translate ray tracer code

assets/trace.wgsl

@@ -5,70 +5,213 @@
 
 @group(0) @binding(2) var<uniform> config: TracerUniforms;
 
+@group(0) @binding(3) var<uniform> view: ViewUniform;
+
+struct View {
+    view_proj: mat4x4<f32>,
+    view: mat4x4<f32>,
+    projection: mat4x4<f32>,
+    inv_view_proj: mat4x4<f32>,
+    inv_view: mat4x4<f32>, // equiv to Unity's _CameraToWorld
+    inv_projection: mat4x4<f32>, // equic to Unity's _CameraInverseProjection
+};
+
+struct ViewUniform {
+    clip_from_world: mat4x4<f32>,
+    unjittered_clip_from_world: mat4x4<f32>,
+    world_from_clip: mat4x4<f32>,
+    world_from_view: mat4x4<f32>,
+    view_from_world: mat4x4<f32>,
+    clip_from_view: mat4x4<f32>,
+    view_from_clip: mat4x4<f32>,
+    world_position: vec3<f32>,
+    exposure: f32,
+    viewport: vec4<f32>,
+    frustum: array<vec4<f32>, 6>,
+    color_grading: vec4<f32>, // simplified for example
+    mip_bias: f32,
+    frame_count: u32,
+};
+
 struct TracerUniforms {
     sky_color: vec4<f32>,
 }
 
-fn hash(value: u32) -> u32 {
-    var state = value;
-    state = state ^ 2747636419u;
-    state = state * 2654435769u;
-    state = state ^ (state >> 16u);
-    state = state * 2654435769u;
-    state = state ^ (state >> 16u);
-    state = state * 2654435769u;
-    return state;
-}
-
-fn randomFloat(value: u32) -> f32 {
-    return f32(hash(value)) / 4294967295.0;
-}
-
 @compute @workgroup_size(8, 8, 1)
 fn init(@builtin(global_invocation_id) invocation_id: vec3<u32>, @builtin(num_workgroups) num_workgroups: vec3<u32>) {
     let location = vec2<i32>(i32(invocation_id.x), i32(invocation_id.y));
 
-    let randomNumber = randomFloat((invocation_id.y << 16u) | invocation_id.x);
+    let color = vec4(0.0);
-    let alive = randomNumber > 0.9;
-    // Use alpha channel to keep track of cell's state
-    let color = vec4(config.sky_color.rgb, f32(alive));
 
     textureStore(output, location, color);
 }
 
-fn is_alive(location: vec2<i32>, offset_x: i32, offset_y: i32) -> i32 {
-    let value: vec4<f32> = textureLoad(input, location + vec2<i32>(offset_x, offset_y));
-    return i32(value.a);
-}
 
-fn count_alive(location: vec2<i32>) -> i32 {
-    return is_alive(location, -1, -1) +
-           is_alive(location, -1,  0) +
-           is_alive(location, -1,  1) +
-           is_alive(location,  0, -1) +
-           is_alive(location,  0,  1) +
-           is_alive(location,  1, -1) +
-           is_alive(location,  1,  0) +
-           is_alive(location,  1,  1);
-}
 
 @compute @workgroup_size(8, 8, 1)
 fn update(@builtin(global_invocation_id) invocation_id: vec3<u32>) {
-let location = vec2<i32>(i32(invocation_id.x), i32(invocation_id.y));
+	let size = textureDimensions(output);
 
-    let n_alive = count_alive(location);
+	let loc = vec2<f32>(f32(invocation_id.x), f32(invocation_id.y)) / vec2<f32>(size.xy);
+	let ndc  = loc * 2.0f - 1.0f;
 
-    var alive: bool;
+    var ray = createCameraRay(ndc);
 
-    if (n_alive == 3) {
+    var result = vec3<f32>(0.0f);
-        alive = true;
-    } else if (n_alive == 2) {
-        let currently_alive = is_alive(location, 0, 0);
-        alive = bool(currently_alive);
-    } else {
-        alive = false;
-    }
-    let color = vec4(config.sky_color.rgb , f32(alive));
 
