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;
33 #endif //GLTF_CHANNELS
36 uniform lowp vec4 uColor; // Color from SceneGraph
37 uniform lowp vec4 uColorFactor; // Color from material
38 uniform lowp float uMetallicFactor;
39 uniform lowp float uRoughnessFactor;
40 uniform lowp float uDielectricSpecular;
44 uniform sampler2D sAlbedoAlpha;
45 #endif // BASECOLOR_TEX
46 #ifdef METALLIC_ROUGHNESS_TEX
47 uniform sampler2D sMetalRoughness;
48 #endif // METALLIC_ROUGHNESS_TEX
50 uniform sampler2D sNormal;
51 uniform float uNormalScale;
54 uniform sampler2D sAlbedoMetal;
55 uniform sampler2D sNormalRoughness;
59 uniform sampler2D sOcclusion;
60 uniform float uOcclusionStrength;
64 uniform sampler2D sEmissive;
65 uniform vec3 uEmissiveFactor;
68 uniform float uSpecularFactor;
69 uniform vec3 uSpecularColorFactor;
70 #ifdef MATERIAL_SPECULAR_TEXTURE
71 uniform sampler2D sSpecular;
73 #ifdef MATERIAL_SPECULAR_COLOR_TEXTURE
74 uniform sampler2D sSpecularColor;
78 uniform sampler2D sbrdfLUT;
79 uniform samplerCube sDiffuseEnvSampler;
80 uniform samplerCube sSpecularEnvSampler;
81 uniform float uIblIntensity;
82 uniform vec3 uYDirection;
85 uniform lowp float uOpaque;
86 uniform lowp float uMask;
87 uniform lowp float uAlphaThreshold;
89 // TODO: Multiple texture coordinate will be supported.
93 in highp vec3 vPositionToCamera;
97 const float c_MinRoughness = 0.04;
99 vec3 linear(vec3 color)
101 return pow(color, vec3(2.2));
106 // Metallic and Roughness material properties are packed together
107 // In glTF, these factors can be specified by fixed scalar values
108 // or from a metallic-roughness map
109 // Roughness is stored in the 'g' channel, metallic is stored in the 'b' channel.
110 // This layout intentionally reserves the 'r' channel for (optional) occlusion map data
111 lowp float metallic = uMetallicFactor;
112 lowp float perceptualRoughness = uRoughnessFactor;
113 // If there isn't normal texture, use surface normal
114 mediump vec3 n = normalize(vTBN[2].xyz);
117 // The albedo may be defined from a base texture or a flat color
119 lowp vec4 baseColor = texture(sAlbedoAlpha, vUV);
120 baseColor = vec4(linear(baseColor.rgb), baseColor.w) * uColorFactor;
121 #else // BASECOLOR_TEX
122 lowp vec4 baseColor = vColor * uColorFactor;
123 #endif // BASECOLOR_TEX
125 #ifdef METALLIC_ROUGHNESS_TEX
126 lowp vec4 metrou = texture(sMetalRoughness, vUV);
127 metallic = metrou.METALLIC * metallic;
128 perceptualRoughness = metrou.ROUGHNESS * perceptualRoughness;
129 #endif // METALLIC_ROUGHNESS_TEX
132 n = texture(sNormal, vUV).rgb;
133 n = normalize(vTBN * ((2.0 * n - 1.0) * vec3(uNormalScale, uNormalScale, 1.0)));
136 vec4 albedoMetal = texture(sAlbedoMetal, vUV);
137 lowp vec4 baseColor = vec4(linear(albedoMetal.rgb), 1.0) * vColor * uColorFactor;
139 metallic = albedoMetal.METALLIC * metallic;
141 vec4 normalRoughness = texture(sNormalRoughness, vUV);
142 perceptualRoughness = normalRoughness.ROUGHNESS * perceptualRoughness;
144 n = normalRoughness.rgb;
145 n = normalize(vTBN * ((2.0 * n - 1.0) * vec3(uNormalScale, uNormalScale, 1.0)));
148 // The value of uOpaque and uMask can be 0.0 or 1.0.
149 // If uMask is 1.0, a Pixel that has bigger alpha than uAlphaThreashold becomes fully opaque,
150 // and, a pixel that has smaller alpha than uAlphaThreashold becomes fully transparent.
151 // If uOpaque is 1.0, alpha value of final color is 1.0;
152 // https://www.khronos.org/registry/glTF/specs/2.0/glTF-2.0.html#_material_alphamode
153 if(uMask > 0.5 && baseColor.a < uAlphaThreshold)
157 baseColor.a = mix(baseColor.a, 1.0, uOpaque);
159 metallic = clamp(metallic, 0.0, 1.0);
160 // Roughness is authored as perceptual roughness; as is convention,
161 // convert to material roughness by squaring the perceptual roughness [2].
162 perceptualRoughness = clamp(perceptualRoughness, c_MinRoughness, 1.0);
165 lowp vec3 f0 = vec3(uDielectricSpecular);
168 float specularWeight = 1.0;
169 vec4 materialSpecularTexture = vec4(1.0);
170 #ifdef MATERIAL_SPECULAR_TEXTURE
171 materialSpecularTexture.a = texture(sSpecular, vUV).a;
173 #ifdef MATERIAL_SPECULAR_COLOR_TEXTURE
174 materialSpecularTexture.rgb = texture(sSpecularColor, vUV).rgb;
176 specularWeight = uSpecularFactor * materialSpecularTexture.a;
177 f0 = min(f0 * uSpecularColorFactor * materialSpecularTexture.rgb, vec3(1.0));
178 f0 = mix(f0, baseColor.rgb, metallic);
180 mediump vec3 v = normalize(vPositionToCamera); // Vector from surface point to camera
181 mediump float NdotV = clamp(abs(dot(n, v)), 0.001, 1.0);
182 mediump vec3 reflection = -normalize(reflect(v, n));
183 lowp vec3 brdf = linear(texture(sbrdfLUT, vec2(NdotV, 1.0 - perceptualRoughness)).rgb);
184 vec3 Fr = max(vec3(1.0 - perceptualRoughness), f0) - f0;
185 vec3 k_S = f0 + Fr * pow(1.0 - NdotV, 5.0);
186 vec3 FssEss = specularWeight * (k_S * brdf.x + brdf.y);
189 lowp vec3 specularLight = linear(texture(sSpecularEnvSampler, reflection * uYDirection).rgb);
190 lowp vec3 specular = specularLight * FssEss;
193 lowp vec3 diffuseColor = mix(baseColor.rgb, vec3(0), metallic);
194 lowp vec3 irradiance = linear(texture(sDiffuseEnvSampler, n * uYDirection).rgb);
195 float Ems = (1.0 - (brdf.x + brdf.y));
196 vec3 F_avg = specularWeight * (f0 + (1.0 - f0) / 21.0);
197 vec3 FmsEms = Ems * FssEss * F_avg / (1.0 - F_avg * Ems);
198 vec3 k_D = diffuseColor * (1.0 - FssEss + FmsEms);
199 lowp vec3 diffuse = (FmsEms + k_D) * irradiance;
201 lowp vec3 color = (diffuse + specular) * uIblIntensity;
204 lowp float ao = texture(sOcclusion, vUV).r;
205 color = mix(color, color * ao, uOcclusionStrength);
209 lowp vec3 emissive = linear(texture(sEmissive, vUV).rgb) * uEmissiveFactor;
213 FragColor = vec4(pow(color, vec3(1.0 / 2.2)), baseColor.a) * uColor;