Gooch Shading

Gooch.glsl

precision highp float;
uniform float time;

uniform vec2 resolution;

varying vec3 fPosition;
varying vec3 fNormal;
varying vec3 fLight;

void main()
{  
  vec3 N = normalize(fNormal);    
  vec3 L = normalize(vec3(0.0, -10.0, 1.0));
  vec3 V = normalize(-fPosition);
  
  vec3 cHighlight = vec3(2.0, 2.0, 2.0);
  vec3 cSurface = vec3(1.0, 1.0, 1.0);
  vec3 cCool = vec3(0.0, 0.0, 0.55) + 0.25 * cSurface;
  vec3 cWarm = vec3(0.3, 0.3, 0.0) + 0.25 * cSurface;
  float T = (dot(N, L) + 1.0) * 0.5;
  vec3 R = reflect(-L, N);
  float S = clamp((100.0 * dot(R, V) - 97.0), 0.0, 1.0);  
  
  vec3 cGooch = mix(cWarm, cCool, T);  
  vec3 cShaded = mix(cGooch, cHighlight, S);
 
  gl_FragColor = vec4(cShaded, 1.0);  
}