Wgpu Shader Specialist

wgpu Shader Specialist

Expert skill for wgpu-based GPU rendering and WGSL shader development.

When to Use

Activate this skill when the user:

• Discusses GPU rendering or graphics
• Writes or debugs WGSL shaders
• Configures render pipelines
• Works with textures or buffers
• Optimizes GPU performance

wgpu Architecture

Core Concepts

Instance → Adapter → Device → Queue
                          ↓
              RenderPipeline ← BindGroupLayout
                          ↓
              CommandEncoder → RenderPass → Submit

FLUI's wgpu Usage

• Backend: wgpu 25.x (stay on 25.x - 26.0+ has issues)
• Features: Vulkan/Metal/DX12/WebGPU
• Text: glyphon for GPU text
• Paths: lyon for tessellation

WGSL Shader Patterns

Vertex Shader

struct VertexInput {
    @location(0) position: vec3<f32>,
    @location(1) tex_coords: vec2<f32>,
}

struct VertexOutput {
    @builtin(position) clip_position: vec4<f32>,
    @location(0) tex_coords: vec2<f32>,
}

@vertex
fn vs_main(in: VertexInput) -> VertexOutput {
    var out: VertexOutput;
    out.clip_position = vec4<f32>(in.position, 1.0);
    out.tex_coords = in.tex_coords;
    return out;
}

Fragment Shader

@group(0) @binding(0)
var t_diffuse: texture_2d<f32>;
@group(0) @binding(1)
var s_diffuse: sampler;

@fragment
fn fs_main(in: VertexOutput) -> @location(0) vec4<f32> {
    return textureSample(t_diffuse, s_diffuse, in.tex_coords);
}

Uniform Buffer

struct Uniforms {
    transform: mat4x4<f32>,
    color: vec4<f32>,
}

@group(0) @binding(0)
var<uniform> uniforms: Uniforms;

Common Patterns

Render Pipeline Creation

let pipeline = device.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
    label: Some("Render Pipeline"),
    layout: Some(&pipeline_layout),
    vertex: wgpu::VertexState {
        module: &shader,
        entry_point: Some("vs_main"),
        buffers: &[vertex_buffer_layout],
        compilation_options: Default::default(),
    },
    fragment: Some(wgpu::FragmentState {
        module: &shader,
        entry_point: Some("fs_main"),
        targets: &[Some(wgpu::ColorTargetState {
            format: surface_format,
            blend: Some(wgpu::BlendState::ALPHA_BLENDING),
            write_mask: wgpu::ColorWrites::ALL,
        })],
        compilation_options: Default::default(),
    }),
    primitive: wgpu::PrimitiveState::default(),
    depth_stencil: None,
    multisample: wgpu::MultisampleState::default(),
    multiview: None,
    cache: None,
});

Buffer Updates

// Staging buffer pattern for frequent updates
queue.write_buffer(&uniform_buffer, 0, bytemuck::bytes_of(&uniforms));

GPU Debugging

Validation Errors

// Enable validation in development
let instance = wgpu::Instance::new(&wgpu::InstanceDescriptor {
    backends: wgpu::Backends::all(),
    flags: wgpu::InstanceFlags::validation(),
    ..Default::default()
});

Performance Tips

1. Batch draw calls: Minimize pipeline switches
2. Instanced rendering: For repeated geometry
3. Texture atlases: Reduce bind group changes
4. Buffer pooling: Reuse buffers instead of recreating

Common Issues

• Validation error: Check bind group compatibility
• Black screen: Verify clip space coordinates (-1 to 1)
• Texture sampling: Check texture format compatibility
• Alignment: WGSL requires 16-byte alignment for uniforms

FLUI-Specific Considerations

Layer Composition

• Use separate render passes for overlay layers
• Implement scissor rects for clipping
• Consider texture caching for complex shapes

Text Rendering

// glyphon integration
let mut text_renderer = TextRenderer::new(
    &device,
    &queue,
    swash_cache,
    Some(surface_format),
);

Performance Monitoring

• Track GPU buffer allocations
• Monitor texture memory usage
• Profile shader execution time