@luma.gl/shadertools
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Shader module system for luma.gl
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JavaScript
// This fragment shader defines a reference implementation for Physically Based Shading of
// a microfacet surface material defined by a glTF model.
//
// Attribution:
// MIT license, Copyright (c) 2016-2017 Mohamad Moneimne and Contributors
// TODO - better do the checks outside of shader
export default `\
// WebGL 1.0 does not support non-constant in for loops
// This provides an easy way to handle these cases
// and still take advantage of WebGL 2.0
precision highp float;
uniform bool pbr_uUnlit;
uniform samplerCube u_DiffuseEnvSampler;
uniform samplerCube u_SpecularEnvSampler;
uniform sampler2D u_brdfLUT;
uniform vec2 u_ScaleIBLAmbient;
uniform sampler2D u_BaseColorSampler;
uniform sampler2D u_NormalSampler;
uniform float u_NormalScale;
uniform sampler2D u_EmissiveSampler;
uniform vec3 u_EmissiveFactor;
uniform sampler2D u_MetallicRoughnessSampler;
uniform sampler2D u_OcclusionSampler;
uniform float u_OcclusionStrength;
uniform float u_AlphaCutoff;
uniform vec2 u_MetallicRoughnessValues;
uniform vec4 u_BaseColorFactor;
uniform vec3 u_Camera;
// debugging flags used for shader output of intermediate PBR variables
uniform vec4 u_ScaleDiffBaseMR;
uniform vec4 u_ScaleFGDSpec;
varying vec3 pbr_vPosition;
varying vec2 pbr_vUV;
varying mat3 pbr_vTBN;
varying vec3 pbr_vNormal;
// Encapsulate the various inputs used by the various functions in the shading equation
// We store values in this struct to simplify the integration of alternative implementations
// of the shading terms, outlined in the Readme.MD Appendix.
struct PBRInfo
{
float NdotL; // cos angle between normal and light direction
float NdotV; // cos angle between normal and view direction
float NdotH; // cos angle between normal and half vector
float LdotH; // cos angle between light direction and half vector
float VdotH; // cos angle between view direction and half vector
float perceptualRoughness; // roughness value, as authored by the model creator (input to shader)
float metalness; // metallic value at the surface
vec3 reflectance0; // full reflectance color (normal incidence angle)
vec3 reflectance90; // reflectance color at grazing angle
float alphaRoughness; // roughness mapped to a more linear change in the roughness (proposed by [2])
vec3 diffuseColor; // color contribution from diffuse lighting
vec3 specularColor; // color contribution from specular lighting
vec3 n; // normal at surface point
vec3 v; // vector from surface point to camera
};
const float M_PI = 3.141592653589793;
const float c_MinRoughness = 0.04;
vec4 SRGBtoLINEAR(vec4 srgbIn)
{
vec3 linOut = pow(srgbIn.xyz,vec3(2.2));
vec3 bLess = step(vec3(0.04045),srgbIn.xyz);
vec3 linOut = mix( srgbIn.xyz/vec3(12.92), pow((srgbIn.xyz+vec3(0.055))/vec3(1.055),vec3(2.4)), bLess );
return vec4(linOut,srgbIn.w);;
return srgbIn;
}
// Find the normal for this fragment, pulling either from a predefined normal map
// or from the interpolated mesh normal and tangent attributes.
vec3 getNormal()
{
// Retrieve the tangent space matrix
vec3 pos_dx = dFdx(pbr_vPosition);
vec3 pos_dy = dFdy(pbr_vPosition);
vec3 tex_dx = dFdx(vec3(pbr_vUV, 0.0));
vec3 tex_dy = dFdy(vec3(pbr_vUV, 0.0));
vec3 t = (tex_dy.t * pos_dx - tex_dx.t * pos_dy) / (tex_dx.s * tex_dy.t - tex_dy.s * tex_dx.t);
vec3 ng = normalize(pbr_vNormal);
vec3 ng = cross(pos_dx, pos_dy);
t = normalize(t - ng * dot(ng, t));
vec3 b = normalize(cross(ng, t));
mat3 tbn = mat3(t, b, ng);
mat3 tbn = pbr_vTBN;
vec3 n = texture2D(u_NormalSampler, pbr_vUV).rgb;
n = normalize(tbn * ((2.0 * n - 1.0) * vec3(u_NormalScale, u_NormalScale, 1.0)));
// The tbn matrix is linearly interpolated, so we need to re-normalize
vec3 n = normalize(tbn[2].xyz);
return n;
}
// Calculation of the lighting contribution from an optional Image Based Light source.
// Precomputed Environment Maps are required uniform inputs and are computed as outlined in [1].
