMaterial*)material, brdf, Lw, wo, dg, wi_o, medium, s); break;
      default: wi_o = make_Sample3f(Vec3fa(0.0f),0.0f); c = Vec3fa(0.0f); break;
      }
    }
  }
  return c;
}


////////////////////////////////////////////////////////////////////////////////
//                               Scene                                        //
////////////////////////////////////////////////////////////////////////////////

/* scene data */
RTCScene g_scene = nullptr;

/* accumulation buffer */
Vec3fa g_accu_vx;
Vec3fa g_accu_vy;
Vec3fa g_accu_vz;
Vec3fa g_accu_p;

#if 0
void device_key_pressed_handler(int key)
{
  if (key == 32  /* */) g_animation = !g_animation;
  if (key == 110 /*n*/) { g_use_smooth_normals = !g_use_smooth_normals; g_changed = true; }
  else device_key_pressed_default(key);
}
#endif

void assignShaders(ISPCGeometry* geometry)
{
#if ENABLE_FILTER_FUNCTION
  RTCGeometry geom = geometry->geometry;
  if (geometry->type == SUBDIV_MESH ||
      geometry->type == TRIANGLE_MESH ||
      geometry->type == QUAD_MESH ||
      geometry->type == GRID_MESH)
  {
    //rtcSetGeometryOccludedFilterFunction(geom,data.occlusionFilterOpaque);
    rtcSetGeometryEnableFilterFunctionFromArguments(geom,false);
  }
  else if (geometry->type == CURVES) {
    rtcSetGeometryOccludedFilterFunction(geom,data.occlusionFilterHair);
    rtcSetGeometryEnableFilterFunctionFromArguments(geom,true);
  }
#endif
}

typedef ISPCInstance* ISPCInstance_ptr;
typedef ISPCGeometry* ISPCGeometry_ptr;

RTCScene convertScene(ISPCScene* scene_in)
{
  for (unsigned int i=0; i<scene_in->numGeometries; i++)
  {
    ISPCGeometry* geometry = scene_in->geometries[i];
    if (geometry->type == SUBDIV_MESH) {
      g_subdiv_mode = true; break;
    }
  }

  assignShadersFunc = assignShaders;

  RTCScene scene_out = ConvertScene(g_device, g_ispc_scene, RTC_BUILD_QUALITY_MEDIUM, RTC_SCENE_FLAG_NONE, &g_used_features);
#if ENABLE_FILTER_FUNCTION
#if USE_ARGUMENT_CALLBACKS
  g_used_features = (RTCFeatureFlags)(g_used_features | RTC_FEATURE_FLAG_FILTER_FUNCTION_IN_ARGUMENTS);
#else
  g_used_features = (RTCFeatureFlags)(g_used_features | RTC_FEATURE_FLAG_FILTER_FUNCTION_IN_GEOMETRY);
#endif
#endif

  /* commit changes to scene */
  //progressStart();
  //rtcSetSceneProgressMonitorFunction(scene_out,progressMonitor,nullptr);
  rtcCommitScene (scene_out);
  //rtcSetSceneProgressMonitorFunction(scene_out,nullptr,nullptr);
  //progressEnd();

  return scene_out;
} // convertScene

inline Vec3fa face_forward(const Vec3fa& dir, const Vec3fa& _Ng) {
  const Vec3fa Ng = _Ng;
  return dot(dir,Ng) < 0.0f ? Ng : neg(Ng);
}

inline Vec3fa derivBezier(const ISPCHairSet* mesh, const unsigned int primID, const float t, const float time)
{
  Vec3fa p00, p01, p02, p03;
  const int i = mesh->hairs[primID].vertex;
  
  if (mesh->numTimeSteps == 1)
  {
    p00 = mesh->positions[0][i+0];
    p01 = mesh->positions[0][i+1];
    p02 = mesh->positions[0][i+2];
    p03 = mesh->positions[0][i+3];
  }
  else
  {
    float f = mesh->numTimeSteps*time;
    int itime = clamp((int)floor(f),0,(int)mesh->numTimeSteps-2);
    float t1 = f-itime;
    float t0 = 1.0f-t1;
    const Vec3fa a0 = mesh->positions[itime+0][i+0];
    const Vec3fa a1 = mesh->positions[itime+0][i+1];
    const Vec3fa a2 = mesh->positions[itime+0][i+2];
    const Vec3fa a3 = mesh->positions[itime+0][i+3];
    const Vec3fa b0 = mesh->positions[itime+1][i+0];
    const Vec3fa b1 = mesh->positions[itime+1][i+1];
    const Vec3fa b2 = mesh->positions[itime+1][i+2];
    const Vec3fa b3 = mesh->positions[itime+1][i+3];
    p00 = t0*a0 + t1*b0;
    p01 = t0*a1 + t1*b1;
    p02 = t0*a2 + t1*b2;
    p03 = t0*a3 + t1*b3;
  }

  const float t0 = 1.0f - t, t1 = t;
  const Vec3fa p10 = p00 * t0 + p01 * t1;
  const Vec3fa p11 = p01 * t0 + p02 * t1;
  const Vec3fa p12 = p02 * t0 + p03 * t1;
  const Vec3fa p20 = p10 * t0 + p11 * t1;
  const Vec3fa p21 = p11 * t0 + p12 * t1;
  //const Vec3fa p30 = p20 * t0 + p21 * t1;
  return Vec3fa(3.0f*(p21-p20));
}

inline Vec3fa derivHermite(const ISPCHairSet* mesh, const unsigned int primID, const float u, const float time)
{
  Vec3fa p0, p1, t0, t1;
  const int i = mesh->hairs[primID].vertex;
  
