#version 450

// iter3 gl_FragCoord-encoded fragment shader.
// For each pixel at integer position (x, y):
//   R = x / 255    -> byte x   (UNORM)
//   G = y / 255    -> byte y   (UNORM)
//   B = 0x80       -> sentinel proving the frag shader executed
//   A = 0xff       -> opaque
// Readback: pixel at (col, row) should be 0xff80(row)(col) LE.

layout(location = 0) out vec4 outColor;

void main() {
    uvec2 ipos = uvec2(gl_FragCoord.xy);
    outColor = vec4(
        float(ipos.x) / 255.0,
        float(ipos.y) / 255.0,
        128.0 / 255.0,
        1.0
    );
}