Specular BDRF

Shaders/BRDFIntegration.fs

@@ -0,0 +1,111 @@
+#version 460 core
+out vec2 FragColor;
+in vec2 TexCoords;
+
+
+const float PI = 3.14159265359;
+
+
+// http://holger.dammertz.org/stuff/notes_HammersleyOnHemisphere.html
+// efficient VanDerCorpus calculation.
+float RadicalInverse_VdC(uint bits) 
+{
+     bits = (bits << 16u) | (bits >> 16u);
+     bits = ((bits & 0x55555555u) << 1u) | ((bits & 0xAAAAAAAAu) >> 1u);
+     bits = ((bits & 0x33333333u) << 2u) | ((bits & 0xCCCCCCCCu) >> 2u);
+     bits = ((bits & 0x0F0F0F0Fu) << 4u) | ((bits & 0xF0F0F0F0u) >> 4u);
+     bits = ((bits & 0x00FF00FFu) << 8u) | ((bits & 0xFF00FF00u) >> 8u);
+     return float(bits) * 2.3283064365386963e-10; // / 0x100000000
+}
+
+vec2 Hammersley(uint i, uint N)
+{
+	return vec2(float(i)/float(N), RadicalInverse_VdC(i));
+}
+
+float GeometrySchlickGGX(float NdotV, float roughness)
+{
+    float a = roughness;
+    float k = (a * a) / 2.0;
+
+    float nom   = NdotV;
+    float denom = NdotV * (1.0 - k) + k;
+
+    return nom / denom;
+}
+
+vec3 ImportanceSampleGGX(vec2 Xi, vec3 N, float roughness){
+    float a = roughness*roughness;
+
+    float phi = 2.0 * PI * Xi.x;
+    float cosTheta = sqrt((1.0 - Xi.y) / (1.0 + (a*a - 1.0) * Xi.y));
+    float sinTheta = sqrt(1.0 - cosTheta*cosTheta);
+
+    // Spherical to cartesian
+    vec3 H;
+    H.x = cos(phi) * sinTheta;
+    H.y = sin(phi) * sinTheta;
+    H.z = cosTheta;
+
+    // tangent space to world sample vector
+    vec3 up = abs(N.z) < 0.999 ? vec3(0.0, 0.0, 1.0) : vec3(1.0, 0.0, 0.0);
+    vec3 tangent = normalize(cross(up,N));
+    vec3 bitangent = cross(N, tangent);
+    vec3 sampleVec = tangent * H.x + bitangent * H.y + N * H.z;
+
+    return normalize(sampleVec);
+}
+
+
+float GeometrySmith(vec3 N, vec3 V, vec3 L, float roughness)
+{
+    float NdotV = max(dot(N, V), 0.0);
+    float NdotL = max(dot(N, L), 0.0);
+    float ggx2 = GeometrySchlickGGX(NdotV, roughness);
+    float ggx1 = GeometrySchlickGGX(NdotL, roughness);
+
+    return ggx1 * ggx2;
+}  
+
+vec2 IntegrateBRDF (float NdotV, float roughness){
+
+    vec3 V;
+    V.x = sqrt(1.0 - NdotV * NdotV);
+    V.y = 0.0;
+    V.z = NdotV;
+
+    float A = 0.0;
+    float B = 0.0;
+    
+    vec3 N = vec3(0.0,0.0,1.0);
+
+    const uint SAMPLE_COUNT = 1024u;
+    for(uint i = 0u; i < SAMPLE_COUNT; ++i){
+       vec2 Xi = Hammersley(i, SAMPLE_COUNT);
+        vec3 H  = ImportanceSampleGGX(Xi, N, roughness);
+        vec3 L  = normalize(2.0 * dot(V, H) * H - V);
+
+        float NdotL = max(L.z, 0.0);
+        float NdotH = max(H.z, 0.0);
+        float VdotH = max(dot(V, H), 0.0);
+
+        if(NdotL > 0.0)
+        {
+            float G = GeometrySmith(N, V, L, roughness);
+            float G_Vis = (G * VdotH) / (NdotH * NdotV);
+            float Fc = pow(1.0 - VdotH, 5.0);
+
+            A += (1.0 - Fc) * G_Vis;
+            B += Fc * G_Vis;
+        }
+    }
+    A /= float(SAMPLE_COUNT);
+    B /= float(SAMPLE_COUNT);
+    return vec2(A, B);
+}
+
+void main() 
+{
+    vec2 integratedBRDF = IntegrateBRDF(TexCoords.x, TexCoords.y);
+    FragColor = integratedBRDF;
+}

