Added support for rendering diffuse area lights

README.md

@@ -6,7 +6,9 @@ A simple C++ Raytracer based on "Ray Tracing in One Weekend" book.
 
 ![render image with motion blur](docs/render-motion-blur.png)
 
-![render image with marble textyre](docs/render-marble.png)
+![render image with marble texture](docs/render-marble.png)
+
+![render image with diffuse light](docs/render-light.png)
 
 ## Features
 
@@ -25,6 +27,7 @@ A simple C++ Raytracer based on "Ray Tracing in One Weekend" book.
 * Motion blur.
 * Checked textures.
 * Perlin noise based textures.
+* Diffuse area light.
 
 ## Building
 

src/camera.cpp

@@ -5,29 +5,34 @@
 
 using namespace std;
 
-inline Color background(const Ray& ray) {
+Color Camera::background(const Ray& ray) {
+    /*
     auto unitDir = ray.dir().unit();
     auto a = 0.5 * (unitDir.y() + 1.0);
     return (1.0 - a) * Color(1.0, 1.0, 1.0) + a * Color(0.5, 0.7, 1.0);
+    */
+    return _background;
 }
 
-inline Color color(const Ray& ray, int depth, const shared_ptr<const Intersectable>& intersectable) {
+Color Camera::color(const Ray& ray, int depth, const shared_ptr<const Intersectable>& intersectable) {
     if (depth <= 0) return Color(0.0, 0.0, 0.0);
     Hit hit;
-    if (intersectable->intersects(ray, Interval(0.001), hit)) {
-        Ray scattered;
-        Color attenuation;
-        if (hit.material()->scatter(ray, hit, attenuation, scattered))
-            return attenuation * color(scattered, depth - 1, intersectable);
-        return Color(0,0,0);
-    }
-
-    return background(ray);
+    if (!intersectable->intersects(ray, Interval(0.001), hit)) return background(ray);
+
+    Ray scattered;
+    Color attenuation;
+    Color color_from_emission = hit.material()->emitted(hit.u(), hit.v(), hit.point());
+
+    if (!hit.material()->scatter(ray, hit, attenuation, scattered)) return color_from_emission;
+
+    Color color_from_scatter = attenuation * color(scattered, depth - 1, intersectable);
+
+    return color_from_emission + color_from_scatter;
 }
 
 Camera::Camera(double aspect, int samplesPerPixel,
-       int maxDepth, int imageWidth, double vfov, Vector lookFrom, Vector lookAt, Vector vup, double defocusAngle, double focusDist): _aspect(aspect), _samplesPerPixel(samplesPerPixel), _maxDepth(maxDepth), _lookFrom(lookFrom),
-           _lookAt(lookAt), _vup(vup), _defocusAngle(defocusAngle), _focusDist(focusDist)
+       int maxDepth, int imageWidth, double vfov, Vector lookFrom, Vector lookAt, Vector vup, Color background, double defocusAngle, double focusDist): _aspect(aspect), _samplesPerPixel(samplesPerPixel), _maxDepth(maxDepth), _lookFrom(lookFrom),
+           _lookAt(lookAt), _vup(vup), _background(background), _defocusAngle(defocusAngle), _focusDist(focusDist)
 {
     auto imageHeight = int(imageWidth / aspect);
     imageHeight = (imageHeight < 1) ? 1 : imageHeight;

src/camera.h

@@ -35,6 +35,8 @@ class Camera {
     Vector _defocusDiskU;
     Vector _defocusDiskV;
 
+    Color _background;
+
     Point defocusDiskSample() {
         auto p = Vector::randomInUnitDisc();
         return _lookFrom + (p.x() * _defocusDiskU) + (p.y() * _defocusDiskV);
@@ -50,12 +52,15 @@ class Camera {
            Vector lookFrom = Vector(13.0, 2.0, 3.0),
            Vector lookAt = Vector(0.0, 0.0, 0.0),
            Vector vup = Vector(0.0, 1.0, 0.0),
+           Color background = Color(0.7, 0.8, 1.0),
            double defocusAngle = 0.6,
            double focusDist = 10.0);
 
     double aspect() const { return _aspect; }
     const Viewport& viewport() const { return _viewport; }
 
+    Color color(const Ray& ray, int depth, const std::shared_ptr<const Intersectable>& intersectable);
+    Color background(const Ray& ray);
     void render(const std::shared_ptr<const Intersectable>& intersectable, const std::string& filename);
 
 };

src/main.cpp

@@ -67,7 +67,7 @@ void twoSpheres() {
     scene->add(make_shared<Sphere>(Point(0.0, -10.0, 0.0), 10.0, make_shared<Lambertian>(checker)));
     scene->add(make_shared<Sphere>(Point(0.0, 10.0, 0.0), 10.0, make_shared<Lambertian>(checker)));
 
