fire color palette

tinykaboom.cpp

@@ -46,6 +46,23 @@ float fractal_brownian_motion(const Vec3f &x) {
     return f/0.9375;
 }
 
+Vec3f palette_fire(const float d) {
+    const Vec3f   yellow(1.7, 1.3, 1.0); // note that the color is "hot", i.e. has components >1
+    const Vec3f   orange(1.0, 0.6, 0.0);
+    const Vec3f      red(1.0, 0.0, 0.0);
+    const Vec3f darkgray(0.2, 0.2, 0.2);
+    const Vec3f     gray(0.4, 0.4, 0.4);
+
+    float x = std::max(0.f, std::min(1.f, d));
+    if (x<.25f)
+        return lerp(gray, darkgray, x*4.f);
+    else if (x<.5f)
+        return lerp(darkgray, red, x*4.f-1.f);
+    else if (x<.75f)
+        return lerp(red, orange, x*4.f-2.f);
+    return lerp(orange, yellow, x*4.f-3.f);
+}
+
 float signed_distance(const Vec3f &p) {
     float displacement = -fractal_brownian_motion(p*3.4)*noise_amplitude;
     return p.norm() - (sphere_radius + displacement);
@@ -86,9 +103,10 @@ int main() {
             float dir_z = -height/(2.*tan(fov/2.));
             Vec3f hit;
             if (sphere_trace(Vec3f(0, 0, 3), Vec3f(dir_x, dir_y, dir_z).normalize(), hit)) { // the camera is placed to (0,0,3) and it looks along the -z axis
+                float noise_level = (sphere_radius-hit.norm())/noise_amplitude;
                 Vec3f light_dir = (Vec3f(10, 10, 10) - hit).normalize();                     // one light is placed to (10,10,10)
                 float light_intensity  = std::max(0.4f, light_dir*distance_field_normal(hit));
-                framebuffer[i+j*width] = Vec3f(1, 1, 1)*light_intensity;
+                framebuffer[i+j*width] = palette_fire((-.2 + noise_level)*2)*light_intensity;
             } else {
                 framebuffer[i+j*width] = Vec3f(0.2, 0.7, 0.8); // background color
             }