4 // https://github.com/KhronosGroup/glTF-Sample-Viewer/blob/glTF-WebGL-PBR/shaders/pbr-frag.glsl
5 // Commit dc84b5e374fb3d23153d2248a338ef88173f9eb6
7 // This fragment shader defines a reference implementation for Physically Based Shading of
8 // a microfacet surface material defined by a glTF model.For the DamagedHelmet.gltf and its Assets
11 // [1] Real Shading in Unreal Engine 4
12 // http://blog.selfshadow.com/publications/s2013-shading-course/karis/s2013_pbs_epic_notes_v2.pdf
13 // [2] Physically Based Shading at Disney
14 // http://blog.selfshadow.com/publications/s2012-shading-course/burley/s2012_pbs_disney_brdf_notes_v3.pdf
15 // [3] README.md - Environment Maps
16 // https://github.com/KhronosGroup/glTF-Sample-Viewer/#environment-maps
17 // [4] \"An Inexpensive BRDF Model for Physically based Rendering\" by Christophe Schlick
18 // https://www.cs.virginia.edu/~jdl/bib/appearance/analytic%20models/schlick94b.pdf
21 precision highp float;
23 precision mediump float;
32 #endif //GLTF_CHANNELS
34 uniform lowp vec4 uColor; // Color from SceneGraph
35 uniform lowp vec4 uColorFactor; // Color from material
36 uniform lowp float uMetallicFactor;
37 uniform lowp float uRoughnessFactor;
38 uniform lowp float uDielectricSpecular;
42 uniform sampler2D sAlbedoAlpha;
43 #endif // BASECOLOR_TEX
44 #ifdef METALLIC_ROUGHNESS_TEX
45 uniform sampler2D sMetalRoughness;
46 #endif // METALLIC_ROUGHNESS_TEX
48 uniform sampler2D sNormal;
49 uniform float uNormalScale;
52 uniform sampler2D sAlbedoMetal;
53 uniform sampler2D sNormalRoughness;
57 uniform sampler2D sOcclusion;
58 uniform float uOcclusionStrength;
61 #ifdef EMISSIVE_TEXTURE
62 uniform sampler2D sEmissive;
64 uniform vec3 uEmissiveFactor;
66 uniform float uSpecularFactor;
67 uniform vec3 uSpecularColorFactor;
68 #ifdef MATERIAL_SPECULAR_TEXTURE
69 uniform sampler2D sSpecular;
71 #ifdef MATERIAL_SPECULAR_COLOR_TEXTURE
72 uniform sampler2D sSpecularColor;
76 uniform sampler2D sbrdfLUT;
77 uniform samplerCube sDiffuseEnvSampler;
78 uniform samplerCube sSpecularEnvSampler;
79 uniform float uIblIntensity;
80 uniform mediump vec3 uYDirection;
81 uniform float uMaxLOD;
84 uniform lowp float uOpaque;
85 uniform lowp float uMask;
86 uniform lowp float uAlphaThreshold;
88 // TODO: Multiple texture coordinate will be supported.
92 in highp vec3 vPositionToCamera;
96 const float c_MinRoughness = 0.04;
98 vec3 linear(vec3 color)
100 return pow(color, vec3(2.2));
105 // Metallic and Roughness material properties are packed together
106 // In glTF, these factors can be specified by fixed scalar values
107 // or from a metallic-roughness map
108 // Roughness is stored in the 'g' channel, metallic is stored in the 'b' channel.
109 // This layout intentionally reserves the 'r' channel for (optional) occlusion map data
110 lowp float metallic = uMetallicFactor;
111 lowp float perceptualRoughness = uRoughnessFactor;
112 // If there isn't normal texture, use surface normal
113 mediump vec3 n = normalize(vTBN[2].xyz);
116 // The albedo may be defined from a base texture or a flat color
118 lowp vec4 baseColor = texture(sAlbedoAlpha, vUV);
119 baseColor = vColor * vec4(linear(baseColor.rgb), baseColor.w) * uColorFactor;
120 #else // BASECOLOR_TEX
121 lowp vec4 baseColor = vColor * uColorFactor;
122 #endif // BASECOLOR_TEX
124 #ifdef METALLIC_ROUGHNESS_TEX
125 lowp vec4 metrou = texture(sMetalRoughness, vUV);
126 metallic = metrou.METALLIC * metallic;
127 perceptualRoughness = metrou.ROUGHNESS * perceptualRoughness;
128 #endif // METALLIC_ROUGHNESS_TEX
131 n = texture(sNormal, vUV).rgb;
132 n = normalize(vTBN * ((2.0 * n - 1.0) * vec3(uNormalScale, uNormalScale, 1.0)));
135 vec4 albedoMetal = texture(sAlbedoMetal, vUV);
136 lowp vec4 baseColor = vec4(linear(albedoMetal.rgb), 1.0) * vColor * uColorFactor;
138 metallic = albedoMetal.METALLIC * metallic;
140 vec4 normalRoughness = texture(sNormalRoughness, vUV);
141 perceptualRoughness = normalRoughness.ROUGHNESS * perceptualRoughness;
143 n = normalRoughness.rgb;
144 n = normalize(vTBN * ((2.0 * n - 1.0) * vec3(uNormalScale, uNormalScale, 1.0)));
147 // The value of uOpaque and uMask can be 0.0 or 1.0.
