54 lines
1.5 KiB
GLSL
54 lines
1.5 KiB
GLSL
// MinecraftPT — Exposure_CS
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// Computes the average scene luminance and smooths the exposure over time.
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// Writes the result into a 1x1 R16F image (exposureTex) read by the final pass.
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#include "/Lib/Settings.glsl"
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#include "/Lib/Utilities.glsl"
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const ivec3 workGroups = ivec3(8, 8, 1);
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layout (local_size_x = 16, local_size_y = 16) in;
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layout (r16f) uniform writeonly image2D img_exposureTex;
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uniform sampler2D colortex12;
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shared float luminanceSum[256];
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void main(){
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ivec2 texel = ivec2(gl_GlobalInvocationID.xy);
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// Downsample luminance from the HDR scene
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float lum = 0.0;
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vec2 base = vec2(texel * 4);
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for (int i = 0; i < 4; i++){
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for (int j = 0; j < 4; j++){
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vec3 color = texelFetch(colortex12, ivec2(base + vec2(i, j)), 0).rgb;
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lum += luminance(color);
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}}
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lum /= 16.0;
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// Shared reduction
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uint local = gl_LocalInvocationID.x + gl_LocalInvocationID.y * 16u;
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luminanceSum[local] = lum;
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barrier();
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if (local == 0u){
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float avg = 0.0;
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for (uint i = 0u; i < 256u; i++){
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avg += luminanceSum[i];
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}
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avg /= 256.0;
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// Target exposure (inverse of average luminance)
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float targetExposure = 1.0 / max(avg, 0.001);
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// Read previous exposure for temporal smoothing (single thread)
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float prevExposure = imageLoad(img_exposureTex, ivec2(0, 0)).r;
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if (prevExposure <= 0.0) prevExposure = 1.0;
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float adapted = mix(prevExposure, targetExposure, SMOOTH_EXPOSURE);
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adapted = clamp(adapted, 0.01, 100.0);
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imageStore(img_exposureTex, ivec2(0, 0), vec4(adapted));
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}
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} |