Shaders/BRDFIntegration.vs

@@ -0,0 +1,10 @@
+#version 460 core
+layout (location = 0) in vec3 aPos;
+layout (location = 1) in vec2 aTexCoords;
+
+out vec2 TexCoords;
+
+void main(){
+    TexCoords = aTexCoords;
+    gl_Position = vec4(aPos, 1.0);
+}

Shaders/HDRSkybox.fs

@@ -7,7 +7,6 @@ uniform samplerCube environmentMap;
 
 void main(){
     vec3 envColor = texture(environmentMap, localPos).rgb;
-
     envColor = envColor /(envColor + vec3(1.0));
     envColor = pow(envColor, vec3(1.0/2.2));
 

Shaders/pbr.fs

@@ -12,9 +12,12 @@ uniform sampler2D metallicMap;
 uniform sampler2D normalMap;
 uniform sampler2D roughnessMap;
 uniform sampler2D aoMap;
-uniform samplerCube irradianceMap;
 
 
+uniform samplerCube irradianceMap;
+uniform samplerCube prefilterMap;
+uniform sampler2D brdfLUT;
+
 uniform vec3 lightPositions[4];
 uniform vec3 lightColors[4];
 
@@ -78,6 +81,8 @@ vec3 getNormalFromNormalMap(){
     return normalize(TBN * tangentNormal);
 }
 
+
+
 void main(){
 
     vec3 albedo = pow(texture(albedoMap, TexCoords).rgb, vec3(2.2));
@@ -88,6 +93,8 @@ void main(){
 
     vec3 N = getNormalFromNormalMap();
     vec3 V = normalize(camPos - WorldPos);
+    vec3 R = reflect(-V, N);
+
 
     vec3 F0 = vec3(0.04);
     F0 = mix(F0, albedo, metallic);
@@ -128,7 +135,15 @@ void main(){
     kD *= 1.0 - metallic;
     vec3 irradiance = texture(irradianceMap, N).rgb;
     vec3 diffuse = irradiance* albedo;
-    vec3 ambient = (kD * diffuse) * ao;
+
+    const float MAX_REFLECTION_LOD = 4.0;
+    vec3 prefilterColor = textureLod(prefilterMap, R, roughness * MAX_REFLECTION_LOD).rgb;
+    vec2 envBRDF = texture(brdfLUT, vec2(max(dot(N,V), 0.0), roughness)).rg;
+    vec3 specular = prefilterColor * (kS * envBRDF.x + envBRDF.y);
+
+
+
+    vec3 ambient = (kD * diffuse + specular) * ao;
     vec3 color = ambient + Lo;
 
     // HDR tonemapping

Shaders/prefilter.fs

@@ -0,0 +1,71 @@
+#version 460 core
+out vec4 FragColor;
+in vec3 localPos;
+
+uniform samplerCube environmentMap;
+uniform float roughness;
+
+const float PI = 3.14159265359;
+
+vec3 ImportanceSampleGGX(vec2 Xi, vec3 N, float roughness){
+    float a = roughness*roughness;
+
+    float phi = 2.0 * PI * Xi.x;
+    float cosTheta = sqrt((1.0 - Xi.y) / (1.0 + (a*a - 1.0) * Xi.y));
+    float sinTheta = sqrt(1.0 - cosTheta*cosTheta);
+
+    // Spherical to cartesian
+    vec3 H;
+    H.x = cos(phi) * sinTheta;
+    H.y = sin(phi) * sinTheta;
+    H.z = cosTheta;
+
+    // tangent space to world sample vector
+    vec3 up = abs(N.z) < 0.999 ? vec3(0.0, 0.0, 1.0) : vec3(1.0, 0.0, 0.0);
+    vec3 tangent = normalize(cross(up,N));
+    vec3 bitangent = cross(N, tangent);
+    vec3 sampleVec = tangent * H.x + bitangent * H.y + N * H.z;
+
+    return normalize(sampleVec);
+}
+
+
+// Generate Van Der Corput sequence
+float RadicalInverse_VdC(uint bits){
+    bits = (bits << 16u) | (bits >> 16u);
+    bits = ((bits & 0x55555555u) << 1u) | ((bits & 0xAAAAAAAAu) >> 1u);
+    bits = ((bits & 0x33333333u) << 2u) | ((bits & 0xCCCCCCCCu) >> 2u);
+    bits = ((bits & 0x0F0F0F0Fu) << 4u) | ((bits & 0xF0F0F0F0u) >> 4u);
+    bits = ((bits & 0x00FF00FFu) << 8u) | ((bits & 0xFF00FF00u) >> 8u);
+    return float(bits) * 2.3283064365386963e-10; // / 0x100000000
+}
+
+vec2 Hammersley(uint i, uint N){
+    return vec2(float(i)/float(N), RadicalInverse_VdC(i));
+}
+
+void main(){
+    vec3 N = normalize(localPos);
+    vec3 R = N;
+    vec3 V = R;
+    
+    const uint SAMPLE_COUNT = 1024u;
+    float totalWeight = 0.0;
+    vec3 prefilteredColor = vec3(0.0);
+    for(uint i = 0u; i < SAMPLE_COUNT; ++i)
+    {
+        vec2 Xi = Hammersley(i, SAMPLE_COUNT);
+        vec3 H = ImportanceSampleGGX(Xi, N, roughness);
+        vec3 L = normalize(2.0 * dot(V,H) * H - V );
+
+        float NdotL = max(dot(N, L), 0.0);
+        if(NdotL > 0.0){
+            prefilteredColor += texture(environmentMap, L).rgb * NdotL;
+            totalWeight += NdotL;
+        }
+    }
+
+    prefilteredColor = prefilteredColor / totalWeight;
+
+    FragColor = vec4(prefilteredColor, 1.0);
+}