  if (mesh->numTimeSteps == 1)
  {
    p0 = mesh->positions[0][i+0];
    p1 = mesh->positions[0][i+1];
    t0 = mesh->tangents[0][i+0];
    t1 = mesh->tangents[0][i+1];
  }
  else
  {
    float f = mesh->numTimeSteps*time;
    int itime = clamp((int)floor(f),0,(int)mesh->numTimeSteps-2);
    float time1 = f-itime;
    float time0 = 1.0f-time1;
    const Vec3fa ap0 = mesh->positions[itime+0][i+0];
    const Vec3fa ap1 = mesh->positions[itime+0][i+1];
    const Vec3fa at0 = mesh->tangents[itime+0][i+0];
    const Vec3fa at1 = mesh->tangents[itime+0][i+1];
    const Vec3fa bp0 = mesh->positions[itime+1][i+0];
    const Vec3fa bp1 = mesh->positions[itime+1][i+1];
    const Vec3fa bt0 = mesh->tangents[itime+1][i+0];
    const Vec3fa bt1 = mesh->tangents[itime+1][i+1];
    p0 = time0*ap0 + time1*bp0;
    p1 = time0*ap1 + time1*bp1;
    t0 = time0*at0 + time1*bt0;
    t1 = time0*at1 + time1*bt1;
  }
  const Vec3fa p00 = p0;
  const Vec3fa p01 = p0+(1.0f/3.0f)*t0;
  const Vec3fa p02 = p1-(1.0f/3.0f)*t1;
  const Vec3fa p03 = p1;
    
  const float u0 = 1.0f - u, u1 = u;
  const Vec3fa p10 = p00 * u0 + p01 * u1;
  const Vec3fa p11 = p01 * u0 + p02 * u1;
  const Vec3fa p12 = p02 * u0 + p03 * u1;
  const Vec3fa p20 = p10 * u0 + p11 * u1;
  const Vec3fa p21 = p11 * u0 + p12 * u1;
  //const Vec3fa p30 = p20 * u0 + p21 * u1;
  return Vec3fa(3.0f*(p21-p20));
}

inline Vec3fa derivBSpline(const ISPCHairSet* mesh, const unsigned int primID, const float t, const float time)
{
  Vec3fa p00, p01, p02, p03;
  const int i = mesh->hairs[primID].vertex;
  
  if (mesh->numTimeSteps == 1)
  {
    p00 = mesh->positions[0][i+0];
    p01 = mesh->positions[0][i+1];
    p02 = mesh->positions[0][i+2];
    p03 = mesh->positions[0][i+3];
  }
  else
  {
    float f = mesh->numTimeSteps*time;
    int itime = clamp((int)floor(f),0,(int)mesh->numTimeSteps-2);
    float t1 = f-itime;
    float t0 = 1.0f-t1;
    const Vec3fa a0 = mesh->positions[itime+0][i+0];
    const Vec3fa a1 = mesh->positions[itime+0][i+1];
    const Vec3fa a2 = mesh->positions[itime+0][i+2];
    const Vec3fa a3 = mesh->positions[itime+0][i+3];
    const Vec3fa b0 = mesh->positions[itime+1][i+0];
    const Vec3fa b1 = mesh->positions[itime+1][i+1];
    const Vec3fa b2 = mesh->positions[itime+1][i+2];
    const Vec3fa b3 = mesh->positions[itime+1][i+3];
    p00 = t0*a0 + t1*b0;
    p01 = t0*a1 + t1*b1;
    p02 = t0*a2 + t1*b2;
    p03 = t0*a3 + t1*b3;
  }

  const float t0 = 1.0f - t, t1 = t;
  const float n0 = -0.5f*t1*t1;
  const float n1 = -0.5f*t0*t0 - 2.0f*(t0*t1);
  const float n2 =  0.5f*t1*t1 + 2.0f*(t1*t0);
  const float n3 =  0.5f*t0*t0;
  return Vec3fa(n0*p00 + n1*p01 + n2*p02 + n3*p03);
}

void postIntersectGeometry(const TutorialData& data, const Ray& ray, DifferentialGeometry& dg, ISPCGeometry* geometry, int& materialID)
{
  if (geometry->type == TRIANGLE_MESH)
  {
    ISPCTriangleMesh* mesh = (ISPCTriangleMesh*) geometry;
    materialID = mesh->geom.materialID;

    ISPCTriangle* tri = &mesh->triangles[dg.primID];
    const Vec3fa p0 = Vec3fa(mesh->positions[0][tri->v0]);
    const Vec3fa p1 = Vec3fa(mesh->positions[0][tri->v1]);
    const Vec3fa p2 = Vec3fa(mesh->positions[0][tri->v2]);
    const Vec3fa e = max(max(abs(p0),abs(p1)),max(abs(p2),abs(ray.org)));
    dg.eps = 32.0f*1.19209e-07f*max(max(e.x,e.y),max(e.z,ray.tfar));
    
