Mix frame ID into the RNG

src/bin/minitracer/main.rs

@@ -52,14 +52,6 @@ fn main() {
 
 	let format = wgpu::TextureFormat::Bgra8UnormSrgb;
 	let mut tracer = Tracer::new(&device, format);
-	tracer.set_params(
-		&queue,
-		trace::Params {
-			max_reflections: 3,
-			min_strength: 0.1,
-			sphere_count: N_SPHERES,
-		},
-	);
 	let sphere_params: Vec<_> = {
 		let mut rng = rand_pcg::Pcg32::new(42, 0);
 		let distr = anim::SphereParamsDistribution::default();
@@ -69,6 +61,7 @@ fn main() {
 
 	let presenter = Presenter::new(&device, format);
 
+	let mut frame = 0;
 	let mut time = 0.0;
 
 	let mut surface_configured = false;
@@ -100,8 +93,18 @@ fn main() {
 						return;
 					}
 					time += 1. / 60.;
+					frame += 1;
 					let spheres: Vec<_> = sphere_params.iter().map(|p| p.to_sphere(time)).collect();
 					let data = TracerData::new(&device, &tracer, &spheres);
+					tracer.set_params(
+						&queue,
+						trace::Params {
+							max_reflections: 3,
+							min_strength: 0.1,
+							sphere_count: N_SPHERES,
+							seed: frame,
+						},
+					);
 
 					let output = surface.get_current_texture().unwrap();
 					let view = output.texture.create_view(&wgpu::TextureViewDescriptor::default());

src/bin/minitracer/trace.rs

@@ -10,6 +10,7 @@ pub struct Params {
 	pub max_reflections: u32,
 	pub min_strength: f32,
 	pub sphere_count: u32,
+	pub seed: u32,
 }
 
 #[derive(Debug, Clone, Copy)]

src/bin/minitracer/trace.wgsl

@@ -2,6 +2,7 @@ struct Params {
 	max_reflections: i32,
 	min_strength: f32,
 	sphere_count: i32,
+	seed: u32,
 }
 
 struct Sphere {
@@ -113,7 +114,7 @@ var<private> rand_state: u32;
 fn seed(key: vec4f) {
 	let x = bitcast<u32>(key.x);
 	let y = bitcast<u32>(key.y);
-	rand_state = hash(hash(x) ^ y);
+	rand_state = hash(hash(hash(params.seed) ^ x) ^ y);
 }
 
 fn rand_next() -> u32 {