50 lines
1.4 KiB
Text
50 lines
1.4 KiB
Text
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#include "common.nocompile.glsl"
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layout(local_size_x = 16, local_size_y = 16) in;
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layout(rgba32f, binding = 0) uniform image2D hdr_image;
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// adapated from https://bruop.github.io/exposure/ and http://www.alextardif.com/HistogramLuminance.html
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// Taken from RTR vol 4 pg. 278
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#define RGB_TO_LUM vec3(0.2125, 0.7154, 0.0721)
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shared uint histogram_shared[256];
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layout(std430, binding = 1) buffer HistogramBuffer {
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uint histogram[];
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};
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layout(push_constant, binding = 2) uniform readonly PushConstant{
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vec4 params;
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};
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uint color_to_bin(const vec3 hdr_color, const float min_log_lum, const float inverse_log_lum_range) {
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const float lum = dot(hdr_color, RGB_TO_LUM);
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if (lum < EPSILON) {
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return 0;
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}
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const float log_lum = clamp((log2(lum) - min_log_lum) * inverse_log_lum_range, 0.0, 1.0);
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return uint(log_lum * 254.0 + 1.0);
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}
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void main() {
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histogram_shared[gl_LocalInvocationIndex] = 0;
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groupMemoryBarrier();
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uvec2 dim = uvec2(params.zw);
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if(gl_GlobalInvocationID.x < dim.x && gl_GlobalInvocationID.y < dim.y) {
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vec3 hdr_color = imageLoad(hdr_image, ivec2(gl_GlobalInvocationID.xy)).rgb;
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uint bin_index = color_to_bin(hdr_color, params.x, params.y);
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atomicAdd(histogram_shared[bin_index], 1);
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}
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groupMemoryBarrier();
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atomicAdd(histogram[gl_LocalInvocationIndex], histogram_shared[gl_LocalInvocationIndex]);
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}
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