    if (mesh->texcoords)
    {
      ISPCTriangle* tri = &mesh->triangles[dg.primID];
      const Vec2f st0 = mesh->texcoords[tri->v0];
      const Vec2f st1 = mesh->texcoords[tri->v1];
      const Vec2f st2 = mesh->texcoords[tri->v2];
      const float u = ray.u, v = ray.v, w = 1.0f-ray.u-ray.v;
      const Vec2f st = w*st0 + u*st1 + v*st2;
      dg.u = st.x;
      dg.v = st.y;
    }
    if (mesh->normals)
    {
      if (mesh->numTimeSteps == 1)
      {
        ISPCTriangle* tri = &mesh->triangles[dg.primID];
        const Vec3fa n0 = Vec3fa(mesh->normals[0][tri->v0]);
        const Vec3fa n1 = Vec3fa(mesh->normals[0][tri->v1]);
        const Vec3fa n2 = Vec3fa(mesh->normals[0][tri->v2]);
        const float u = ray.u, v = ray.v, w = 1.0f-ray.u-ray.v;
        dg.Ns = w*n0 + u*n1 + v*n2;
      }
      else
      {
        ISPCTriangle* tri = &mesh->triangles[dg.primID];
        float f = mesh->numTimeSteps*ray.time();
        int itime = clamp((int)floor(f),0,(int)mesh->numTimeSteps-2);
        float t1 = f-itime;
        float t0 = 1.0f-t1;
        const Vec3fa a0 = Vec3fa(mesh->normals[itime+0][tri->v0]);
        const Vec3fa a1 = Vec3fa(mesh->normals[itime+0][tri->v1]);
        const Vec3fa a2 = Vec3fa(mesh->normals[itime+0][tri->v2]);
        const Vec3fa b0 = Vec3fa(mesh->normals[itime+1][tri->v0]);
        const Vec3fa b1 = Vec3fa(mesh->normals[itime+1][tri->v1]);
        const Vec3fa b2 = Vec3fa(mesh->normals[itime+1][tri->v2]);
        const Vec3fa n0 = t0*a0 + t1*b0;
        const Vec3fa n1 = t0*a1 + t1*b1;
        const Vec3fa n2 = t0*a2 + t1*b2;
        const float u = ray.u, v = ray.v, w = 1.0f-ray.u-ray.v;
        dg.Ns = w*n0 + u*n1 + v*n2;
      }
    }
  }
  else if (geometry->type == QUAD_MESH)
  {
    ISPCQuadMesh* mesh = (ISPCQuadMesh*) geometry;
    materialID = mesh->geom.materialID;

    ISPCQuad* quad = &mesh->quads[dg.primID];
    const Vec3fa p0 = Vec3fa(mesh->positions[0][quad->v0]);
    const Vec3fa p1 = Vec3fa(mesh->positions[0][quad->v1]);
    const Vec3fa p2 = Vec3fa(mesh->positions[0][quad->v2]);
    const Vec3fa p3 = Vec3fa(mesh->positions[0][quad->v3]);
    const Vec3fa e = max(max(max(abs(p0),abs(p1)),max(abs(p2),abs(p3))),abs(ray.org));
    dg.eps = 32.0f*1.19209e-07f*max(max(e.x,e.y),max(e.z,ray.tfar));
    
    if (mesh->texcoords)
    {
      ISPCQuad* quad = &mesh->quads[dg.primID];
      const Vec2f st0 = mesh->texcoords[quad->v0];
      const Vec2f st1 = mesh->texcoords[quad->v1];
      const Vec2f st2 = mesh->texcoords[quad->v2];
      const Vec2f st3 = mesh->texcoords[quad->v3];
      if (ray.u+ray.v < 1.0f) {
        const float u = ray.u, v = ray.v; const float w = 1.0f-u-v;
        const Vec2f st = w*st0 + u*st1 + v*st3;
        dg.u = st.x;
        dg.v = st.y;
      } else {
        const float u = 1.0f-ray.u, v = 1.0f-ray.v; const float w = 1.0f-u-v;
        const Vec2f st = w*st2 + u*st3 + v*st1;
        dg.u = st.x;
        dg.v = st.y;
      }
    }
    if (mesh->normals)
    {
      if (mesh->numTimeSteps == 1)
      {
        ISPCQuad* quad = &mesh->quads[dg.primID];
        const Vec3fa n0 = Vec3fa(mesh->normals[0][quad->v0]);
        const Vec3fa n1 = Vec3fa(mesh->normals[0][quad->v1]);
        const Vec3fa n2 = Vec3fa(mesh->normals[0][quad->v2]);
        const Vec3fa n3 = Vec3fa(mesh->normals[0][quad->v3]);
        if (ray.u+ray.v < 1.0f) {
          const float u = ray.u, v = ray.v; const float w = 1.0f-u-v;
          dg.Ns = w*n0 + u*n1 + v*n3;
        } else {
          const float u = 1.0f-ray.u, v = 1.0f-ray.v; const float w = 1.0f-u-v;
          dg.Ns = w*n2 + u*n3 + v*n1;
        }
      }
      else
      {
        ISPCQuad* quad = &mesh->quads[dg.primID];
        float f = mesh->numTimeSteps*ray.time();
        int itime = clamp((int)floor(f),0,(int)mesh->numTimeSteps-2);
        float t1 = f-itime;
        float t0 = 1.0f-t1;
        const Vec3fa a0 = Vec3fa(mesh->normals[itime+0][quad->v0]);
        const Vec3fa a1 = Vec3fa(mesh->normals[itime+0][quad->v1]);
        const Vec3fa a2 = Vec3fa(mesh->normals[itime+0][quad->v2]);
        const Vec3fa a3 = Vec3fa(mesh->normals[itime+0][quad->v3]);
        const Vec3fa b0 = Vec3fa(mesh->normals[itime+1][quad->v0]);
        const Vec3fa b1 = Vec3fa(mesh->normals[itime+1][quad->v1]);
        const Vec3fa b2 = Vec3fa(mesh->normals[itime+1][quad->v2]);
        const Vec3fa b3 = Vec3fa(mesh->normals[itime+1][quad->v3]);
        const Vec3fa n0 = t0*a0 + t1*b0;
        const Vec3fa n1 = t0*a1 + t1*b1;
        const Vec3fa n2 = t0*a2 + t1*b2;
        const Vec3fa n3 = t0*a3 + t1*b3;
        if (ray.u+ray.v < 1.0f) {
          const float u = ray.u, v = ray.v; const float w = 1.0f-u-v;
          dg.Ns = w*n0 + u*n1 + v*n3;
        } else {
          const float u = 1.0f-ray.u, v = 1.0f-ray.v; const float w = 1.0f-u-v;
          dg.Ns = w*n2 + u*n3 + v*n1;
        }
      }
    }
  }
#if !defined(__SYCL_DEVICE_ONLY__)
  else if (geometry->type == SUBDIV_MESH)
  {
    ISPCSubdivMesh* mesh = (ISPCSubdivMesh*) geometry;
    materialID = mesh->geom.materialID;

