Fix color conversion for textures

The textures were appearing washed out in all the renders, which turned
out to be because of the gamma correction we do. So we do the inverse
when converting texture values to Color. This is pretty rudimentary, but
works for now.

Also fixed the staircase scene to use the correct texture for the
stairs.

objs/staircase/staircase.mtl

@@ -221,18 +221,18 @@ newmtl Wood_-_Chair
 Ns 250.0
 Ka 1.0 1.0 1.0
 Kd 0.8 0.3 0.1
-Ks 0.5 0.5 0.5
+Ks 1.0 1.0 1.0
 Ke 0.0 0.0 0.0
 Ni 1.0
 d 1.0
 map_Kd textures/WoodChair.jpg
 illum 2
 
 newmtl Wood_-_Floor
-Ns 250.0
+Ns 1000.0
 Ka 1.0 1.0 1.0
 Kd 0.8 0.3 0.1
-Ks 0.5 0.5 0.5
+Ks 1.0 1.0 1.0
 Ke 0.0 0.0 0.0
 Ni 1.0
 d 1.0
@@ -243,22 +243,22 @@ newmtl Wood_-_Lamp
 Ns 250.0
 Ka 1.0 1.0 1.0
 Kd 0.6 0.4 0.1
-Ks 0.5 0.5 0.5
+Ks 1.0 1.0 1.0
 Ke 0.0 0.0 0.0
 Ni 1.0
 d 1.0
-map_Kd textures/WoodPanel.jpg
+map_Kd textures/Wood.jpg
 illum 2
 
 newmtl Wood_-_Stairs
-Ns 250.0
+Ns 1000.0
 Ka 1.0 1.0 1.0
 Kd 0.8 0.3 0.1
-Ks 0.5 0.5 0.5
+Ks 1.0 1.0 1.0
 Ke 0.0 0.0 0.0
 Ni 1.0
 d 1.0
-map_Kd textures/Wood.jpg
+map_Kd textures/WoodPanel.jpg
 illum 2
 
 newmtl copper.001

scenes/museum.cry

@@ -1,13 +1,15 @@
 {
     num_samples: 16,
     camera: Perspective {
-        origin: Point(2, 10, -2),
-        target: Point(0.5, 3, -3),
+        origin: Point(2.5, 8, -9),
+        target: Point(1, 0, -8),
         up: Vector(0, 0, -1),
+        lens_radius: 0.05,
+        focal_distance: 10,
         fov: 60,
         film: {
-            width: 800,
-            height: 600,
+            width: 850,
+            height: 1000,
         }
     },
     lights: [

scenes/mustang.cry

@@ -0,0 +1,29 @@
+{
+    num_samples: 16,
+    camera: Perspective {
+        origin: Point(1, 0.75, -2),
+        target: Point(-0.25, -0.25, 0),
+        up: Vector(0, 1, 0),
+        fov: 45,
+        film: {
+            width: 800,
+            height: 600,
+        }
+    },
+    lights: [
+        Infinite { intensity: Color(0.5, 0.55, 0.6) }
+    ],
+    materials: {
+        fallback: Matte { reflectance: Color(1, 0.9, 0.8), sigma: 0 },
+        ground: Matte { reflectance: Color(0.9, 0.95, 1.0), sigma: 1000 },
+    },
+    shapes: {
+        light: Disk { origin: Point(0, 2, 0), radius: 3, rotate_x: 90 },
+        ground: Disk { origin: Point(0, 0, 0), radius: 2, rotate_x: 90 },
+    },
+    primitives: [
+        Mesh { file_name: 'objs/local/mustang/mustang.obj', fallback_material: 'fallback' },
+        Shape { shape: 'light', emittance: Color(2, 2, 2) },
+        Shape { shape: 'ground', material: 'ground' }
+    ]
+}

