Implement DiffuseLight material.

Allow Scenes to define global_illumination so scenes without lighting
can continue to work.

rtiow/src/lib.rs

@@ -8,6 +8,7 @@ pub mod material;
 pub mod moving_sphere;
 pub mod perlin;
 pub mod ray;
+pub mod rect;
 pub mod renderer;
 pub mod scenes;
 pub mod sphere;

rtiow/src/material.rs

@@ -31,6 +31,9 @@ pub struct ScatterResponse {
 
 pub trait Material: Send + Sync {
     fn scatter(&self, r_in: &Ray, rec: &HitRecord) -> ScatterResponse;
+    fn emitted(&self, _u: f32, _v: f32, _p: Vec3) -> Vec3 {
+        Vec3::new(0., 0., 0.)
+    }
 }
 
 pub struct Lambertian {
@@ -149,3 +152,27 @@ impl Material for Dielectric {
         }
     }
 }
+
+pub struct DiffuseLight {
+    emit: Box<Texture>,
+}
+
+impl DiffuseLight {
+    pub fn new(emit: Box<Texture>) -> DiffuseLight {
+        DiffuseLight { emit }
+    }
+}
+
+impl Material for DiffuseLight {
+    fn scatter(&self, _r_in: &Ray, _rec: &HitRecord) -> ScatterResponse {
+        ScatterResponse {
+            scattered: Default::default(),
+            attenutation: Default::default(),
+            reflected: false,
+        }
+    }
+
+    fn emitted(&self, u: f32, v: f32, p: Vec3) -> Vec3 {
+        self.emit.value(u, v, p)
+    }
+}

rtiow/src/rect.rs

@@ -0,0 +1,58 @@
+use aabb::AABB;
+use hitable::Hit;
+use hitable::HitRecord;
+use material::Material;
+use ray::Ray;
+use vec3::Vec3;
+
+pub struct XYRect {
+    x0: f32,
+    x1: f32,
+    y0: f32,
+    y1: f32,
+    k: f32,
+    material: Box<Material>,
+}
+
+impl XYRect {
+    pub fn new(x0: f32, x1: f32, y0: f32, y1: f32, k: f32, material: Box<Material>) -> XYRect {
+        XYRect {
+            x0,
+            x1,
+            y0,
+            y1,
+            k,
+            material,
+        }
+    }
+}
+
+impl Hit for XYRect {
+    fn hit(&self, r: Ray, t_min: f32, t_max: f32) -> Option<HitRecord> {
+        let t = (self.k - r.origin.z) / r.direction.z;
+        if t < t_min || t > t_max {
+            return None;
+        }
+        let x = r.origin.x + t * r.direction.x;
+        let y = r.origin.y + t * r.direction.y;
+        if x < self.x0 || x > self.x1 || y < self.y0 || y > self.y1 {
+            return None;
+        }
+        let u = (x - self.x0) / (self.x1 - self.x0);
+        let v = (y - self.y0) / (self.y1 - self.y0);
+        Some(HitRecord {
+            t,
+            uv: (u, v),
+            p: r.point_at_parameter(t),
+            normal: Vec3::new(0., 0., 1.),
+            material: &*self.material,
+        })
+    }
+
+    fn bounding_box(&self, _t_min: f32, _t_max: f32) -> Option<AABB> {
+        Some(AABB::new(
+            Vec3::new(self.x0, self.y0, self.k - 0.0001),
+            Vec3::new(self.x1, self.y1, self.k + 0.0001),
+        ))
+    }
+}

rtiow/src/renderer.rs

@@ -96,21 +96,36 @@ pub struct Scene {
     pub subsamples: usize,
     pub width: usize,
     pub height: usize,
+    pub global_illumination: bool,
 }
 
-fn color(r: Ray, world: &Hit, depth: usize) -> Vec3 {
+// color will trace ray up to 50 bounces deep accumulating color as it goes.  If
+// global_illumination is true, a default light background color is assumed and will light the
+// world.  If false, it is expected the scene has emissive light sources.
+fn color(r: Ray, world: &Hit, depth: usize, global_illumination: bool) -> Vec3 {
     if let Some(rec) = world.hit(r, 0.001, std::f32::MAX) {
+        let (u, v) = rec.uv;
+        let emitted = rec.material.emitted(u, v, rec.p);
         let scatter_response = rec.material.scatter(&r, &rec);
         if depth < 50 && scatter_response.reflected {
-            return scatter_response.attenutation
-                * color(scatter_response.scattered, world, depth + 1);
+            return emitted + scatter_response.attenutation * color(
+                scatter_response.scattered,
+                world,
+                depth + 1,
+                global_illumination,
+            );
+        } else {
+            return emitted;
         }
-        return Default::default();
     }
+    if global_illumination {
         // No hit, choose color from background.
         let unit_direction = r.direction.unit_vector();
         let t = 0.5 * (unit_direction.y + 1.);
-    Vec3::new(1., 1., 1.) * (1. - t) + Vec3::new(0.5, 0.7, 1.) * t
+        return Vec3::new(1., 1., 1.) * (1. - t) + Vec3::new(0.5, 0.7, 1.) * t;
+    }
+    // No global illumination, so background is black.
+    Vec3::new(0., 0., 0.)
 }
 