    if (data.use_smooth_normals)
    {
      Vec3fa dPdu,dPdv;
      rtcInterpolate1(mesh->geom.geometry,dg.primID,dg.u,dg.v,RTC_BUFFER_TYPE_VERTEX,0,nullptr,&dPdu.x,&dPdv.x,3);
      dg.Ns = normalize(cross(dPdv,dPdu));
    }
    
    //const Vec2f st = getTextureCoordinatesSubdivMesh(mesh,dg.primID,ray.u,ray.v);
    //dg.u = st.x;
    //dg.v = st.y;
    dg.u = 0;
    dg.v = 0;
  }
#endif
  else if (geometry->type == GRID_MESH)
  {
    ISPCGridMesh* mesh = (ISPCGridMesh*) geometry;
    materialID = mesh->geom.materialID;
  }
  else if (geometry->type == POINTS)
  {
    ISPCPointSet* mesh = (ISPCPointSet*) geometry;
    materialID = mesh->geom.materialID;
  }
  else if (geometry->type == CURVES)
  {
    ISPCHairSet* mesh = (ISPCHairSet*) geometry;
    materialID = mesh->geom.materialID;
    
    if (mesh->type == RTC_GEOMETRY_TYPE_FLAT_LINEAR_CURVE)
    {
      dg.Tx = normalize(dg.Ng);
      dg.Ty = normalize(cross(neg(ray.dir),dg.Tx));
      dg.Ng = normalize(cross(dg.Ty,dg.Tx));
    }
    else if (mesh->type == RTC_GEOMETRY_TYPE_ROUND_BEZIER_CURVE)
    {
      Vec3fa dp = derivBezier(mesh,dg.primID,ray.u,ray.time());
      if (reduce_max(abs(dp)) < 1E-6f) dp = Vec3fa(1,1,1);
      dg.Tx = normalize(Vec3fa(dp));
      dg.Ty = normalize(cross(Vec3fa(dp),dg.Ng));
      dg.Ng = dg.Ns = normalize(dg.Ng);
      dg.eps = 1024.0f*1.19209e-07f*max(max(abs(dg.P.x),abs(dg.P.y)),max(abs(dg.P.z),ray.tfar));
    }
    else if (mesh->type == RTC_GEOMETRY_TYPE_FLAT_BEZIER_CURVE)
    {
      Vec3fa dp = derivBezier(mesh,dg.primID,ray.u,ray.time());
      if (reduce_max(abs(dp)) < 1E-6f) dp = Vec3fa(1,1,1);
      dg.Tx = normalize(dp);
      dg.Ty = normalize(cross(neg(ray.dir),dg.Tx));
      dg.Ng = dg.Ns = normalize(cross(dg.Ty,dg.Tx));
    }
    else if (mesh->type == RTC_GEOMETRY_TYPE_ROUND_BSPLINE_CURVE)
    {
      Vec3fa dp = derivBSpline(mesh,dg.primID,ray.u,ray.time());
      if (reduce_max(abs(dp)) < 1E-6f) dp = Vec3fa(1,1,1);
      dg.Tx = normalize(Vec3fa(dp));
      dg.Ty = normalize(cross(Vec3fa(dp),dg.Ng));
      dg.Ng = dg.Ns = normalize(dg.Ng);
      dg.eps = 1024.0f*1.19209e-07f*max(max(abs(dg.P.x),abs(dg.P.y)),max(abs(dg.P.z),ray.tfar));
    }
    else if (mesh->type == RTC_GEOMETRY_TYPE_FLAT_BSPLINE_CURVE)
    {
      Vec3fa dp = derivBSpline(mesh,dg.primID,ray.u,ray.time());
      if (reduce_max(abs(dp)) < 1E-6f) dp = Vec3fa(1,1,1);
      dg.Tx = normalize(dp);
      dg.Ty = normalize(cross(neg(ray.dir),dg.Tx));
      dg.Ng = dg.Ns = normalize(cross(dg.Ty,dg.Tx));
    }
    else if (mesh->type == RTC_GEOMETRY_TYPE_ROUND_HERMITE_CURVE)
    {
      Vec3fa dp = derivHermite(mesh,dg.primID,ray.u,ray.time());
      if (reduce_max(abs(dp)) < 1E-6f) dp = Vec3fa(1,1,1);
      dg.Tx = normalize(Vec3fa(dp));
      dg.Ty = normalize(cross(Vec3fa(dp),dg.Ng));
      dg.Ng = dg.Ns = normalize(dg.Ng);
      dg.eps = 1024.0f*1.19209e-07f*max(max(abs(dg.P.x),abs(dg.P.y)),max(abs(dg.P.z),ray.tfar));
    }
    else if (mesh->type == RTC_GEOMETRY_TYPE_FLAT_HERMITE_CURVE)
    {
      Vec3fa dp = derivHermite(mesh,dg.primID,ray.u,ray.time());
      if (reduce_max(abs(dp)) < 1E-6f) dp = Vec3fa(1,1,1);
      dg.Tx = normalize(dp);
      dg.Ty = normalize(cross(neg(ray.dir),dg.Tx));
      dg.Ng = dg.Ns = normalize(cross(dg.Ty,dg.Tx));
    }
  }
  else
    assert(false);

  if (max(max(abs(dg.Ns.x), abs(dg.Ns.y)), abs(dg.Ns.z)) < 1E-4f)
    dg.Ns = Vec3fa(1, 0, 0);
}

