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#[compute]
#version 450
#VERSION_DEFINES
#define BLOCK_SIZE 8
layout(local_size_x = BLOCK_SIZE, local_size_y = BLOCK_SIZE, local_size_z = 1) in;
shared float tmp_data[BLOCK_SIZE * BLOCK_SIZE];
#ifdef READ_TEXTURE
//use for main texture
layout(set = 0, binding = 0) uniform sampler2D source_texture;
#else
//use for intermediate textures
layout(r32f, set = 0, binding = 0) uniform restrict readonly image2D source_luminance;
#endif
layout(r32f, set = 1, binding = 0) uniform restrict writeonly image2D dest_luminance;
#ifdef WRITE_LUMINANCE
layout(set = 2, binding = 0) uniform sampler2D prev_luminance;
#endif
layout(push_constant, std430) uniform Params {
ivec2 source_size;
float max_luminance;
float min_luminance;
float exposure_adjust;
float pad[3];
}
params;
void main() {
uint t = gl_LocalInvocationID.y * BLOCK_SIZE + gl_LocalInvocationID.x;
ivec2 pos = ivec2(gl_GlobalInvocationID.xy);
if (any(lessThan(pos, params.source_size))) {
#ifdef READ_TEXTURE
vec3 v = texelFetch(source_texture, pos, 0).rgb;
tmp_data[t] = max(v.r, max(v.g, v.b));
#else
tmp_data[t] = imageLoad(source_luminance, pos).r;
#endif
} else {
tmp_data[t] = 0.0;
}
groupMemoryBarrier();
barrier();
uint size = (BLOCK_SIZE * BLOCK_SIZE) >> 1;
do {
if (t < size) {
tmp_data[t] += tmp_data[t + size];
}
groupMemoryBarrier();
barrier();
size >>= 1;
} while (size >= 1);
if (t == 0) {
//compute rect size
ivec2 rect_size = min(params.source_size - pos, ivec2(BLOCK_SIZE));
float avg = tmp_data[0] / float(rect_size.x * rect_size.y);
//float avg = tmp_data[0] / float(BLOCK_SIZE*BLOCK_SIZE);
pos /= ivec2(BLOCK_SIZE);
#ifdef WRITE_LUMINANCE
float prev_lum = texelFetch(prev_luminance, ivec2(0, 0), 0).r; //1 pixel previous exposure
avg = clamp(prev_lum + (avg - prev_lum) * params.exposure_adjust, params.min_luminance, params.max_luminance);
#endif
imageStore(dest_luminance, pos, vec4(avg));
}
}
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