Initial commit.

Framework/lights/quad_light.cpp

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+// Copyright 2009-2021 Intel Corporation
+// SPDX-License-Identifier: Apache-2.0
+
+#include "light.h"
+#include "helper.hpp"
+
+namespace embree {
+    struct QuadLight {
+        Light super; //!< inherited light fields
+
+        Vec3fa position; //!< world-space corner position of the light
+        Vec3fa edge1; //!< vectors to adjacent corners
+        Vec3fa edge2; //!< vectors to adjacent corners
+        Vec3fa radiance; //!< RGB color and intensity of the QuadLight
+
+        Vec3fa nnormal; //!< negated normal, the direction that the QuadLight is not emitting; normalized
+        float ppdf; // probability to sample point on light = 1/area
+    };
+
+
+    // Implementation
+    //////////////////////////////////////////////////////////////////////////////
+
+    Light_SampleRes QuadLight_sample(const Light* super,
+                                     const Sample& sp,
+                                     const Vec2f& s) {
+        const QuadLight* self = (QuadLight *) super;
+        Light_SampleRes res;
+
+        // res position on light with density ppdf = 1/area
+        // TODO: use solid angle sampling
+        const Vec3fa pos = self->position + self->edge1 * s.x + self->edge2 * s.y;
+
+        // extant light vector from the hit point
+        const Vec3fa dir = pos - sp.P;
+        const float dist = length(dir);
+
+        // normalized light vector
+        res.dir = dir / dist;
+        res.dist = dist;
+
+        // convert to pdf wrt. solid angle
+        const float cosd = dot(self->nnormal, res.dir);
+        res.pdf = self->ppdf * (dist * dist) / abs(cosd);
+
+        // emit only to one side
+        res.weight = cosd > 0.f ? self->radiance * rcp(res.pdf) : Vec3fa(0.f);
+
+        return res;
+    }
+
+    Light_EvalRes QuadLight_eval(const Light* super,
+                                 const Sample& dg,
+                                 const Vec3fa& dir) {
+        Light_EvalRes res;
+        res.value = Vec3fa(0, 0, 0);
+        res.dist = inf;
+        res.pdf = 0.f;
+        return res;
+    }
+
+
+    // Exports (called from C++)
+    //////////////////////////////////////////////////////////////////////////////
+
+    //! Set the parameters of an ispc-side QuadLight object
+    extern "C" void QuadLight_set(void* super,
+                                  const Vec3fa& position,
+                                  const Vec3fa& edge2,
+                                  const Vec3fa& edge1,
+                                  const Vec3fa& radiance) {
+        QuadLight* self = (QuadLight *) super;
+        self->position = position;
+        self->edge1 = edge1;
+        self->edge2 = edge2;
+        self->radiance = radiance;
+
+        const Vec3fa ndirection = cross(edge2, edge1);
+        self->ppdf = rcp(length(ndirection));
+        self->nnormal = ndirection * self->ppdf;
+    }
+
+    //! Create an ispc-side QuadLight object
+    extern "C" void* QuadLight_create() {
+        QuadLight* self = (QuadLight *) alignedUSMMalloc(sizeof(QuadLight), 16);
+
+        Light_Constructor(&self->super);
+        //self->super.sample = GET_FUNCTION_POINTER(QuadLight_sample);
+        self->super.type = LIGHT_QUAD;
+
+        QuadLight_set(self,
+                      Vec3fa(0.f),
+                      Vec3fa(1.f, 0.f, 0.f),
+                      Vec3fa(0.f, 1.f, 0.f),
+                      Vec3fa(1.f));
+
+        return self;
+    }
+} // namespace embree