AffineSpace3fa calculate_interpolated_space (ISPCInstance* instance, float gtime)
{
  if (instance->numTimeSteps == 1)
    return AffineSpace3fa(instance->spaces[0]);

  /* calculate time segment itime and fractional time ftime */
  const int time_segments = instance->numTimeSteps-1;
  const float time = gtime*(float)(time_segments);
  const int itime = clamp((int)(floor(time)),(int)0,time_segments-1);
  const float ftime = time - (float)(itime);
  return (1.0f-ftime)*AffineSpace3fa(instance->spaces[itime+0]) + ftime*AffineSpace3fa(instance->spaces[itime+1]);
}

typedef ISPCInstance* ISPCInstancePtr;

inline int postIntersect(const TutorialData& data, const Ray& ray, DifferentialGeometry& dg)
{
  dg.eps = 32.0f*1.19209e-07f*max(max(abs(dg.P.x),abs(dg.P.y)),max(abs(dg.P.z),ray.tfar));
   
  AffineSpace3fa local2world = AffineSpace3fa::scale(Vec3fa(1));
  ISPCGeometry** geometries = data.ispc_scene->geometries;
  
  for (int i=0; i<RTC_MAX_INSTANCE_LEVEL_COUNT; i++)
  {
    const unsigned int instID = dg.instIDs[i];
    if (instID == -1) break;

    ISPCInstance* instance = (ISPCInstancePtr) geometries[instID];
    local2world = local2world * calculate_interpolated_space(instance,ray.time());

    assert(instance->child->type == GROUP);
    geometries = ((ISPCGroup*)instance->child)->geometries;
  }

  int materialID = 0;
  ISPCGeometry* geom = geometries[dg.geomID];
  auto g = geom; {
    postIntersectGeometry(data,ray,dg,g,materialID);
  }
  dg.Ng = xfmVector(local2world,dg.Ng);
  dg.Ns = xfmVector(local2world,dg.Ns);
  
  return materialID;
}

RTC_SYCL_INDIRECTLY_CALLABLE void occlusionFilterOpaque(const RTCFilterFunctionNArguments* args)
{
  RayQueryContext* context = (RayQueryContext*) args->context;
  Vec3fa* transparency = (Vec3fa*) context->userRayExt;
  if (!transparency) return;
  
  int* valid_i = args->valid;
  
  assert(args->N == 1);
  bool valid = *((int*) valid_i);
  if (!valid) return;
   
  *transparency = Vec3fa(0.0f);
}

/* occlusion filter function */
RTC_SYCL_INDIRECTLY_CALLABLE void occlusionFilterHair(const RTCFilterFunctionNArguments* args)
{
  RayQueryContext* context = (RayQueryContext*) args->context;
  TutorialData* pdata = (TutorialData*) context->tutorialData;
  TutorialData& data = *pdata;
  Vec3fa* transparency = (Vec3fa*) context->userRayExt;
  if (!transparency) return;
  
  int* valid_i = args->valid;
  struct RTCHitN* hit = args->hit;
  const unsigned int N = args->N;
  
  assert(N == 1);
  bool valid = *((int*) valid_i);
  if (!valid) return;
  
  const unsigned int rayID = 0;
  
  unsigned int hit_geomID = RTCHitN_geomID(hit,N,rayID);
  Vec3fa Kt = Vec3fa(0.0f);
  auto geomID = hit_geomID;
  {
    ISPCGeometry* geometry = data.ispc_scene->geometries[geomID];
    if (geometry->type == CURVES)
    {
      int materialID = ((ISPCHairSet*)geometry)->geom.materialID;
      ISPCMaterial* material = data.ispc_scene->materials[materialID];
      switch (material->type) {
      case MATERIAL_HAIR: Kt = Vec3fa(((ISPCHairMaterial*)material)->Kt); break;
      default: break;
      }
    }
  }

  Kt = Kt * *transparency;
  *transparency = Kt;
  if (max(max(transparency->x,transparency->y),transparency->z) > 0.0f)
    valid_i[0] = 0;
}

RTC_SYCL_INDIRECTLY_CALLABLE void contextFilterFunction(const RTCFilterFunctionNArguments* args)
{
  RayQueryContext* context = (RayQueryContext*) args->context;
  TutorialData* pdata = (TutorialData*) context->tutorialData;
  TutorialData& data = *pdata;
  int* valid_i = args->valid;

  bool valid = *((int*) valid_i);
  if (!valid) return;

  RTCHit* potential_hit = (RTCHit*) args->hit;
  if (potential_hit->instID[0] == -1)
  {
    unsigned int geomID = potential_hit->geomID;
    ISPCGeometry* geometry = data.ispc_scene->geometries[geomID];
    
    if (geometry->type == SUBDIV_MESH ||
        geometry->type == TRIANGLE_MESH ||
        geometry->type == QUAD_MESH ||
        geometry->type == GRID_MESH)
    {
      //occlusionFilterOpaque(args);
    }
    else if (geometry->type == CURVES)
    {
      occlusionFilterHair(args);
    }
  }
}