src/Renderer/Renderer.cpp

@@ -119,12 +119,45 @@ void renderCube() {
     glBindVertexArray(0);
 }
 
+unsigned int quadVAO = 0;
+unsigned int quadVBO;
+void renderQuad()
+{
+    if (quadVAO == 0)
+    {
+        float quadVertices[] = {
+            // positions        // texture Coords
+            -1.0f,  1.0f, 0.0f, 0.0f, 1.0f,
+            -1.0f, -1.0f, 0.0f, 0.0f, 0.0f,
+             1.0f,  1.0f, 0.0f, 1.0f, 1.0f,
+             1.0f, -1.0f, 0.0f, 1.0f, 0.0f,
+        };
+        // setup plane VAO
+        glGenVertexArrays(1, &quadVAO);
+        glGenBuffers(1, &quadVBO);
+        glBindVertexArray(quadVAO);
+        glBindBuffer(GL_ARRAY_BUFFER, quadVBO);
+        glBufferData(GL_ARRAY_BUFFER, sizeof(quadVertices), &quadVertices, GL_STATIC_DRAW);
+        glEnableVertexAttribArray(0);
+        glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)0);
+        glEnableVertexAttribArray(1);
+        glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)(3 * sizeof(float)));
+    }
+    glBindVertexArray(quadVAO);
+    glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
+    glBindVertexArray(0);
+}
 
+
+
+unsigned int brdfLUTTexture;
+unsigned int prefilterMap;
 unsigned int irradianceMap;
 unsigned int envCubemap;
 unsigned int envMapVAO;
 void Renderer::Setup()
 {
+    glEnable(GL_TEXTURE_CUBE_MAP_SEAMLESS);
     // Create ScreenVAO
     glGenVertexArrays(1, &ScreenVAO);
     glBindVertexArray(ScreenVAO);
@@ -158,11 +191,11 @@ void Renderer::Setup()
     shaders[static_cast<int>(RenderPass::PBR)].Load("../Shaders/pbr.vs", "../Shaders/pbr.fs");
 
 
-    albedo = TextureFromFile("../Textures/rusted_iron/albedo.png", ".");
+    albedo = TextureFromFile("../Textures/space-cruiser/albedo.png", ".");
-    normal = TextureFromFile("../Textures/rusted_iron/normal.png", ".");
+    normal = TextureFromFile("../Textures/space-cruiser/normal.png", ".");
-    metallic = TextureFromFile("../Textures/rusted_iron/metallic.png", ".");
+    metallic = TextureFromFile("../Textures/space-cruiser/metallic.png", ".");
-    roughness = TextureFromFile("../Textures/rusted_iron/roughness.png", ".");
+    roughness = TextureFromFile("../Textures/space-cruiser/roughness.png", ".");
-    ao = TextureFromFile("../Textures/rusted_iron/ao.png",".");
+    ao = TextureFromFile("../Textures/space-cruiser/ao.png",".");
 
 
     // Create the skybox from an HDR equirectangular environment map 
@@ -199,7 +232,7 @@ void Renderer::Setup()
     auto eqShader = Shader();
     eqShader.Load("../Shaders/HDRMap.vs", "../Shaders/HDRMap.fs");
 
