Ray-caster: map output into sRGB space

Change the base color and default opacity to keep the picture looking
broadly the same.

app-proto/inversive-display/src/main.rs

@@ -72,7 +72,7 @@ fn main() {
     sycamore::render(|| {
         let ctrl_x = create_signal(0.0);
         let ctrl_y = create_signal(0.0);
-        let opacity = create_signal(0.6);
+        let opacity = create_signal(0.5);
         let layer_threshold = create_signal(0.0);
         let display = create_node_ref();
         
@@ -123,6 +123,33 @@ fn main() {
                 const float focal_slope = 0.3;
                 const vec3 light_dir = normalize(vec3(2., 2., 1.));
                 
+                // --- sRGB ---
+                
+                // map colors from RGB space to sRGB space, as specified in the
+                // sRGB standard (IEC 61966-2-1:1999)
+                //
+                //   https://www.color.org/sRGB.pdf
+                //   https://www.color.org/chardata/rgb/srgb.xalter
+                //
+                // in RGB space, color value is proportional to light intensity,
+                // so linear color-vector interpolation corresponds to physical
+                // light mixing. in sRGB space, the color encoding used by many
+                // monitors, we use more of the value interval to represent low
+                // intensities, and less of the interval to represent high
+                // intensities. this improves color quantization
+                
+                float sRGB(float t) {
+                    if (t <= 0.0031308) {
+                        return 12.92*t;
+                    } else {
+                        return 1.055*pow(t, 5./12.) - 0.055;
+                    }
+                }
+                
+                vec3 sRGB(vec3 color) {
+                    return vec3(sRGB(color.r), sRGB(color.g), sRGB(color.b));
+                }
+                
                 // --- inversive geometry ---
                 
                 struct vecInv {
@@ -203,8 +230,8 @@ fn main() {
                     // initialize two spheres
                     vecInv v0 = sphere(vec3(0.5, 0.5, -5. + ctrl.x), 1.);
                     vecInv v1 = sphere(vec3(-0.5, -0.5, -5. + ctrl.y), 1.);
-                    vec3 color0 = vec3(1.0, 0.5, 0.0);
-                    vec3 color1 = vec3(0.0, 0.5, 1.0);
+                    vec3 color0 = vec3(1., 0.214, 0.);
+                    vec3 color1 = vec3(0., 0.214, 1.);
                     
                     // cast rays through the spheres
                     vec2 u0 = sphere_cast(v0, dir);
@@ -236,7 +263,7 @@ fn main() {
                             color = mix(color, frag_color.rgb, frag_color.a);
                         }
                     }
-                    outColor = vec4(color, 1.);
+                    outColor = vec4(sRGB(color), 1.);
                 }
                 "##,
             );