 fn trace_pixel(x: usize, y: usize, scene: &Scene) -> Vec3 {
@@ -118,7 +133,7 @@ fn trace_pixel(x: usize, y: usize, scene: &Scene) -> Vec3 {
     let u = (rng.gen_range::<f32>(0., 1.) + x as f32) / scene.width as f32;
     let v = (rng.gen_range::<f32>(0., 1.) + y as f32) / scene.height as f32;
     let ray = scene.camera.get_ray(u, v);
-    color(ray, scene.world.as_ref(), 0)
+    color(ray, scene.world.as_ref(), 0, scene.global_illumination)
 }
 
 fn render_worker(

rtiow/src/scenes/bench.rs

@@ -73,5 +73,6 @@ pub fn new(opt: &Opt) -> Scene {
         subsamples: opt.subsamples,
         width: opt.width,
         height: opt.height,
+        global_illumination: true,
     }
 }

rtiow/src/scenes/book.rs

@@ -50,6 +50,7 @@ pub fn new(opt: &Opt) -> Scene {
         subsamples: opt.subsamples,
         width: opt.width,
         height: opt.height,
+        global_illumination: true,
     }
 }
 

rtiow/src/scenes/bvh.rs

@@ -71,5 +71,6 @@ pub fn new(opt: &Opt) -> Scene {
         subsamples: opt.subsamples,
         width: opt.width,
         height: opt.height,
+        global_illumination: true,
     }
 }

rtiow/src/scenes/test.rs

@@ -4,7 +4,9 @@ use camera::Camera;
 use hitable::Hit;
 use hitable_list::HitableList;
 use kdtree::KDTree;
+use material::DiffuseLight;
 use material::Lambertian;
+use rect::XYRect;
 use renderer::Opt;
 use renderer::Scene;
 use sphere::Sphere;
@@ -14,7 +16,7 @@ use texture::NoiseTexture;
 use vec3::Vec3;
 
 pub fn new(opt: &Opt) -> Scene {
-    let lookfrom = Vec3::new(0., 5., 20.);
+    let lookfrom = Vec3::new(30., 2., 0.);
     let lookat = Vec3::new(0., 1., 0.);
     let dist_to_focus = 10.0;
     let aperture = 0.0;
@@ -53,6 +55,26 @@ pub fn new(opt: &Opt) -> Scene {
             // Box::new(Lambertian::new(ground_color)),
             Box::new(Lambertian::new(Box::new(NoiseTexture::with_scale(10.)))),
         )),
+        Box::new(XYRect::new(
+            0.,
+            4.,
+            0.,
+            4.,
+            -4.,
+            Box::new(DiffuseLight::new(Box::new(ConstantTexture::new(
+                Vec3::new(4., 4., 4.),
+            )))),
+        )),
+        Box::new(XYRect::new(
+            0.,
+            4.,
+            0.,
+            4.,
+            4.,
+            Box::new(DiffuseLight::new(Box::new(ConstantTexture::new(
+                Vec3::new(0., 4., 4.),
+            )))),
+        )),
         /*
         Box::new(Sphere::new(
             Vec3::new(0., 0., 0.),
@@ -90,5 +112,6 @@ pub fn new(opt: &Opt) -> Scene {
         subsamples: opt.subsamples,
         width: opt.width,
         height: opt.height,
+        global_illumination: false,
     }
 }

rtiow/src/scenes/tutorial.rs

@@ -76,5 +76,6 @@ pub fn new(opt: &Opt) -> Scene {
         subsamples: opt.subsamples,
         width: opt.width,
         height: opt.height,
+        global_illumination: true,
     }
 }

rtiow/src/texture.rs

@@ -1,7 +1,6 @@
 use image::RgbImage;
 
 use perlin::turb;
-use perlin::GENERATOR;
 use vec3::Vec3;
 
 pub trait Texture: Send + Sync {