// See our README.md on Environment Maps [3] for additional discussion.
vec3 getIBLContribution(PBRInfo pbrInputs, vec3 n, vec3 reflection)
{
float mipCount = 9.0; // resolution of 512x512
float lod = (pbrInputs.perceptualRoughness * mipCount);
// retrieve a scale and bias to F0. See [1], Figure 3
vec3 brdf = SRGBtoLINEAR(texture2D(u_brdfLUT,
vec2(pbrInputs.NdotV, 1.0 - pbrInputs.perceptualRoughness))).rgb;
vec3 diffuseLight = SRGBtoLINEAR(textureCube(u_DiffuseEnvSampler, n)).rgb;
vec3 specularLight = SRGBtoLINEAR(textureCubeLod(u_SpecularEnvSampler, reflection, lod)).rgb;
vec3 specularLight = SRGBtoLINEAR(textureCube(u_SpecularEnvSampler, reflection)).rgb;
vec3 diffuse = diffuseLight * pbrInputs.diffuseColor;
vec3 specular = specularLight * (pbrInputs.specularColor * brdf.x + brdf.y);
// For presentation, this allows us to disable IBL terms
diffuse *= u_ScaleIBLAmbient.x;
specular *= u_ScaleIBLAmbient.y;
return diffuse + specular;
}
// Basic Lambertian diffuse
// Implementation from Lambert's Photometria https://archive.org/details/lambertsphotome00lambgoog
// See also [1], Equation 1
vec3 diffuse(PBRInfo pbrInputs)
{
return pbrInputs.diffuseColor / M_PI;
}
// The following equation models the Fresnel reflectance term of the spec equation (aka F())
// Implementation of fresnel from [4], Equation 15
vec3 specularReflection(PBRInfo pbrInputs)
{
return pbrInputs.reflectance0 +
(pbrInputs.reflectance90 - pbrInputs.reflectance0) *
pow(clamp(1.0 - pbrInputs.VdotH, 0.0, 1.0), 5.0);
}
// This calculates the specular geometric attenuation (aka G()),
// where rougher material will reflect less light back to the viewer.
// This implementation is based on [1] Equation 4, and we adopt their modifications to
// alphaRoughness as input as originally proposed in [2].
float geometricOcclusion(PBRInfo pbrInputs)
{
float NdotL = pbrInputs.NdotL;
float NdotV = pbrInputs.NdotV;
float r = pbrInputs.alphaRoughness;
float attenuationL = 2.0 * NdotL / (NdotL + sqrt(r * r + (1.0 - r * r) * (NdotL * NdotL)));
float attenuationV = 2.0 * NdotV / (NdotV + sqrt(r * r + (1.0 - r * r) * (NdotV * NdotV)));
return attenuationL * attenuationV;
}
// The following equation(s) model the distribution of microfacet normals across
// the area being drawn (aka D())
// Implementation from "Average Irregularity Representation of a Roughened Surface
// for Ray Reflection" by T. S. Trowbridge, and K. P. Reitz
// Follows the distribution function recommended in the SIGGRAPH 2013 course notes
// from EPIC Games [1], Equation 3.
float microfacetDistribution(PBRInfo pbrInputs)
{
float roughnessSq = pbrInputs.alphaRoughness * pbrInputs.alphaRoughness;
float f = (pbrInputs.NdotH * roughnessSq - pbrInputs.NdotH) * pbrInputs.NdotH + 1.0;
return roughnessSq / (M_PI * f * f);
}
void PBRInfo_setAmbientLight(inout PBRInfo pbrInputs) {
pbrInputs.NdotL = 1.0;
pbrInputs.NdotH = 0.0;
pbrInputs.LdotH = 0.0;
pbrInputs.VdotH = 1.0;
}
void PBRInfo_setDirectionalLight(inout PBRInfo pbrInputs, vec3 lightDirection) {
vec3 n = pbrInputs.n;
vec3 v = pbrInputs.v;
vec3 l = normalize(lightDirection); // Vector from surface point to light
vec3 h = normalize(l+v); // Half vector between both l and v
pbrInputs.NdotL = clamp(dot(n, l), 0.001, 1.0);
pbrInputs.NdotH = clamp(dot(n, h), 0.0, 1.0);
pbrInputs.LdotH = clamp(dot(l, h), 0.0, 1.0);
pbrInputs.VdotH = clamp(dot(v, h), 0.0, 1.0);
}
void PBRInfo_setPointLight(inout PBRInfo pbrInputs, PointLight pointLight) {
vec3 light_direction = normalize(pointLight.position - pbr_vPosition);
PBRInfo_setDirectionalLight(pbrInputs, light_direction);
}
vec3 calculateFinalColor(PBRInfo pbrInputs, vec3 lightColor) {
// Calculate the shading terms for the microfacet specular shading model
vec3 F = specularReflection(pbrInputs);
float G = geometricOcclusion(pbrInputs);
float D = microfacetDistribution(pbrInputs);
// Calculation of analytical lighting contribution
vec3 diffuseContrib = (1.0 - F) * diffuse(pbrInputs);
vec3 specContrib = F * G * D / (4.0 * pbrInputs.NdotL * pbrInputs.NdotV);
// Obtain final intensity as reflectance (BRDF) scaled by the energy of the light (cosine law)
return pbrInputs.NdotL * lightColor * (diffuseContrib + specContrib);
}
vec4 pbr_filterColor(vec4 colorUnused)
{
// The albedo may be defined from a base texture or a flat color
vec4 baseColor = SRGBtoLINEAR(texture2D(u_BaseColorSampler, pbr_vUV)) * u_BaseColorFactor;
vec4 baseColor = u_BaseColorFactor;
if (baseColor.a < u_AlphaCutoff) {
discard;
}
vec3 color = vec3(0, 0, 0);
if(pbr_uUnlit){
color.rgb = baseColor.rgb;
}
else{
// Metallic and Roughness material properties are packed together
// In glTF, these factors can be specified by fixed scalar values
// or from a metallic-roughness map
float perceptualRoughness = u_MetallicRoughnessValues.y;
float metallic = u_MetallicRoughnessValues.x;
// Roughness is stored in the 'g' channel, metallic is stored in the 'b' channel.
