bindVertexStage method

@override void bindVertexStage(RenderPass pass, Shader vertexShader, TransientWriter transientsBuffer)

Binds this material's vertex-stage uniforms to vertexShader, called by the encoder only when it used a material-supplied vertex shader (see materialVertexShader). The base implementation is a no-op; a material with vertex-stage parameters binds them here.

Implementation

@override
void bindVertexStage(
  gpu.RenderPass pass,
  gpu.Shader vertexShader,
  TransientWriter transientsBuffer,
) {
  // The generated vertex variant declares the same MaterialParams block as
  // the fragment shader, so a parameter reads the same value in both stages.
  // The variant's keep-alive references the block (see
  // MATERIAL_PARAMS_KEEP_ALIVE in the emitter) so it survives compilation
  // even when Vertex() reads no parameter; binding an optimized-out block
  // crashes the Metal backend.
  parameters.bindUniformBlock(pass, vertexShader, transientsBuffer);
  // Bind the keep-alive block (name must match kVertexKeepAliveBlock in the
  // emitter) to zero: the generated shader multiplies the mesh inputs by it
  // so the optimizer cannot strip a declared attribute when a Vertex() hook
  // replaces the outputs, and zero makes it invisible.
  pass.bindUniform(
    vertexShader.getUniformSlot('VertexKeepAlive'),
    transientsBuffer.emplace(_zeroKeepAlive),
  );
}