progs/glsl/CH11-toyball.frag

   1 //
   2 // Fragment shader for procedurally generated toy ball
   3 //
   4 // Author: Bill Licea-Kane
   5 //
   6 // Copyright (c) 2002-2003 ATI Research
   7 //
   8 // See ATI-License.txt for license information
   9 //
  10
  11 varying vec4 ECposition;   // surface position in eye coordinates
  12 varying vec4 ECballCenter; // ball center in eye coordinates
  13
  14 uniform vec4  LightDir;     // light direction, should be normalized
  15 uniform vec4  HVector;      // reflection vector for infinite light source
  16 uniform vec4  SpecularColor;
  17 uniform vec4  Red, Yellow, Blue;
  18
  19 uniform vec4  HalfSpace0;   // half-spaces used to define star pattern
  20 uniform vec4  HalfSpace1;
  21 uniform vec4  HalfSpace2;
  22 uniform vec4  HalfSpace3;
  23 uniform vec4  HalfSpace4;
  24
  25 uniform float InOrOutInit;  // = -3
  26 uniform float StripeWidth;  // = 0.3
  27 uniform float FWidth;       // = 0.005
  28
  29 void main()
  30 {
  31     vec4  normal;              // Analytically computed normal
  32     vec4  p;                   // Point in shader space
  33     vec4  surfColor;           // Computed color of the surface
  34     float intensity;           // Computed light intensity
  35     vec4  distance;            // Computed distance values
  36     float inorout;             // Counter for computing star pattern
  37
  38     p.xyz = normalize(ECposition.xyz - ECballCenter.xyz);    // Calculate p
  39     p.w   = 1.0;
  40
  41     inorout = InOrOutInit;     // initialize inorout to -3
  42
  43     distance[0] = dot(p, HalfSpace0);
  44     distance[1] = dot(p, HalfSpace1);
  45     distance[2] = dot(p, HalfSpace2);
  46     distance[3] = dot(p, HalfSpace3);
  47
  48     distance = smoothstep(-FWidth, FWidth, distance);
  49     inorout += dot(distance, vec4(1.0));
  50
  51     distance.x = dot(p, HalfSpace4);
  52     distance.y = StripeWidth - abs(p.z);
  53     distance = smoothstep(-FWidth, FWidth, distance);
  54     inorout += distance.x;
  55
  56     inorout = clamp(inorout, 0.0, 1.0);
  57
  58     surfColor = mix(Yellow, Red, inorout);
  59     surfColor = mix(surfColor, Blue, distance.y);
  60
  61     // normal = point on surface for sphere at (0,0,0)
  62     normal = p;
  63
  64     // Per fragment diffuse lighting
  65     intensity  = 0.2; // ambient
  66     intensity += 0.8 * clamp(dot(LightDir, normal), 0.0, 1.0);
  67     surfColor *= intensity;
  68
  69     // Per fragment specular lighting
  70     intensity  = clamp(dot(HVector, normal), 0.0, 1.0);
  71     intensity  = pow(intensity, SpecularColor.a);
  72     surfColor += SpecularColor * intensity;
  73
  74     gl_FragColor = surfColor;
  75 }