-    auto hdrTexture = LoadIBL("../Textures/photostudio.hdr");
+    auto hdrTexture = LoadIBL("../Textures/night_2k.hdr");
 
     eqShader.use();
     eqShader.setInt("equirectangularMap", 0);
@@ -319,6 +352,71 @@ void Renderer::Setup()
 
     glBindVertexArray(0);
 
+    glGenTextures(1, &prefilterMap);
+    glBindTexture(GL_TEXTURE_CUBE_MAP, prefilterMap);
+    for (unsigned int i = 0; i < 6; ++i) {
+        glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X + i, 0, GL_RGB16F, 128, 128, 0, GL_RGB, GL_FLOAT, nullptr);
+    }
+    glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+    glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
+    glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_R, GL_CLAMP_TO_EDGE);
+    glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
+    glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+
+    glGenerateMipmap(GL_TEXTURE_CUBE_MAP);
+
+    auto prefilterShader = Shader();
+    prefilterShader.Load("../Shaders/skybox2.vs", "../Shaders/prefilter.fs");
+    prefilterShader.setInt("environmentMap", 0);
+    prefilterShader.setMat4("projection", captureProjection);
+    glActiveTexture(GL_TEXTURE0);
+    glBindTexture(GL_TEXTURE_CUBE_MAP, envCubemap);
+
+    glBindFramebuffer(GL_FRAMEBUFFER, captureFBO);
+    unsigned int maxMipLevels = 5;
+    for (unsigned int mip = 0; mip < maxMipLevels; ++mip) {
+        unsigned int mipWidth = 128 * std::pow(0.5, mip);
+        unsigned int mipHeight = 128 * std::pow(0.5, mip);
+        glBindRenderbuffer(GL_RENDERBUFFER, captureRBO);
+        glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT24, mipWidth, mipHeight);
+        glViewport(0, 0, mipWidth, mipHeight);
+
+        float roughness = (float)mip / (float)(maxMipLevels - 1);
+        prefilterShader.setFloat("roughness", roughness);
+        for (unsigned int i = 0; i < 6; ++i) {
+            prefilterShader.setMat4("view", captureViews[i]);
+            glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_CUBE_MAP_POSITIVE_X + i, prefilterMap, mip);
+            glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+            renderCube();
+        }
+    }
+
+    glGenTextures(1, &brdfLUTTexture);
+    
+    // Pre-allocate enough memory for the LUT texture
+    glBindTexture(GL_TEXTURE_2D, brdfLUTTexture);
+    glTexImage2D(GL_TEXTURE_2D, 0, GL_RG16F, 512, 512, 0, GL_RG, GL_FLOAT, 0);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+
+    glBindFramebuffer(GL_FRAMEBUFFER, captureFBO);
+    glBindRenderbuffer(GL_RENDERBUFFER, captureRBO);
+    glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT24, 512, 512);
+    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, brdfLUTTexture, 0);
+
+    glViewport(0, 0, 512, 512);
+    auto brdfShader = Shader();
+    brdfShader.Load("../Shaders/BRDFIntegration.vs", "../Shaders/BRDFIntegration.fs");
+
+    brdfShader.use();
+    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+    renderQuad();
+
+    glViewport(0, 0, 800, 600); // reset viewport
+    glBindFramebuffer(GL_FRAMEBUFFER, 0);
+
 
 }
 
@@ -540,6 +638,9 @@ void Renderer::Render(Scene& scene)
     shader.setInt("roughnessMap", 3);
     shader.setInt("aoMap", 4);
     shader.setInt("irradianceMap", 5);
+    shader.setInt("prefilterMap", 6);
+    shader.setInt("brdfLUT", 7);
+
 
     shader.setMat4("projection", projection);
     view = scene.MainCamera.GetViewMatrix();
@@ -564,6 +665,12 @@ void Renderer::Render(Scene& scene)
     glActiveTexture(GL_TEXTURE5);
     glBindTexture(GL_TEXTURE_CUBE_MAP, irradianceMap);
 
+    glActiveTexture(GL_TEXTURE6);
+    glBindTexture(GL_TEXTURE_CUBE_MAP, prefilterMap);
+
+    glActiveTexture(GL_TEXTURE7);
+    glBindTexture(GL_TEXTURE_2D, brdfLUTTexture);
+
 
     // Render Spheres
     model = glm::mat4(1.0f);
@@ -632,12 +739,6 @@ void Renderer::Render(Scene& scene)
     */
 
     
-    
-   
-
-   
-
-    
     // 4. draw result to screen
     /*
     glBindFramebuffer(GL_FRAMEBUFFER, 0);