130 lines
4.2 KiB
GLSL
130 lines
4.2 KiB
GLSL
//This shader file is part of FLAR - Advanced Renderer for Freelancer by Schmackbolzen
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//If you use the supplied shader files you may not modify them unless you state in them what you changed
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//and also mention the source or who the author is.
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//Code based on https://learnopengl.com/PBR/IBL/Specular-IBL
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#version 330
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in vec3 WorldPos;
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uniform samplerCube environmentMap;
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uniform float roughness;
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uniform bool convertToLinear;
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uniform bool copyOnly;
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const float PI = 3.14159265359;
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vec3 ToGammaCorrected(vec3 inColor){
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return pow(inColor.rgb,1./vec3(2.2));
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}
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vec3 ToLinear(vec3 inColor){
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return pow(inColor,vec3(2.2));
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}
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// ----------------------------------------------------------------------------
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float DistributionGGX(vec3 N, vec3 H, float roughness)
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{
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float a = roughness*roughness;
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float a2 = a*a;
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float NdotH = max(dot(N, H), 0.0);
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float NdotH2 = NdotH*NdotH;
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float nom = a2;
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float denom = (NdotH2 * (a2 - 1.0) + 1.0);
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denom = PI * denom * denom + 0.0001;
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return nom / denom;
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}
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// ----------------------------------------------------------------------------
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// http://holger.dammertz.org/stuff/notes_HammersleyOnHemisphere.html
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// efficient VanDerCorpus calculation.
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float RadicalInverse_VdC(uint bits)
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{
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bits = (bits << 16u) | (bits >> 16u);
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bits = ((bits & 0x55555555u) << 1u) | ((bits & 0xAAAAAAAAu) >> 1u);
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bits = ((bits & 0x33333333u) << 2u) | ((bits & 0xCCCCCCCCu) >> 2u);
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bits = ((bits & 0x0F0F0F0Fu) << 4u) | ((bits & 0xF0F0F0F0u) >> 4u);
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bits = ((bits & 0x00FF00FFu) << 8u) | ((bits & 0xFF00FF00u) >> 8u);
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return float(bits) * 2.3283064365386963e-10; // / 0x100000000
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}
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// ----------------------------------------------------------------------------
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vec2 Hammersley(uint i, uint N)
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{
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return vec2(float(i)/float(N), RadicalInverse_VdC(i));
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}
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// ----------------------------------------------------------------------------
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vec3 ImportanceSampleGGX(vec2 Xi, vec3 N, float roughness)
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{
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float a = roughness*roughness;
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float phi = 2.0 * PI * Xi.x;
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float cosTheta = sqrt((1.0 - Xi.y) / (1.0 + (a*a - 1.0) * Xi.y));
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float sinTheta = sqrt(1.0 - cosTheta*cosTheta);
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// from spherical coordinates to cartesian coordinates - halfway vector
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vec3 H;
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H.x = cos(phi) * sinTheta;
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H.y = sin(phi) * sinTheta;
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H.z = cosTheta;
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// from tangent-space H vector to world-space sample vector
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vec3 up = abs(N.z) < 0.999 ? vec3(0.0, 0.0, 1.0) : vec3(1.0, 0.0, 0.0);
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vec3 tangent = normalize(cross(up, N));
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vec3 bitangent = cross(N, tangent);
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vec3 sampleVec = tangent * H.x + bitangent * H.y + N * H.z;
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return normalize(sampleVec);
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}
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// ----------------------------------------------------------------------------
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void main()
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{
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vec3 N = normalize(WorldPos);
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// make the simplyfying assumption that V equals R equals the normal
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vec3 R = N;
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vec3 V = R;
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if (!copyOnly)
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{
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const uint SAMPLE_COUNT = 1024u;
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vec3 prefilteredColor = vec3(0.0);
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float totalWeight = 0.0;
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for(uint i = 0u; i < SAMPLE_COUNT; ++i)
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{
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// generates a sample vector that's biased towards the preferred alignment direction (importance sampling).
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vec2 Xi = Hammersley(i, SAMPLE_COUNT);
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vec3 H = ImportanceSampleGGX(Xi, N, roughness);
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vec3 L = normalize(2.0 * dot(V, H) * H - V);
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float NdotL = max(dot(N, L), 0.0);
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if(NdotL > 0.0)
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{
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// sample from the environment's mip level based on roughness/pdf
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float D = DistributionGGX(N, H, roughness);
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float NdotH = max(dot(N, H), 0.0);
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float HdotV = max(dot(H, V), 0.0);
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float pdf = D * NdotH / (4.0 * HdotV + 0.0001);
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float resolution = 1024.0; // resolution of source cubemap (per face)
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float saTexel = 4.0 * PI / (6.0 * resolution * resolution);
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float saSample = 1.0 / (float(SAMPLE_COUNT) * pdf + 0.0001);
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float mipLevel = roughness == 0.0 ? 0.0 : 0.5 * log2(saSample / saTexel);
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vec3 texColor=textureLod(environmentMap, L, mipLevel).rgb;
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if(convertToLinear)
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texColor=ToLinear(texColor);
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prefilteredColor += texColor * NdotL;
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totalWeight += NdotL;
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}
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}
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prefilteredColor = prefilteredColor / totalWeight;
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gl_FragColor = vec4(ToGammaCorrected(prefilteredColor), 1.0);
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//gl_FragColor = vec4(prefilteredColor, 1.0);
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}
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else
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gl_FragColor = vec4(textureLod(environmentMap, V, 0).rgb, 1.0);
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}
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