#version 450

// Shadow pass vertex：光源视角写深度。
// GPUDriven：模型矩阵经 gl_InstanceIndex 从实例缓冲取（与 Forward
// 共用同一份数据），push 只带 lightVP（全 pass 一次）。
// 骨骼蒙皮与 Forward 同一套数据（binding 3/4），阴影与主体形变一致。

layout(location = 0) in vec3 inPosition;
layout(location = 4) in uvec4 inBoneIds;    // 骨骼槽（palette 下标）
layout(location = 5) in vec4 inWeights;     // 蒙皮权重（无骨骼顶点 = (1,0,0,0)）

layout(std430, set = 0, binding = 1) readonly buffer ObjectBuffer {
    mat4 models[];
} objects;

// 骨骼蒙皮：与 simple_shader.vert 同布局（Set0 binding 3/4）
layout(std430, set = 0, binding = 3) readonly buffer SkinOffsetBuffer {
    uint skinBases[];
} skinOffsets;

layout(std430, set = 0, binding = 4) readonly buffer SkinPaletteBuffer {
    mat4 bones[];
} skinPalettes;

layout(push_constant) uniform PushConstants {
    mat4 lightVP;
} pc;

mat4 SkinMatrix() {
    uint base = skinOffsets.skinBases[gl_InstanceIndex];
    return skinPalettes.bones[base + inBoneIds.x] * inWeights.x +
           skinPalettes.bones[base + inBoneIds.y] * inWeights.y +
           skinPalettes.bones[base + inBoneIds.z] * inWeights.z +
           skinPalettes.bones[base + inBoneIds.w] * inWeights.w;
}

void main() {
    mat4 skin = SkinMatrix();
    vec3 skinnedPos = (skin * vec4(inPosition, 1.0)).xyz;
    gl_Position = pc.lightVP * objects.models[gl_InstanceIndex] * vec4(skinnedPos, 1.0);
}