Vec3fa renderPixelFunction(const TutorialData& data, float x, float y, RandomSampler& sampler, const ISPCCamera& camera, RayStats& stats, const RTCFeatureFlags features)
{
  /* radiance accumulator and weight */
  Vec3fa L = Vec3fa(0.0f);
  Vec3fa Lw = Vec3fa(1.0f);
  Medium medium = make_Medium_Vacuum();
  float time = RandomSampler_get1D(sampler);

  /* initialize ray */
  Ray ray(Vec3fa(camera.xfm.p),
                     Vec3fa(normalize(x*camera.xfm.l.vx + y*camera.xfm.l.vy + camera.xfm.l.vz)),0.0f,inf,time);

  DifferentialGeometry dg;
 
  /* iterative path tracer loop */
  for (int i=0; i<data.max_path_length; i++)
  {
    /* terminate if contribution too low */
    if (max(Lw.x,max(Lw.y,Lw.z)) < 0.01f)
      break;

    /* intersect ray with scene */
    RayQueryContext context;
    InitIntersectionContext(&context);
    context.tutorialData = (void*) &data;
    
    RTCIntersectArguments args;
    rtcInitIntersectArguments(&args);
    args.context = &context.context;
    args.flags = (i == 0) ? data.iflags_coherent : data.iflags_incoherent;
    args.feature_mask = features;
#if USE_ARGUMENT_CALLBACKS && ENABLE_FILTER_FUNCTION
    args.filter = nullptr;
#endif
  
    rtcIntersect1(data.scene,RTCRayHit_(ray),&args);
    RayStats_addRay(stats);
    const Vec3fa wo = neg(ray.dir);

    /* invoke environment lights if nothing hit */
    if (ray.geomID == RTC_INVALID_GEOMETRY_ID)
    {
      //L = L + Lw*Vec3fa(1.0f);

      /* iterate over all lights */
      for (unsigned int i=0; i<data.ispc_scene->numLights; i++)
      {
        const Light* l = data.ispc_scene->lights[i];
        //Light_EvalRes le = l->eval(l,dg,ray.dir);
        Light_EvalRes le = Lights_eval(l,dg,ray.dir);
        L = L + Lw*le.value;
      }

      break;
    }

    Vec3fa Ns = normalize(ray.Ng);

    /* compute differential geometry */
    for (int i=0; i<RTC_MAX_INSTANCE_LEVEL_COUNT; i++)
      dg.instIDs[i] = ray.instID[i];
    
    dg.geomID = ray.geomID;
    dg.primID = ray.primID;
    dg.u = ray.u;
    dg.v = ray.v;
    dg.P  = ray.org+ray.tfar*ray.dir;
    dg.Ng = ray.Ng;
    dg.Ns = Ns;
    int materialID = postIntersect(data,ray,dg);
    dg.Ng = face_forward(ray.dir,normalize(dg.Ng));
    dg.Ns = face_forward(ray.dir,normalize(dg.Ns));

    /*! Compute  simple volumetric effect. */
    Vec3fa c = Vec3fa(1.0f);
    const Vec3fa transmission = medium.transmission;
    if (ne(transmission,Vec3fa(1.0f)))
      c = c * pow(transmission,ray.tfar);

    /* calculate BRDF */
    BRDF brdf;
    int numMaterials = data.ispc_scene->numMaterials;
    ISPCMaterial** material_array = &data.ispc_scene->materials[0];
    Material__preprocess(material_array,materialID,numMaterials,brdf,wo,dg,medium);

    /* sample BRDF at hit point */
    Sample3f wi1;
    c = c * Material__sample(material_array,materialID,numMaterials,brdf,Lw, wo, dg, wi1, medium, RandomSampler_get2D(sampler));

    /* iterate over lights */
    for (unsigned int i=0; i<data.ispc_scene->numLights; i++)
    {
      const Light* l = data.ispc_scene->lights[i];
      //Light_SampleRes ls = l->sample(l,dg,RandomSampler_get2D(sampler));
      Light_SampleRes ls = Lights_sample(l,dg,RandomSampler_get2D(sampler));
      if (ls.pdf <= 0.0f) continue;
      Vec3fa transparency = Vec3fa(1.0f);
      Ray shadow(dg.P,ls.dir,dg.eps,ls.dist,time);
      context.userRayExt = &transparency;

      RTCOccludedArguments sargs;
      rtcInitOccludedArguments(&sargs);
      sargs.context = &context.context;
      sargs.flags = data.iflags_incoherent;
      sargs.feature_mask = features;
#if USE_ARGUMENT_CALLBACKS && ENABLE_FILTER_FUNCTION
      sargs.filter = contextFilterFunction;
#endif
      rtcOccluded1(data.scene,RTCRay_(shadow),&sargs);
      RayStats_addShadowRay(stats);
#if !ENABLE_FILTER_FUNCTION
      if (shadow.tfar > 0.0f)
#else
      if (shadow.tfar < 0.0f) transparency = Vec3fa(0.0f);
      if (max(max(transparency.x,transparency.y),transparency.z) > 0.0f)
#endif
        L = L + Lw*ls.weight*transparency*Material__eval(material_array,materialID,numMaterials,brdf,wo,dg,ls.dir);
    }

    if (wi1.pdf <= 1E-4f /* 0.0f */) break;
    Lw = Lw*c/wi1.pdf;

    /* setup secondary ray */
    float sign = dot(wi1.v,dg.Ng) < 0.0f ? -1.0f : 1.0f;
    dg.P = dg.P + sign*dg.eps*dg.Ng;
    init_Ray(ray, dg.P,normalize(wi1.v),dg.eps,inf,time);
  }
  return L;
}

