Constant SIMPLE_FRAGMENT_SHADER 

pub const SIMPLE_FRAGMENT_SHADER: &str = r#"
struct VertexOutput {
    @builtin(position) clip_position: vec4<f32>,
    @location(0) color: vec4<f32>,
}

@fragment
fn fs_main(in: VertexOutput) -> @location(0) vec4<f32> {
    return in.color;
}
"#;

Simple fragment shader (currently used, solid color output)

Pipeline Stage 3: FRAGMENT/PIXEL PROCESSING

• Runs once for each pixel that the point covers
• Receives interpolated color from vertex shader
• Returns color directly (no modifications)

For a scatter plot with 1 million points, this shader may run 1-4 million times per frame (depending on point sizes).

GPU runs these in parallel, which is why we can render so fast!