Cook-Torrance specular/fresnel lighting term
Last updated 6 years ago by mikolalysenko .
MIT · Repository · Bugs · Original npm · Tarball · package.json
$ cnpm install glsl-specular-cook-torrance 
SYNC missed versions from official npm registry.


Computes the specular power in the Cook-Torrance model.


#pragma glslify: cookTorranceSpec = require(glsl-specular-cook-torrance)

uniform vec3 eyePosition;
uniform vec3 lightPosition;

uniform float roughness, fresnel;

varying vec3 surfacePosition, surfaceNormal;

void main() {
  //Light and view geometry
  vec3 viewDirection = normalize(eyePosition - surfacePosition);
  vec3 lightDirection = normalize(lightPosition - surfacePosition);

  //Surface properties
  vec3 normal = normalize(surfaceNormal);
  //Compute specular power
  float power = cookTorranceSpec(

  gl_FragColor = vec4(power,power,power,1.0);


Install with npm:

npm install glsl-specular-phong

Then use with glslify.


#pragma glslify: cookTorrance = require(glsl-specular-cook-torrance)
float cookTorrance(vec3 lightDir, vec3 eyeDir, vec3 normal, float roughness, float fresnel)

Computes the specular power in the Cook-Torrance

  • lightDir is a unit length vec3 pointing from the surface point toward the light
  • eyeDir is a unit length vec3 pointing from the surface point toward the camera
  • normal is the unit length surface normal at the sample point
  • roughness is the surface roughness parameter, between 0 and 1. 0 means surface is perfectly smooth, 1 means surface is matte
  • fresnel the Fresnel exponent. 0 = no Fresnel, higher values create a rim effect around objects

Returns A float representing the specular power

Note Unlike the usual Cook-Torrance model, the light power is not scaled by 1/(normal . lightDirection). This avoids an unnecessary numerically unstable division, but requires modifying how diffuse light is calculated.


(c) 2014 Mikola Lysenko. MIT License

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