#version 450

// TAA resolve：时域抗锯齿。
//   1. velocity 反推历史像素位置，取历史累积色
//   2. 邻域 clamp（3×3 AABB）压制鬼影：历史色超出当前帧邻域范围的部分丢弃
//   3. mix(cur, hist, alpha) 时域累积
// 输出写入 TAAColor，它同时也是下一帧的历史（ReadHistory 自引用）。

layout(location = 0) in vec2 fragUV;
layout(location = 0) out vec4 outColor;

layout(set = 0, binding = 0) uniform sampler2D curImage;       // 当前帧 HDR
layout(set = 0, binding = 1) uniform sampler2D velocityImage;  // 运动向量（UV 空间）
layout(set = 0, binding = 2) uniform sampler2D historyImage;   // 上一帧累积结果

// 全屏 pass 通用 push（16B，程序级统一声明，VUID-08878）
layout(push_constant) uniform PushConstants {
    float exposure;   // 与其它全屏 pass 布局一致（本 pass 不用）
    float alpha;      // 历史权重（0.9 = 90% 历史）
    float param1;
    float param2;
} pc;

void main() {
    vec4 cur = texture(curImage, fragUV);
    vec2 vel = texture(velocityImage, fragUV).xy;
    vec2 histUV = fragUV - vel;

    vec3 result = cur.rgb;

    // 历史采样：越出画面（相机快速平移）直接用当前帧，不累积
    if (all(greaterThanEqual(histUV, vec2(0.0))) &&
        all(lessThanEqual(histUV, vec2(1.0)))) {
        vec3 hist = texture(historyImage, histUV).rgb;

        // 邻域 clamp：当前帧 3×3 邻域的 min/max 包围盒
        vec2 ts = 1.0 / vec2(textureSize(curImage, 0));
        vec3 minC = cur.rgb;
        vec3 maxC = cur.rgb;
        for (int y = -1; y <= 1; ++y) {
            for (int x = -1; x <= 1; ++x) {
                vec3 c = texture(curImage, fragUV + vec2(x, y) * ts).rgb;
                minC = min(minC, c);
                maxC = max(maxC, c);
            }
        }
        vec3 clamped = clamp(hist, minC, maxC);
        result = mix(cur.rgb, clamped, pc.alpha);
    }

    outColor = vec4(result, cur.a);
}