scenes/staircase.cry

@@ -4,25 +4,25 @@
         origin: Point(0, 2, -4.92),
         target: Point(0, 2.5, 0),
         up: Vector(0, 1, 0),
-        lens_radius: 0.01,
-        focal_distance: 7,
+        lens_radius: 0.001,
+        focal_distance: 3,
         fov: 35,
         film: {
-            width: 360,
-            height: 640,
+            width: 720,
+            height: 1280,
         }
     },
     lights: [
-        Point { origin: Point(0, 2.25, -4.5), intensity: Color(0.2, 0.2, 0.2) }
+        Point { origin: Point(0, 2.25, -4.5), intensity: Color(0.3, 0.3, 0.3) }
     ],
     materials: {
         default: Matte { reflectance: Color(1, 1, 1), sigma: 0 }
     },
     shapes: {
-        light1: Disk { origin: Point(0, 5.5, 2.5), rotate_x: 60, rotate_y: 0, radius: 2 },
+        light1: Disk { origin: Point(1, 5.5, 2.5), rotate_x: 60, rotate_y: 0, radius: 2 },
     },
     primitives: [
-        Shape { shape: 'light1', emittance: Color(4, 3, 2) },
+        Shape { shape: 'light1', emittance: Color(5, 5, 5) },
 
         // Model from https://blendswap.com/blend/14449. Exported from Blender
         // and tweaked the material file to make the "Emission" material actually

src/bin/craytracer.rs

@@ -115,8 +115,6 @@ fn show_preview<C, F>(
                         g: pixels[3 * offset + 1] as f64,
                         b: pixels[3 * offset + 2] as f64,
                     }
-                    // Gamma correction
-                    .powf(1.0 / 2.2)
                     .to_rgb();
                     preview_buffer[offset] = (r as u32) << 16 | (g as u32) << 8 | b as u32;
                 }
@@ -277,7 +275,7 @@ where
                 |x, y| {
                     info!("Rendering pixel at ({x},{y})");
                     let color = render_pixel(&mut sampler, x, y, scene);
-                    info!("Color = {} {:?}", color, color.powf(1.0 / 2.2).to_rgb());
+                    info!("Color = {} {:?}", color, color.to_rgb());
                 },
                 on_finish,
             );

src/color.rs

@@ -10,6 +10,8 @@ pub struct Color {
     pub b: f64,
 }
 
+const GAMMA: f64 = 2.2;
+
 impl Color {
     pub const BLACK: Color = Color {
         r: 0.0,
@@ -22,25 +24,32 @@ impl Color {
         b: 1.0,
     };
 
-    pub fn from_rgb(r: u8, g: u8, b: u8) -> Color {
-        Color {
-            r: r as f64 / 255.0,
-            g: g as f64 / 255.0,
-            b: b as f64 / 255.0,
-        }
-    }
     pub fn powf(self, pow: f64) -> Color {
         Color {
             r: self.r.powf(pow),
             g: self.g.powf(pow),
             b: self.b.powf(pow),
         }
     }
+
+    // Very naive conversion to/from rgb color space that just applies some
+    // gamma correction. This should be replaced with a proper spectrum
+    // representation that is then converted to rgb values depending on the film
+    // properties.
+    pub fn from_rgb(r: u8, g: u8, b: u8) -> Color {
+        Color {
+            r: r as f64 / 255.0,
+            g: g as f64 / 255.0,
+            b: b as f64 / 255.0,
+        }
+        .powf(GAMMA)
+    }
     pub fn to_rgb(self) -> (u8, u8, u8) {
+        let Color { r, g, b } = self.powf(1.0 / GAMMA);
         (
-            (self.r.clamp(0.0, 1.0) * 255.0) as u8,
-            (self.g.clamp(0.0, 1.0) * 255.0) as u8,
-            (self.b.clamp(0.0, 1.0) * 255.0) as u8,
+            (r.clamp(0.0, 1.0) * 255.0) as u8,
+            (g.clamp(0.0, 1.0) * 255.0) as u8,
+            (b.clamp(0.0, 1.0) * 255.0) as u8,
         )
     }
     pub fn is_black(self) -> bool {