//SPDX-License-Identifier: MIT
//SPDX-FileCopyrightText: Copyright (C) 2026 Catcrafts®

#version 460
#extension GL_EXT_ray_tracing : enable
#extension GL_EXT_shader_image_load_formatted : enable
#extension GL_EXT_shader_explicit_arithmetic_types_int16 : enable
#extension GL_EXT_descriptor_heap : enable
#extension GL_EXT_nonuniform_qualifier : enable

// Specialization constants: the albedo's slot in the resource heap and its
// sampler's slot in the sampler heap, as the host allocated them (image and
// sampler slots index their heaps directly; only buffer slots are offset by
// bufferStartElement). The descriptor heap has no combined image samplers,
// and glslang rejects a descriptor_heap sampler2D (#164), so the texture
// and the sampler are separate descriptors, joined where they are sampled.
// Sampling uses gl_HitAttributeEXT barycentrics as UVs — proof-of-binding
// rather than UV-correct shading. Per-vertex UV interpolation lands when
// Mesh on Vulkan exposes the data-region buffer.
layout(constant_id = 0) const uint16_t albedoSlot = 0us;
layout(constant_id = 1) const uint16_t samplerSlot = 0us;
layout(descriptor_heap) uniform texture2D textures[];
layout(descriptor_heap) uniform sampler   samplers[];

hitAttributeEXT vec2 hitAttrs;
layout(location = 0) rayPayloadInEXT vec3 hitValue;

void main() {
    vec2 bary = vec2(hitAttrs.x, hitAttrs.y);
    hitValue = texture(sampler2D(textures[albedoSlot], samplers[samplerSlot]), bary).rgb;
}