glsl-specular-cook-torrance's Introduction

glsl-specular-cook-torrance

Computes the specular power in the Cook-Torrance model.

Example

#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(
    lightDirection, 
    viewDirection, 
    normal, 
    roughness,
    fresnel);

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

Usage

Install with npm:

npm install glsl-specular-cook-torrance

Then use with glslify.

API

#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.