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//
// Fragment shader for procedurally generated toy ball
//
// Author: Bill Licea-Kane
//
// Copyright (c) 2002-2003 ATI Research
//
// See ATI-License.txt for license information
//
varying vec4 ECposition; // surface position in eye coordinates
varying vec4 ECballCenter; // ball center in eye coordinates
uniform vec4 LightDir; // light direction, should be normalized
uniform vec4 HVector; // reflection vector for infinite light source
uniform vec4 SpecularColor;
uniform vec4 Red, Yellow, Blue;
uniform vec4 HalfSpace0; // half-spaces used to define star pattern
uniform vec4 HalfSpace1;
uniform vec4 HalfSpace2;
uniform vec4 HalfSpace3;
uniform vec4 HalfSpace4;
uniform float InOrOutInit; // = -3
uniform float StripeWidth; // = 0.3
uniform float FWidth; // = 0.005
void main()
{
vec4 normal; // Analytically computed normal
vec4 p; // Point in shader space
vec4 surfColor; // Computed color of the surface
float intensity; // Computed light intensity
vec4 distance; // Computed distance values
float inorout; // Counter for computing star pattern
p.xyz = normalize(ECposition.xyz - ECballCenter.xyz); // Calculate p
p.w = 1.0;
inorout = InOrOutInit; // initialize inorout to -3
distance[0] = dot(p, HalfSpace0);
distance[1] = dot(p, HalfSpace1);
distance[2] = dot(p, HalfSpace2);
distance[3] = dot(p, HalfSpace3);
distance = smoothstep(-FWidth, FWidth, distance);
inorout += dot(distance, vec4(1.0));
distance.x = dot(p, HalfSpace4);
// distance.y = StripeWidth - abs(p.z);
distance.y = StripeWidth - abs(p.y);
distance = smoothstep(-FWidth, FWidth, distance);
inorout += distance.x;
inorout = clamp(inorout, 0.0, 1.0);
surfColor = mix(Yellow, Blue, distance.y);
surfColor = mix(surfColor, Red, inorout);
// normal = point on surface for sphere at (0,0,0)
normal = p;
// Per fragment diffuse lighting
intensity = 0.2; // ambient
intensity += 0.8 * clamp(dot(LightDir, normal), 0.0, 1.0);
surfColor *= intensity;
// Per fragment specular lighting
intensity = clamp(dot(HVector, normal), 0.0, 1.0);
intensity = pow(intensity, SpecularColor.a);
surfColor += SpecularColor * intensity;
gl_FragColor = surfColor;
}
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