Data passes from vertex to fragment shaders as inter-stage variables declared with @location attributes, automatically interpolated across triangles

Values computed in a vertex shader can be passed to the fragment shader as inter-stage (interpolated) variables. The vertex shader returns a struct with both @builtin(position) and additional @location(n) fields. The GPU interpolates these values across the triangle’s surface — values at corners are smoothly blended at interior pixels. The fragment shader receives them as @location(n) inputs (or by reusing the vertex output struct as its input type). This is how cell coordinates, normals, UVs, and colors travel through the pipeline.

Examples

struct VertexOutput {
  @builtin(position) pos: vec4f,
  @location(0) cell: vec2f,
};
@fragment
fn fragmentMain(input: VertexOutput) -> @location(0) vec4f {
  return vec4f(input.cell / grid, 0, 1);
}

Assessment

Three triangle vertices have @location(0) values 0.0, 0.5, 1.0. What value does the fragment shader receive at the pixel exactly halfway between the 0.5 and 1.0 corners?