vec3 lambertianDiffuse(vec3 diffuseColor)
|
{
|
return diffuseColor / czm_pi;
|
}
|
|
vec3 fresnelSchlick2(vec3 f0, vec3 f90, float VdotH)
|
{
|
return f0 + (f90 - f0) * pow(clamp(1.0 - VdotH, 0.0, 1.0), 5.0);
|
}
|
|
float smithVisibilityG1(float NdotV, float roughness)
|
{
|
// this is the k value for direct lighting.
|
// for image based lighting it will be roughness^2 / 2
|
float k = (roughness + 1.0) * (roughness + 1.0) / 8.0;
|
return NdotV / (NdotV * (1.0 - k) + k);
|
}
|
|
float smithVisibilityGGX(float roughness, float NdotL, float NdotV)
|
{
|
return (
|
smithVisibilityG1(NdotL, roughness) *
|
smithVisibilityG1(NdotV, roughness)
|
);
|
}
|
|
float GGX(float roughness, float NdotH)
|
{
|
float roughnessSquared = roughness * roughness;
|
float f = (NdotH * roughnessSquared - NdotH) * NdotH + 1.0;
|
return roughnessSquared / (czm_pi * f * f);
|
}
|
|
/**
|
* Compute the diffuse and specular contributions using physically based
|
* rendering. This function only handles direct lighting.
|
* <p>
|
* This function only handles the lighting calculations. Metallic/roughness
|
* and specular/glossy must be handled separately. See {@czm_pbrMetallicRoughnessMaterial}, {@czm_pbrSpecularGlossinessMaterial} and {@czm_defaultPbrMaterial}
|
* </p>
|
*
|
* @name czm_pbrlighting
|
* @glslFunction
|
*
|
* @param {vec3} positionEC The position of the fragment in eye coordinates
|
* @param {vec3} normalEC The surface normal in eye coordinates
|
* @param {vec3} lightDirectionEC Unit vector pointing to the light source in eye coordinates.
|
* @param {vec3} lightColorHdr radiance of the light source. This is a HDR value.
|
* @param {czm_pbrParameters} The computed PBR parameters.
|
* @return {vec3} The computed HDR color
|
*
|
* @example
|
* czm_pbrParameters pbrParameters = czm_pbrMetallicRoughnessMaterial(
|
* baseColor,
|
* metallic,
|
* roughness
|
* );
|
* vec3 color = czm_pbrlighting(
|
* positionEC,
|
* normalEC,
|
* lightDirectionEC,
|
* lightColorHdr,
|
* pbrParameters);
|
*/
|
vec3 czm_pbrLighting(
|
vec3 positionEC,
|
vec3 normalEC,
|
vec3 lightDirectionEC,
|
vec3 lightColorHdr,
|
czm_pbrParameters pbrParameters
|
)
|
{
|
vec3 v = -normalize(positionEC);
|
vec3 l = normalize(lightDirectionEC);
|
vec3 h = normalize(v + l);
|
vec3 n = normalEC;
|
float NdotL = clamp(dot(n, l), 0.001, 1.0);
|
float NdotV = abs(dot(n, v)) + 0.001;
|
float NdotH = clamp(dot(n, h), 0.0, 1.0);
|
float LdotH = clamp(dot(l, h), 0.0, 1.0);
|
float VdotH = clamp(dot(v, h), 0.0, 1.0);
|
|
vec3 f0 = pbrParameters.f0;
|
float reflectance = max(max(f0.r, f0.g), f0.b);
|
vec3 f90 = vec3(clamp(reflectance * 25.0, 0.0, 1.0));
|
vec3 F = fresnelSchlick2(f0, f90, VdotH);
|
|
float alpha = pbrParameters.roughness;
|
float G = smithVisibilityGGX(alpha, NdotL, NdotV);
|
float D = GGX(alpha, NdotH);
|
vec3 specularContribution = F * G * D / (4.0 * NdotL * NdotV);
|
|
vec3 diffuseColor = pbrParameters.diffuseColor;
|
// F here represents the specular contribution
|
vec3 diffuseContribution = (1.0 - F) * lambertianDiffuse(diffuseColor);
|
|
// Lo = (diffuse + specular) * Li * NdotL
|
return (diffuseContribution + specularContribution) * NdotL * lightColorHdr;
|
}
|
