From 0b132ea4e738a25207c15edd2e8bdd8f54888eb7 Mon Sep 17 00:00:00 2001
From: hal8174 <henning.lindemann@pm.me>
Date: Thu, 2 May 2024 12:37:21 +0200
Subject: [PATCH] Add path tracing implementation for Assignment1.

---
 Assignments/Assignment1/Application1.cpp | 86 +++++++++++++++++++++++-
 Assignments/Assignment1/Application1.h   | 28 ++++++++
 2 files changed, 111 insertions(+), 3 deletions(-)

diff --git a/Assignments/Assignment1/Application1.cpp b/Assignments/Assignment1/Application1.cpp
index cda3722..113b053 100644
--- a/Assignments/Assignment1/Application1.cpp
+++ b/Assignments/Assignment1/Application1.cpp
@@ -1,4 +1,10 @@
 #include "Application1.h"
+#include "helper.hpp"
+#include "lights/light.h"
+#include "math/vec3fa.h"
+#include "random_sampler.hpp"
+#include "ray.hpp"
+#include "sampling.hpp"
 
 void Application1::initScene() {
     Data_Constructor(&data, 1, 8);
@@ -62,8 +68,82 @@ void Application1::veachScene() {
     scene = nullptr;
 }
 
-/* task that renders a single screen tile */
 Vec3fa Application1::renderPixel(float x, float y, const ISPCCamera& camera, RayStats& stats, RandomSampler& sampler) {
+    if (selected == 0) {
+    return renderPixelOrig(x, y, camera, stats, sampler);
+    } else if (selected == 1) {
+        return renderPixelPathTracer(x, y, camera, stats, sampler);
+    } else {
+        return Vec3fa(0.0f);
+    }
+}
+
+Vec3fa Application1::renderPixelPathTracer(float x, float y, const ISPCCamera& camera, RayStats& stats, RandomSampler& sampler) {
+    /* radiance accumulator and weight */
+    Vec3fa L = Vec3fa(0.0f);
+    Vec3fa Lw = Vec3fa(1.0f);
+
+    /* 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);
+
+
+    for (int i = 0; i < ray_depth; i++) {
+        /* intersect ray with scene */
+        RTCIntersectArguments iargs;
+        rtcInitIntersectArguments(&iargs);
+        iargs.feature_mask = RTC_FEATURE_FLAG_TRIANGLE;
+        rtcIntersect1(data.g_scene, RTCRayHit_(ray), &iargs);
+        RayStats_addRay(stats);
+
+        const Vec3fa wo = neg(ray.dir);
+
+        /* shade pixels */
+        if (ray.geomID == RTC_INVALID_GEOMETRY_ID) {
+            break;
+        }
+
+        
+        Vec3fa Ns = normalize(ray.Ng);
+        Sample sample;
+        sample.P = ray.org + ray.tfar * ray.dir;
+        sample.Ng = ray.Ng;
+        sample.Ns = Ns;
+        int matId = data.scene->geometries[ray.geomID]->materialID;
+        unsigned lightID = data.scene->geometries[ray.geomID]->lightID;
+        sample.Ng = face_forward(ray.dir, normalize(sample.Ng));
+        sample.Ns = face_forward(ray.dir, normalize(sample.Ns));
+
+        if (lightID != unsigned(-1)) {
+            const Light* l = data.scene->lights[lightID];
+            Light_EvalRes evalRes = Lights_eval(l, sample, -wo);
+            L += Lw * evalRes.value;
+            break;
+        }
+
+        /* calculate BRDF */
+        BRDF brdf;
+        std::vector<Material *> material_array = data.scene->materials;
+        Material__preprocess(material_array, matId, brdf, wo, sample);
+
+        /* sample BRDF at hit point */
+
+        Vec2f uv = RandomSampler_get2D(sampler);
+        Sample3f wi = cosineSampleHemisphere(uv.x, uv.y, sample.Ng);
+        
+        Vec3fa diffuse = Material__eval(material_array, matId, brdf, wo, sample, wi.v);
+
+        Lw *= M_PI * diffuse;
+
+        ray = Ray(sample.P,wi.v,0.1,inf);
+
+    }
+
+    return L;
+}
+
+/* task that renders a single screen tile */
+Vec3fa Application1::renderPixelOrig(float x, float y, const ISPCCamera& camera, RayStats& stats, RandomSampler& sampler) {
     /* radiance accumulator and weight */
     Vec3fa L = Vec3fa(0.0f);
     Vec3fa Lw = Vec3fa(1.0f);
@@ -106,8 +186,8 @@ Vec3fa Application1::renderPixel(float x, float y, const ISPCCamera& camera, Ray
             Material__preprocess(material_array, matId, brdf, wo, sample);
 
             /* sample BRDF at hit point */
-            Sample3f wi1;
-            Material__sample(material_array, matId, brdf, Lw, wo, sample, wi1, RandomSampler_get2D(sampler));
+            // Sample3f wi1;
+            // Material__sample(material_array, matId, brdf, Lw, wo, sample, wi1, RandomSampler_get2D(sampler));
 
             int id = (int)(RandomSampler_get1D(sampler) * data.scene->lights.size());
             if (id == data.scene->lights.size())
diff --git a/Assignments/Assignment1/Application1.h b/Assignments/Assignment1/Application1.h
index 32e8ec3..eddaa5e 100644
--- a/Assignments/Assignment1/Application1.h
+++ b/Assignments/Assignment1/Application1.h
@@ -1,5 +1,6 @@
 #pragma once
 #include "helper.hpp"
+#include "imgui.h"
 
 
 class Application1 : public Application {
@@ -9,8 +10,31 @@ public:
 
 private:
     Vec3fa renderPixel(float x, float y, const ISPCCamera& camera, RayStats& stats, RandomSampler& sampler) override;
+    Vec3fa renderPixelOrig(float x, float y, const ISPCCamera& camera, RayStats& stats, RandomSampler& sampler);
+    Vec3fa renderPixelPathTracer(float x, float y, const ISPCCamera& camera, RayStats& stats, RandomSampler& sampler);
 
     void drawGUI() override {
+        ImGui::ColorEdit3("Color", colorLight);
+        ImGui::InputInt("Ray depth", &ray_depth);
+        if (ray_depth < 1) {
+            ray_depth = 1;
+        }
+
+        const char* items[] = {"Original", "Path Tracer"};
+        ImGui::Combo("Version", &selected, items, 2);
+        
+        const char* scenes[] = {"Cornell", "Veach"};
+        int oldscene = scene;
+        ImGui::Combo("Scenes", &scene, scenes, 2);
+        if (scene != oldscene) {
+            Data_Destructor(&data);
+            Data_Constructor(&data, 1, 8);
+            if (scene == 0)
+                standardScene();
+            if (scene == 1)
+                veachScene();
+        }
+        
     }
 
     void initScene() override;
@@ -20,4 +44,8 @@ private:
     void veachScene();
 
     float colorLight[3] = {1.0f, 1.0f, 1.0f};
+    int ray_depth = 5;
+    int selected = 0;
+    int scene = 0;
+    
 };