// HDRBloom closest-hit (runs in SHADE). Half the cubes are "emitters" that
// accumulate a strongly super-1.0 radiance (the HDR signal a bloom pass
// extracts); the rest are dim Lambert-shaded fillers near/below 1.0 that the
// threshold rejects. The linear accumulator is what RESOLVE writes into the
// rgba16float scene target — no tonemap here.
//
// Payload declared here so the assembler sees it before wfPayload / SHADE.
struct Payload {
    color: vec3<f32>,
};

const SUN_DIR_TO_LIGHT: vec3<f32> = vec3<f32>(0.40, 0.85, 0.35);
const AMBIENT_COLOR:    vec3<f32> = vec3<f32>(0.10, 0.11, 0.16);

// Distinct per-instance hue so emitters read as different coloured glows.
fn instanceAlbedo(i: u32) -> vec3<f32> {
    let h = i * 2654435761u;
    return vec3<f32>(
        0.35 + 0.6 * f32((h >>  0u) & 255u) / 255.0,
        0.35 + 0.6 * f32((h >>  8u) & 255u) / 255.0,
        0.35 + 0.6 * f32((h >> 16u) & 255u) / 255.0);
}

fn closesthit_main(ray: RayDesc, hit: HitInfo, payload: ptr<function, Payload>) {
    let meshRec = meshRecords[tlasEntries[hit.instanceId].blasMeshIdx];
    let verts = _rtFetchTri(meshRec, hit.primitiveId);
    let nObj = normalize(cross(verts[1] - verts[0], verts[2] - verts[0]));
    let nWorld = normalize(vec3<f32>(
        dot(hit.objectToWorldR0.xyz, nObj),
        dot(hit.objectToWorldR1.xyz, nObj),
        dot(hit.objectToWorldR2.xyz, nObj)));

    let albedo  = instanceAlbedo(hit.customIndex);
    let viewDir = -ray.direction;
    let nFacing = select(-nWorld, nWorld, dot(nWorld, viewDir) > 0.0);
    let nDotL   = max(0.0, dot(nFacing, normalize(SUN_DIR_TO_LIGHT)));

    // Every third cube is a bright emitter (HDR, > 1.0); the rest stay dim.
    if ((hit.customIndex % 3u) == 0u) {
        // View-independent emission so the whole face glows uniformly.
        rtAccumulate(albedo * 9.0);
    } else {
        rtAccumulate(albedo * (AMBIENT_COLOR + vec3<f32>(0.55 * nDotL)));
    }
}