+    var hit = trace(ray);
+    result += ray.energy * shade(&ray, hit);
+
+    let color = vec4(result , 1.0);
+    let location = vec2<i32>(i32(invocation_id.x), i32(invocation_id.y));
     textureStore(output, location, color);
 }
+
+
+struct Ray {
+    origin: vec3<f32>,
+    direction: vec3<f32>,
+    energy: vec3<f32>,
+}
+
+
+struct RayHit {
+	distance: f32,
+	position: vec3<f32>,
+	normal: vec3<f32>,
+	albedo: vec3<f32>,
+	specular: vec3<f32>
+}
+
+struct Sphere
+{
+	position: vec3<f32>,
+	radius: f32,
+	albedo: vec3<f32>,
+	specular: vec3<f32>
+}
+
+fn createRayHit() -> RayHit {
+    var hit: RayHit;
+    hit.position = vec3<f32>(0.0, 0.0, 0.0);
+    hit.distance = -1.0f; // A negative number to represent infinity
+    hit.normal = vec3<f32>(0.0, 0.0, 0.0);
+    hit.albedo = vec3<f32>(0.0, 0.0, 0.0);
+    hit.specular = vec3<f32>(0.0, 0.0, 0.0);
+    return hit;
+}
+
+
+fn createRay(origin: vec3<f32>, direction: vec3<f32>) -> Ray
+{
+	var ray: Ray;
+	ray.origin = origin;
+	ray.direction = direction;
+	ray.energy = vec3<f32>(1.0f, 1.0f, 1.0f);
+	return ray;
+}
+
+
+fn createCameraRay(ndc: vec2<f32>) -> Ray {
+    // let origin = (view.inv_view * vec4<f32>(0.0, 0.0, 0.0, 1.0)).xyz;
+
+    // let direction_view = (view.inv_projection * vec4<f32>(uv, 0.0, 1.0)).xyz;
+    // let direction = (view.inv_view * vec4<f32>(direction_view, 0.0)).xyz;
+
+    let origin = view.world_position;
+    let target_point = view.world_from_clip * vec4<f32>(ndc, 0.0f, 1.0f);
+    let direction_point = target_point.xyz / target_point.w;
+    let direction = normalize(direction_point - origin);
+
+    return createRay(origin, direction);
+}
+
+fn createSphere(position: vec3<f32>, radius: f32) -> Sphere
+{
+	var s: Sphere;
+	s.position = position;
+	s.radius = radius;
+	s.albedo = vec3<f32>(0.8f, 0.8f, 0.8f);
+	s.specular = vec3<f32>(0.6f, 0.6f, 0.6f);
+	return s;
+}
+
+fn intersectSphere(ray: Ray, bestHit: ptr<function, RayHit>, sphereIndex: u32)
+{
+	//Sphere sphere = _Spheres[sphereIndex];
+	var sphere = createSphere(vec3<f32>(0.0), 1.0f);
+	var d = ray.origin - sphere.position;
+	var p1 = -dot(ray.direction, d);
+	var p2sqr = p1 * p1 - dot(d, d) + sphere.radius * sphere.radius;
+	if p2sqr < 0 {
+		return;
+	}
+	var p2 = sqrt(p2sqr);
+	// var t = p1 - p2 > 0 ? p1 - p2 : p1 + p2;
+	var t = 0f;
+	if p1 - p2 > 0 {
+		t = p1 - p2;
+	} else {
+		t = p1 + p2;
+	}
+	if t > 0 && t < (*bestHit).distance
+	{
+		(*bestHit).position = ray.origin + t * ray.direction;
+		(*bestHit).normal = normalize((*bestHit).position - sphere.position);
+		(*bestHit).albedo = sphere.albedo;
+		(*bestHit).specular = sphere.specular;
+		(*bestHit).distance = t;
+	}
+}
+
+fn intersectGroundPlane(ray: Ray, bestHit: ptr<function,RayHit>)
+{
+	var t = -ray.origin.y / ray.direction.y;
+	if t > 0 && t < (*bestHit).distance
+	{
+		(*bestHit).distance = t;
+		(*bestHit).position = ray.origin + t * ray.direction;
+		(*bestHit).normal = vec3<f32>(0.0f, 1.0f, 0.0f);
+		(*bestHit).albedo = vec3(0.8f);
+		(*bestHit).specular = vec3(0.3f);
+	}
+}
+
+fn trace(ray: Ray) -> RayHit
+{
+	var bestHit = createRayHit();
+	intersectGroundPlane(ray, &bestHit);
+	intersectSphere(ray, &bestHit, 0);
+	return bestHit;
+}
+
+
+fn shade(ray: ptr<function, Ray>, hit: RayHit) -> vec3<f32>
+{
+	if hit.distance > -1.0f
+	{
+		(*ray).origin = hit.position + hit.normal * 0.001f;
+		(*ray).direction = reflect((*ray).direction, hit.normal);
+		(*ray).energy *= hit.specular;
+
+		//Shadows
+		// var shadow = false;
+		// Ray shadowRay = createRay(hit.position + hit.normal * 0.001f, -1 * _DirectionalLight.xyz);
+		// RayHit shadowHit = Trace(shadowRay);
+		// if (shadowHit.distance != 1.#INF)
+		// {
+		// 	return float3(0.0f, 0.0f, 0.0f);
+		// }
+
+		// return saturate(dot(hit.normal, _DirectionalLight.xyz) * -1) * _DirectionalLight.w * hit.albedo;
+		return hit.albedo;
+	}
+	else
+	{
+		(*ray).energy = vec3(0.0f);
+		return vec3<f32>(0.1f);
+		// var theta = acos(ray.direction.y) / -PI;
+		// var phi = atan2(ray.direction.x, -ray.direction.z) / -PI * .5f;
+		// return _SkyboxTexture.SampleLevel(sampler_SkyboxTexture, float2(phi, theta), 0).xyz;
+	}
+}

