Function createPieRenderer

src/renderers/createPieRenderer.ts:150–427

(device: GPUDevice, options?: PieRendererOptions)

]);

export function createPieRenderer(device: GPUDevice, options?: PieRendererOptions): PieRenderer {
  let disposed = false;
  const targetFormat = options?.targetFormat ?? DEFAULT_TARGET_FORMAT;

  const bindGroupLayout = device.createBindGroupLayout({
    entries: [{ binding: 0, visibility: GPUShaderStage.VERTEX, buffer: { type: 'uniform' } }],
  });

  // VSUniforms in `pie.wgsl`: mat4x4 (64) + viewportPx vec2 (8) + pad vec2 (8) = 80 bytes.
  const vsUniformBuffer = createUniformBuffer(device, 80, { label: 'pieRenderer/vsUniforms' });

  // Reused CPU-side staging for uniform writes (avoid per-frame allocations).
  const vsUniformScratchBuffer = new ArrayBuffer(80);
  const vsUniformScratchF32 = new Float32Array(vsUniformScratchBuffer);

  const bindGroup = device.createBindGroup({
    layout: bindGroupLayout,
    entries: [{ binding: 0, resource: { buffer: vsUniformBuffer } }],
  });

  const pipeline = createRenderPipeline(device, {
    label: 'pieRenderer/pipeline',
    bindGroupLayouts: [bindGroupLayout],
    vertex: {
      code: pieWgsl,
      label: 'pie.wgsl',
      buffers: [
        {
          arrayStride: INSTANCE_STRIDE_BYTES,
          stepMode: 'instance',
          attributes: [
            { shaderLocation: 0, format: 'float32x2', offset: 0 }, // center
            { shaderLocation: 1, format: 'float32', offset: 8 }, // startAngleRad
            { shaderLocation: 2, format: 'float32', offset: 12 }, // endAngleRad
            { shaderLocation: 3, format: 'float32x2', offset: 16 }, // radiiPx
            { shaderLocation: 4, format: 'float32x4', offset: 24 }, // color
          ],
        },
      ],
    },
    fragment: {
      code: pieWgsl,
      label: 'pie.wgsl',
      formats: targetFormat,
      // Standard alpha blending for AA edges and translucent slice colors.
      blend: {
        color: { operation: 'add', srcFactor: 'src-alpha', dstFactor: 'one-minus-src-alpha' },
        alpha: { operation: 'add', srcFactor: 'one', dstFactor: 'one-minus-src-alpha' },
      },
    },
    primitive: { topology: 'triangle-list', cullMode: 'none' },
    multisample: { count: 1 },
  });

  let instanceBuffer: GPUBuffer | null = null;
  let instanceCount = 0;
  let cpuInstanceStagingBuffer = new ArrayBuffer(0);
  let cpuInstanceStagingF32 = new Float32Array(cpuInstanceStagingBuffer);