148 // If uMask is 1.0, a Pixel that has bigger alpha than uAlphaThreashold becomes fully opaque,
149 // and, a pixel that has smaller alpha than uAlphaThreashold becomes fully transparent.
150 // If uOpaque is 1.0, alpha value of final color is 1.0;
151 // https://www.khronos.org/registry/glTF/specs/2.0/glTF-2.0.html#_material_alphamode
152 if(uMask > 0.5 && baseColor.a < uAlphaThreshold)
156 baseColor.a = mix(baseColor.a, 1.0, uOpaque);
158 metallic = clamp(metallic, 0.0, 1.0);
159 // Roughness is authored as perceptual roughness; as is convention,
160 // convert to material roughness by squaring the perceptual roughness [2].
161 perceptualRoughness = clamp(perceptualRoughness, c_MinRoughness, 1.0);
164 lowp vec3 f0 = vec3(uDielectricSpecular);
167 float specularWeight = 1.0;
168 vec4 materialSpecularTexture = vec4(1.0);
169 #ifdef MATERIAL_SPECULAR_TEXTURE
170 materialSpecularTexture.a = texture(sSpecular, vUV).a;
172 #ifdef MATERIAL_SPECULAR_COLOR_TEXTURE
173 materialSpecularTexture.rgb = texture(sSpecularColor, vUV).rgb;
175 specularWeight = uSpecularFactor * materialSpecularTexture.a;
176 f0 = min(f0 * uSpecularColorFactor * materialSpecularTexture.rgb, vec3(1.0));
177 f0 = mix(f0, baseColor.rgb, metallic);
179 mediump vec3 v = normalize(vPositionToCamera); // Vector from surface point to camera
180 mediump float NdotV = clamp(abs(dot(n, v)), 0.001, 1.0);
181 mediump vec3 reflection = -normalize(reflect(v, n));
182 lowp vec3 brdf = texture(sbrdfLUT, vec2(NdotV, 1.0 - perceptualRoughness)).rgb;
183 vec3 Fr = max(vec3(1.0 - perceptualRoughness), f0) - f0;
184 vec3 k_S = f0 + Fr * pow(1.0 - NdotV, 5.0);
185 vec3 FssEss = specularWeight * (k_S * brdf.x + brdf.y);
188 // uMaxLOD that means mipmap level of specular texture is used for bluring of reflection of specular following roughness.
189 float lod = perceptualRoughness * (uMaxLOD - 1.0);
190 lowp vec3 specularLight = linear(textureLod(sSpecularEnvSampler, reflection * uYDirection, lod).rgb);
191 lowp vec3 specular = specularLight * FssEss;
194 lowp vec3 diffuseColor = mix(baseColor.rgb, vec3(0), metallic);
195 lowp vec3 irradiance = linear(texture(sDiffuseEnvSampler, n * uYDirection).rgb);
196 float Ems = (1.0 - (brdf.x + brdf.y));
197 vec3 F_avg = specularWeight * (f0 + (1.0 - f0) / 21.0);
198 vec3 FmsEms = Ems * FssEss * F_avg / (1.0 - F_avg * Ems);
199 vec3 k_D = diffuseColor * (1.0 - FssEss + FmsEms);
200 lowp vec3 diffuse = (FmsEms + k_D) * irradiance;
202 lowp vec3 color = (diffuse + specular) * uIblIntensity;
205 lowp float ao = texture(sOcclusion, vUV).r;
206 color = mix(color, color * ao, uOcclusionStrength);
209 #ifdef EMISSIVE_TEXTURE
210 lowp vec3 emissive = linear(texture(sEmissive, vUV).rgb) * uEmissiveFactor;
212 lowp vec3 emissive = uEmissiveFactor;
213 #endif // EMISSIVE_TEXTURE
216 FragColor = vec4(pow(color, vec3(1.0 / 2.2)), baseColor.a) * uColor;