// This layout intentionally reserves the 'r' channel for (optional) occlusion map data
vec4 mrSample = texture2D(u_MetallicRoughnessSampler, pbr_vUV);
perceptualRoughness = mrSample.g * perceptualRoughness;
metallic = mrSample.b * metallic;
perceptualRoughness = clamp(perceptualRoughness, c_MinRoughness, 1.0);
metallic = clamp(metallic, 0.0, 1.0);
// Roughness is authored as perceptual roughness; as is convention,
// convert to material roughness by squaring the perceptual roughness [2].
float alphaRoughness = perceptualRoughness * perceptualRoughness;
vec3 f0 = vec3(0.04);
vec3 diffuseColor = baseColor.rgb * (vec3(1.0) - f0);
diffuseColor *= 1.0 - metallic;
vec3 specularColor = mix(f0, baseColor.rgb, metallic);
// Compute reflectance.
float reflectance = max(max(specularColor.r, specularColor.g), specularColor.b);
// For typical incident reflectance range (between 4% to 100%) set the grazing
// reflectance to 100% for typical fresnel effect.
// For very low reflectance range on highly diffuse objects (below 4%),
// incrementally reduce grazing reflecance to 0%.
float reflectance90 = clamp(reflectance * 25.0, 0.0, 1.0);
vec3 specularEnvironmentR0 = specularColor.rgb;
vec3 specularEnvironmentR90 = vec3(1.0, 1.0, 1.0) * reflectance90;
vec3 n = getNormal(); // normal at surface point
vec3 v = normalize(u_Camera - pbr_vPosition); // Vector from surface point to camera
float NdotV = clamp(abs(dot(n, v)), 0.001, 1.0);
vec3 reflection = -normalize(reflect(v, n));
PBRInfo pbrInputs = PBRInfo(
0.0, // NdotL
NdotV,
0.0, // NdotH
0.0, // LdotH
0.0, // VdotH
perceptualRoughness,
metallic,
specularEnvironmentR0,
specularEnvironmentR90,
alphaRoughness,
diffuseColor,
specularColor,
n,
v
);
// Apply ambient light
PBRInfo_setAmbientLight(pbrInputs);
color += calculateFinalColor(pbrInputs, lighting_uAmbientLight.color);
// Apply directional light
SMART_FOR(int i = 0, i < MAX_LIGHTS, i < lighting_uDirectionalLightCount, i++) {
if (i < lighting_uDirectionalLightCount) {
PBRInfo_setDirectionalLight(pbrInputs, lighting_uDirectionalLight[i].direction);
color += calculateFinalColor(pbrInputs, lighting_uDirectionalLight[i].color);
}
}
// Apply point light
SMART_FOR(int i = 0, i < MAX_LIGHTS, i < lighting_uPointLightCount, i++) {
if (i < lighting_uPointLightCount) {
PBRInfo_setPointLight(pbrInputs, lighting_uPointLight[i]);
float attenuation = getPointLightAttenuation(lighting_uPointLight[i], distance(lighting_uPointLight[i].position, pbr_vPosition));
color += calculateFinalColor(pbrInputs, lighting_uPointLight[i].color / attenuation);
}
}
// Calculate lighting contribution from image based lighting source (IBL)
color += getIBLContribution(pbrInputs, n, reflection);
// Apply optional PBR terms for additional (optional) shading
float ao = texture2D(u_OcclusionSampler, pbr_vUV).r;
color = mix(color, color * ao, u_OcclusionStrength);
vec3 emissive = SRGBtoLINEAR(texture2D(u_EmissiveSampler, pbr_vUV)).rgb * u_EmissiveFactor;
color += emissive;
// This section uses mix to override final color for reference app visualization
// of various parameters in the lighting equation.
// TODO: Figure out how to debug multiple lights
// color = mix(color, F, u_ScaleFGDSpec.x);
// color = mix(color, vec3(G), u_ScaleFGDSpec.y);
// color = mix(color, vec3(D), u_ScaleFGDSpec.z);
// color = mix(color, specContrib, u_ScaleFGDSpec.w);
// color = mix(color, diffuseContrib, u_ScaleDiffBaseMR.x);
color = mix(color, baseColor.rgb, u_ScaleDiffBaseMR.y);
color = mix(color, vec3(metallic), u_ScaleDiffBaseMR.z);
color = mix(color, vec3(perceptualRoughness), u_ScaleDiffBaseMR.w);
}
return vec4(pow(color,vec3(1.0/2.2)), baseColor.a);
}
`;