Added doc writing dev container.

.devcontainer/devcontainer.json

@@ -0,0 +1,5 @@
+{
+	"name": "Docs DevContainer",
+	"image": "mcr.microsoft.com/devcontainers/javascript-node:1-20-bullseye",
+	"postCreateCommand": "npm install retypeapp --global"
+}

assets/shaders/visibility/material_count.glsl

@@ -1,5 +1,6 @@
+layout(local_size_x=1) in;
 void main() {
-	uint material_index = pixel;
+	uint material_index = gl_GlobalInvocationID.x;
 
 	material_count[material_index] += 1;
 }

docs/Design/Render Models/Visibility/readme.md

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+Visibility buffer rendering is a technique to speed up rendering of scenes with high resolution and high material complexities.
+
+The steps to render a frame are like this:
+1. **Visibility Pass:** First all objects in the scene are rendered to a render target where their material id is recorded.
+2. **Material Count Pass:** Then a compute shader is dispatched to count how many pixels each material covers.
+3. **Material Sum Pass:** Using that count, a prefix sum is performed.
+4. **Pixel Mapping Pass:** The `material_id` target is visited again to store the coordinates of evey pixel of every material.
+5. **Material Evaluation Pass:** Finally a batch of compute shaders is dispatched to evaluate each of the pixels' surface.
+
+```mermaid
+graph LR
+	Visibility --> MaterialCount --> MaterialSum --> PixelMapping --> MaterialEvaluation
+
+	Visibility -- writes to --- material_id[(material_id)]
+	material_id[(material_id)] -- feeds --- MaterialCount
+	MaterialCount -- writes to --- material_count[(material_count)]
+	material_count[(material_count)] -- feeds --- MaterialSum
+	MaterialSum -- writes to --- material_sum[(material_sum)]
+	material_id[(material_id)] -- feeds --- PixelMapping
+	material_sum[(material_sum)] -- feeds --- PixelMapping
+	PixelMapping -- writes to --- material_xy[(material_xy)]
+	material_xy[(material_xy)] -- feeds --- MaterialEvaluation
+```
+---
+## Render Passes
+### Visibility Pass
+Every object in the scene is drawn using a fragment shader which writes their material id to the `material_id` render target.
+Said shader would look something like this.
+```glsl
+// Fragment shader
+layout(location=0) out uint material_id;
+void main() {
+	material_id = material.id;
+}
+```
+Meanwhile the vertex situation is more complicated. If the object has a trivial vertex transform, that is, the final vertex position is the result of the multiplication of it's position matrix by the camera view matrix and the projection matrix, then it is evaluated instantly at the moment of rendering, with no extra pre-processing.
+
+But if the material performs a non-trivial transformation such as mesh skinning or vertex animation, then the engine has to convert that vertex shader to a compute shader and evalute that every frame and write it's result to a buffer where then the trivial vertex shader would read from and render as usual.
+
+### Material Count Pass
+Once the `material_id` render target is populated with the visible surfaces/materials the material count pass is executed to determine how many pixels of each material there is. This is done to be able to schedule the indirect material evaluation shaders.
+
+This pass consists of a single common compute shader that visit every pixel and increments a counter for each material for every pixel that contains it.
+
+```glsl
+// Compute shader
+layout(location=0, binding=0) Texture2D material_id;
+layout(location=0, binding=1) uint[] material_count;
+layout(local_size_x=32, local_size_x=32) in;
+void main() {
+	material_count[material_id] += 1;
+}
+```
+
+### Material Sum Pass
+
+```glsl
+// Compute shader
+layout(location=0, binding=0) uint[] material_count;
+layout(location=0, binding=1) uint[] material_sum;
+layout(local_size_x=32) in;
+void main() {
+	uint sum = 0;
+	for (int i = 0; i < n_of_materials; ++i) {
+		material_sum[i] = sum;
+		sum += material_count[i];
+	}
+}
+```
+
+### Pixel Mapping Pass
+Here the `material_id` render target is visited once again, but this time accompanied by the `material_sum` buffer as to build another buffer containing the X and Y coordinates of every pixel of every material.
+
+### Material Evaluation Pass
+Finally this pass performs the evaluation of the user defined materials to perform the actual shading.
+As this pass is performed by dispatching compute shaders that evaluate every pixel each material covers it requires that engine generate a compute shader equivalent of the user defined surface shaders.
+
+Said mapping would look somethis like this.
+```hlsl
+// BESL surface shader
+main: fn () -> void {
+	albedo = material.albedo[uv];
+}
+
+// GLSL compute shader
+void main() {
+	albedo[global_thread_id] = materials[material_id[global_thread_id]].albedo[calculate_uvs()];
+}
+```