-    Camera camera(16.0 / 9.0, 50, 50, 400, 20.0, Vector(13.0, 2.0, 3.0), Vector(0.0, 0.0, 0.0), Vector(0.0, 1.0, 0.0), 0.0, 10.0);
+    Camera camera(16.0 / 9.0, 50, 50, 400, 20.0, Vector(13.0, 2.0, 3.0), Vector(0.0, 0.0, 0.0), Vector(0.0, 1.0, 0.0), Color(0.7, 0.8, 1.0), 0.0, 10.0);
 
     camera.render(scene, "image.ppm");
 }
@@ -80,7 +80,7 @@ void earth() {
     shared_ptr<Scene> scene = make_shared<Scene>();
     scene->add(globe);
 
-    Camera camera(16.0 / 9.0, 100, 50, 400, 20.0, Vector(0.0, 0.0, 12.0), Vector(0.0, 0.0, 0.0), Vector(0.0, 1.0, 0.0), 0.0, 10.0);
+    Camera camera(16.0 / 9.0, 100, 50, 400, 20.0, Vector(0.0, 0.0, 12.0), Vector(0.0, 0.0, 0.0), Vector(0.0, 1.0, 0.0), Color(0.7, 0.8, 1.0), 0.0, 10.0);
 
     camera.render(scene, "image.ppm");
 }
@@ -113,18 +113,34 @@ void quads() {
     scene->add(make_shared<Quad>(Point(-2, 3, 1), Vector(4, 0, 0), Vector(0, 0, 4), upper_orange));
     scene->add(make_shared<Quad>(Point(-2,-3, 5), Vector(4, 0, 0), Vector(0, 0,-4), lower_teal));
 
-    Camera camera(1.0, 100, 50, 400, 80.0, Vector(0, 0, 9), Vector(0, 0, 0), Vector(0.0, 1.0, 0.0), 0.0);
+    Camera camera(1.0, 100, 50, 400, 80.0, Vector(0, 0, 9), Vector(0, 0, 0), Vector(0.0, 1.0, 0.0), Color(0.7, 0.8, 1.0), 0.0);
+
+    camera.render(scene, "image.png");
+}
+
+void simple_light() {
+    shared_ptr<Scene> scene = make_shared<Scene>();
+
+    auto pertext = make_shared<NoiseTexture>(4);
+    scene->add(make_shared<Sphere>(Point(0.0, -1000.0, 0.0), 1000.0, make_shared<Lambertian>(pertext)));
+    scene->add(make_shared<Sphere>(Point(0.0, 2.0, 0.0), 2.0, make_shared<Lambertian>(pertext)));
+
+    auto difflight = make_shared<DiffuseLight>(Color(4.0, 4.0, 4.0));
+    scene->add(make_shared<Quad>(Point(3.0, 1.0, -2.0), Vector(2.0, 0.0, 0.0), Vector(0.0, 2.0, 0.0), difflight));
+
+    Camera camera(16.0 / 9.0, 500, 50, 1920, 20.0, Vector(26.0, 3.0, 6.0), Vector(0.0, 2.0, 0.0), Vector(0.0, 1.0, 0.0), Color(0.0, 0.0, 0.0), 0.0);
 
     camera.render(scene, "image.png");
 }
 
 int main() {
-    switch (5) {
+    switch (6) {
         case 1: randomSpheres(); break;
         case 2: twoSpheres(); break;
         case 3: earth(); break;
         case 4: twoPerlinSpheres(); break;
         case 5: quads(); break;
+        case 6: simple_light(); break;
     }
     return 0;
 }

src/material.h

@@ -9,6 +9,9 @@ class Material {
 
     virtual ~Material() = default;
     virtual bool scatter(const Ray& ray, const Hit& hit, Color& attenuation, Ray& scattered) const = 0;
+    virtual Color emitted(double u, double v, const Point& point) const {
+        return Color(0.0, 0.0, 0.0);
+    }
 
 };
 
@@ -89,3 +92,24 @@ class Dielectric : public Material {
     }
 
 };
+
+class DiffuseLight : public Material {
+
+private:
+
+    std::shared_ptr<Texture> _texture;
+
+public:
+
+    DiffuseLight(const std::shared_ptr<Texture>& texture):_texture(texture) {}
+    DiffuseLight(const Color& color):_texture(std::make_shared<SolidColor>(color)) {}
+
+    bool scatter(const Ray &ray, const Hit &hit, Color &attenuation, Ray &scattered) const override {
+        return false;
+    }
+
+    Color emitted(double u, double v, const Point &point) const override {
+        return _texture->color(u, v, point);
+    }
+
+};