/* task that renders a single screen tile */
void renderPixelStandard(const TutorialData& data,
                         int x, int y,
                         int* pixels,
                         const unsigned int width,
                         const unsigned int height,
                         const float time,
                         const ISPCCamera& camera,
                         RayStats& stats,
                         const RTCFeatureFlags features)
{
  RandomSampler sampler;

  Vec3fa L = Vec3fa(0.0f);

  for (int i=0; i<data.spp; i++)
  {
    RandomSampler_init(sampler, x, y, data.accu_count*data.spp+i);

    /* calculate pixel color */
    float fx = x + RandomSampler_get1D(sampler);
    float fy = y + RandomSampler_get1D(sampler);
    L = L + renderPixelFunction(data,fx,fy,sampler,camera,stats,features);
  }
  L = L/(float)data.spp;

  /* write color to framebuffer */
  Vec3ff accu_color = data.accu[y*width+x] + Vec3ff(L.x,L.y,L.z,1.0f); data.accu[y*width+x] = accu_color;
  float f = rcp(max(0.001f,accu_color.w));
  unsigned int r = (unsigned int) (255.01f * clamp(accu_color.x*f,0.0f,1.0f));
  unsigned int g = (unsigned int) (255.01f * clamp(accu_color.y*f,0.0f,1.0f));
  unsigned int b = (unsigned int) (255.01f * clamp(accu_color.z*f,0.0f,1.0f));
  pixels[y*width+x] = (b << 16) + (g << 8) + r;
}

/* task that renders a single screen tile */
void renderTileTask (int taskIndex, int threadIndex, int* pixels,
                         const unsigned int width,
                         const unsigned int height,
                         const float time,
                         const ISPCCamera& camera,
                         const int numTilesX,
                         const int numTilesY)
{
  const int t = taskIndex;
  const unsigned int tileY = t / numTilesX;
  const unsigned int tileX = t - tileY * numTilesX;
  const unsigned int x0 = tileX * TILE_SIZE_X;
  const unsigned int x1 = min(x0+TILE_SIZE_X,width);
  const unsigned int y0 = tileY * TILE_SIZE_Y;
  const unsigned int y1 = min(y0+TILE_SIZE_Y,height);

  for (unsigned int y=y0; y<y1; y++) for (unsigned int x=x0; x<x1; x++)
  {
    renderPixelStandard(data,x,y,pixels,width,height,time,camera,g_stats[threadIndex],RTC_FEATURE_FLAG_ALL);
  }
}


/***************************************************************************************/

inline float updateEdgeLevel( ISPCSubdivMesh* mesh, const Vec3fa& cam_pos, const unsigned int e0, const unsigned int e1)
{
  const Vec3fa v0 = mesh->positions[0][mesh->position_indices[e0]];
  const Vec3fa v1 = mesh->positions[0][mesh->position_indices[e1]];
  const Vec3fa edge = v1-v0;
  const Vec3fa P = 0.5f*(v1+v0);
  const Vec3fa dist = Vec3fa(cam_pos) - P;
  return max(min(LEVEL_FACTOR*(0.5f*length(edge)/length(dist)),MAX_EDGE_LEVEL),MIN_EDGE_LEVEL);
}

void updateEdgeLevelBuffer( ISPCSubdivMesh* mesh, const Vec3fa& cam_pos, unsigned int startID, unsigned int endID )
{
  for (unsigned int f=startID; f<endID;f++)
  {
    unsigned int e = mesh->face_offsets[f];
    unsigned int N = mesh->verticesPerFace[f];
    if (N == 4) /* fast path for quads */
      for (unsigned int i=0; i<4; i++)
        mesh->subdivlevel[e+i] =  updateEdgeLevel(mesh,cam_pos,e+(i+0),e+(i+1)%4);
       else if (N == 3) /* fast path for triangles */
         for (unsigned int i=0; i<3; i++)
           mesh->subdivlevel[e+i] =  updateEdgeLevel(mesh,cam_pos,e+(i+0),e+(i+1)%3);
       else /* fast path for general polygons */
         for (unsigned int i=0; i<N; i++)
           mesh->subdivlevel[e+i] =  updateEdgeLevel(mesh,cam_pos,e+(i+0),e+(i+1)%N);
  }
}

#if defined(ISPC)
void updateEdgeLevelBufferTask (int taskIndex, int threadIndex,  ISPCSubdivMesh* mesh, const Vec3fa& cam_pos )
{
  const unsigned int size = mesh->numFaces;
  const unsigned int startID = ((taskIndex+0)*size)/taskCount;
  const unsigned int endID   = ((taskIndex+1)*size)/taskCount;
  updateEdgeLevelBuffer(mesh,cam_pos,startID,endID);
}
#endif

void updateEdgeLevels(ISPCScene* scene_in, const Vec3fa& cam_pos)
{
  for (unsigned int g=0; g<scene_in->numGeometries; g++)
  {
    ISPCGeometry* geometry = g_ispc_scene->geometries[g];
    if (geometry->type != SUBDIV_MESH) continue;
    ISPCSubdivMesh* mesh = (ISPCSubdivMesh*) geometry;
#if defined(ISPC)
    parallel_for(size_t(0),size_t( (mesh->numFaces+4095)/4096 ),[&](const range<size_t>& range) {
    const int threadIndex = (int)TaskScheduler::threadIndex();
    for (size_t i=range.begin(); i<range.end(); i++)
      updateEdgeLevelBufferTask((int)i,threadIndex,mesh,cam_pos);
  }); 
#else
    updateEdgeLevelBuffer(mesh,cam_pos,0,mesh->numFaces);
#endif
    rtcUpdateGeometryBuffer(geometry->geometry,RTC_BUFFER_TYPE_LEVEL,0);
    rtcCommitGeometry(geometry->geometry);
  }
}