src/render/pipeline.rs

@@ -15,6 +15,7 @@ use bevy::{
 		},
 		renderer::{RenderDevice, RenderQueue},
 		texture::GpuImage,
+		view::{ViewUniform, ViewUniforms},
 	},
 };
 
@@ -85,6 +86,7 @@ impl FromWorld for TracerPipeline {
 					texture_storage_2d(TextureFormat::Rgba32Float, StorageTextureAccess::ReadOnly),
 					texture_storage_2d(TextureFormat::Rgba32Float, StorageTextureAccess::WriteOnly),
 					uniform_buffer::<TracerUniforms>(false),
+					uniform_buffer::<ViewUniform>(false),
 				),
 			),
 		);
@@ -133,6 +135,7 @@ fn init_pipeline(
 				texture_storage_2d(TextureFormat::Rgba32Float, StorageTextureAccess::ReadOnly),
 				texture_storage_2d(TextureFormat::Rgba32Float, StorageTextureAccess::WriteOnly),
 				uniform_buffer::<TracerUniforms>(false),
+				uniform_buffer::<ViewUniform>(false),
 			),
 		),
 	);
@@ -175,10 +178,13 @@ fn prepare_bind_groups(
 	tracer_uniforms: Res<TracerUniforms>,
 	render_device: Res<RenderDevice>,
 	queue: Res<RenderQueue>,
+	view_uniforms: Res<ViewUniforms>,
 ) {
 	let view_a = gpu_images.get(&tracer_images.0).unwrap();
 	let view_b = gpu_images.get(&tracer_images.1).unwrap();
 
+	//Todo: Insert View Uniforms
+
 	// Uniform buffer is used here to demonstrate how to set up a uniform in a compute shader
 	// Alternatives such as storage buffers or push constants may be more suitable for your use case
 	let mut uniform_buffer = UniformBuffer::from(tracer_uniforms.into_inner());