assert.wgsl

fn isfinite(x: f32) -> bool {
    return clamp(x, -3.4e38, 3.4e38) == x;
}

fn hash12(p: float2) -> float {
    var p3  = fract(float3(p.xyx) * .1031);
    p3 += dot(p3, p3.yzx + 33.33);
    return fract((p3.x + p3.y) * p3.z);
}

@stage(compute) @workgroup_size(16, 16)
fn main_image(@builtin(global_invocation_id) id: uint3) {
    // Viewport resolution (in pixels)
    let screen_size = uint2(textureDimensions(screen));

    // Prevent overdraw for workgroups on the edge of the viewport
    if (id.x >= screen_size.x || id.y >= screen_size.y) { return; }

    // Pixel coordinates (centre of pixel, origin at bottom left)
    let fragCoord = float2(float(id.x) + .5, float(screen_size.y - id.y) - .5);

    // Normalised pixel coordinates (from 0 to 1)
    let uv = fragCoord / float2(screen_size);

    // Time varying pixel colour
    var col = .5 + .5 * cos(time.elapsed + uv.xyxx + float4(0.,2.,4.,0.));

    col.x /= floor(3. * hash12(fragCoord));
    col.z -= hash12(fragCoord);
    col.z = log(col.z);
    if (time.frame % 199u == 0u) { col.w = col.x; }

    assert(0, isfinite(col.x)); // inf
    assert(1, isfinite(col.y));
    assert(2, isfinite(col.z)); // nan
    assert(3, isfinite(col.w)); // rare

    // Output to screen (linear colour space)
    textureStore(screen, int2(id.xy), col);
}