58 lines
1.4 KiB
GLSL
58 lines
1.4 KiB
GLSL
#version 420 core
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// shader outputs
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layout (location = 0) out vec4 frag;
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// color accumulation buffer
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layout (binding = 0) uniform sampler2D accum;
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// revealage threshold buffer
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layout (binding = 1) uniform sampler2D reveal;
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// epsilon number
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const float EPSILON = 0.00001f;
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const float REALLY_BIG_NUMBER = 75000.0f;
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// caluclate floating point numbers equality accurately
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bool isApproximatelyEqual(float a, float b){
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return abs(a - b) <= (abs(a) < abs(b) ? abs(b) : abs(a)) * EPSILON;
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}
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// get the max value between three values
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float max3(vec3 v) {
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return max(max(v.x, v.y), v.z);
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}
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void main(){
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// fragment coordination
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ivec2 coords = ivec2(gl_FragCoord.xy);
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// fragment revealage
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float revealage = texelFetch(reveal, coords, 0).r;
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// save the blending and color texture fetch cost if there is not a transparent fragment
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if (isApproximatelyEqual(revealage, 1.0f)){
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discard;
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}
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// fragment color
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vec4 accumulation = texelFetch(accum, coords, 0);
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//clamp accumulation to not go to INF
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if(accumulation.a > REALLY_BIG_NUMBER){
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accumulation.a = REALLY_BIG_NUMBER;
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}
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// suppress overflow
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if (isinf(max3(abs(accumulation.rgb)))){
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accumulation.rgb = vec3(accumulation.a);
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}
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// prevent floating point precision bug
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vec3 average_color = accumulation.rgb / max(accumulation.a, EPSILON);
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// blend pixels
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frag = vec4(average_color, 1.0f - revealage);
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// frag = vec4(accumulation.rgb, 1.0f - revealage);
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// frag = vec4(0,0,0,0);
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} |