/* called by the C++ code for initialization */
extern "C" void device_init (char* cfg)
{
  /* initialize last seen camera */
  g_accu_vx = Vec3fa(0.0f);
  g_accu_vy = Vec3fa(0.0f);
  g_accu_vz = Vec3fa(0.0f);
  g_accu_p  = Vec3fa(0.0f);

  TutorialData_Constructor(&data);

  //data.occlusionFilterOpaque = GET_FUNCTION_POINTER(occlusionFilterOpaque);
  data.occlusionFilterHair = GET_FUNCTION_POINTER(occlusionFilterHair);
  
} // device_init

extern "C" void renderFrameStandard (int* pixels,
                          const unsigned int width,
                          const unsigned int height,
                          const float time,
                          const ISPCCamera& camera)
{
/* render image */
#if defined(EMBREE_SYCL_TUTORIAL) && !defined(EMBREE_SYCL_RT_SIMULATION)
  TutorialData ldata = data;

#if defined(USE_SPECIALIZATION_CONSTANTS)
  sycl::event event = global_gpu_queue->submit([=](sycl::handler& cgh){
    cgh.set_specialization_constant<rtc_feature_mask>(g_used_features);
    const sycl::nd_range<2> nd_range = make_nd_range(height,width);
    cgh.parallel_for(nd_range,[=](sycl::nd_item<2> item, sycl::kernel_handler kh) {
      const RTCFeatureFlags feature_mask = kh.get_specialization_constant<rtc_feature_mask>();
      const unsigned int x = item.get_global_id(1); if (x >= width ) return;
      const unsigned int y = item.get_global_id(0); if (y >= height) return;
      RayStats stats;
      renderPixelStandard(ldata,x,y,pixels,width,height,time,camera,stats,feature_mask);
    });
  });
  global_gpu_queue->wait_and_throw();
#else
  sycl::event event = global_gpu_queue->submit([=](sycl::handler& cgh) {
    const sycl::nd_range<2> nd_range = make_nd_range(height,width);
    cgh.parallel_for(nd_range,[=](sycl::nd_item<2> item) {
      const unsigned int x = item.get_global_id(1); if (x >= width ) return;
      const unsigned int y = item.get_global_id(0); if (y >= height) return;
      RayStats stats;
      const RTCFeatureFlags feature_mask = RTC_FEATURE_FLAG_ALL;
      renderPixelStandard(ldata,x,y,pixels,width,height,time,camera,stats,feature_mask);
    });
  });
  global_gpu_queue->wait_and_throw();
#endif

  const auto t0 = event.template get_profiling_info<sycl::info::event_profiling::command_start>();
  const auto t1 = event.template get_profiling_info<sycl::info::event_profiling::command_end>();
  const double dt = (t1-t0)*1E-9;
  ((ISPCCamera*)&camera)->render_time = dt;
  
#else
  const int numTilesX = (width +TILE_SIZE_X-1)/TILE_SIZE_X;
  const int numTilesY = (height+TILE_SIZE_Y-1)/TILE_SIZE_Y;
  parallel_for(size_t(0),size_t(numTilesX*numTilesY),[&](const range<size_t>& range) {
    const int threadIndex = (int)TaskScheduler::threadIndex();
    for (size_t i=range.begin(); i<range.end(); i++)
      renderTileTask((int)i,threadIndex,pixels,width,height,time,camera,numTilesX,numTilesY);
  }); 
#endif
}

/* called by the C++ code to render */
extern "C" void device_render (int* pixels,
                           const unsigned int width,
                           const unsigned int height,
                           const float time,
                           const ISPCCamera& camera)
{
  /* create scene */
  if (data.scene == nullptr) {
    data.scene = convertScene(data.ispc_scene);
    if (g_subdiv_mode) updateEdgeLevels(data.ispc_scene,camera.xfm.p);
    rtcCommitScene (data.scene);
  }

  /* create accumulator */
  if (data.accu_width != width || data.accu_height != height) {
    alignedUSMFree(data.accu);
    data.accu = (Vec3ff*) alignedUSMMalloc((width*height)*sizeof(Vec3ff),16,EMBREE_USM_SHARED_DEVICE_READ_WRITE);
    data.accu_width = width;
    data.accu_height = height;
    for (unsigned int i=0; i<width*height; i++)
      data.accu[i] = Vec3ff(0.0f);
  }

  /* reset accumulator */
  bool camera_changed = g_changed || !g_accumulate || g_animation_mode; g_changed = false;
  camera_changed |= ne(g_accu_vx,camera.xfm.l.vx); g_accu_vx = camera.xfm.l.vx;
  camera_changed |= ne(g_accu_vy,camera.xfm.l.vy); g_accu_vy = camera.xfm.l.vy;
  camera_changed |= ne(g_accu_vz,camera.xfm.l.vz); g_accu_vz = camera.xfm.l.vz;
  camera_changed |= ne(g_accu_p, camera.xfm.p);    g_accu_p  = camera.xfm.p;

  if (camera_changed)
  {
    data.accu_count=0;
    for (unsigned int i=0; i<width*height; i++)
      data.accu[i] = Vec3ff(0.0f);

    if (g_subdiv_mode) {
      updateEdgeLevels(data.ispc_scene,camera.xfm.p);
      rtcCommitScene (data.scene);
    }
  }
  else
    data.accu_count++;

  if (g_animation_mode)
      UpdateScene(g_ispc_scene, time);

} // device_render

/* called by the C++ code for cleanup */
extern "C" void device_cleanup ()
{
  TutorialData_Destructor(&data);
  
} // device_cleanup

} // namespace embree