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#version 150 core
// TODO: Replace with a struct
uniform vec3 kd; // Diffuse reflectivity
uniform vec3 ks; // Specular reflectivity
uniform vec3 kblue; // Cool color
uniform vec3 kyellow; // Warm color
uniform float alpha; // Fraction of diffuse added to kblue
uniform float beta; // Fraction of diffuse added to kyellow
uniform float shininess; // Specular shininess factor
uniform vec3 eyePosition;
in vec3 worldPosition;
in vec3 worldNormal;
out vec4 fragColor;
#pragma include light.inc.frag
vec3 goochModel( const in vec3 pos, const in vec3 n )
{
// Based upon the original Gooch lighting model paper at:
// http://www.cs.northwestern.edu/~ago820/SIG98/abstract.html
// Calculate kcool and kwarm from equation (3)
vec3 kcool = clamp(kblue + alpha * kd, 0.0, 1.0);
vec3 kwarm = clamp(kyellow + beta * kd, 0.0, 1.0);
vec3 result = vec3(0.0);
int i;
for (i = 0; i < lightCount; ++i) {
// Calculate the vector from the light to the fragment
vec3 s = normalize( vec3( lights[i].position ) - pos );
// Calculate the cos theta factor mapped onto the range [0,1]
float sDotNFactor = ( 1.0 + dot( s, n ) ) / 2.0;
// Calculate the tone by blending the kcool and kwarm contributions
// as per equation (2)
vec3 intensity = mix( kcool, kwarm, sDotNFactor );
// Calculate the vector from the fragment to the eye position
vec3 v = normalize( eyePosition - pos );
// Reflect the light beam using the normal at this fragment
vec3 r = reflect( -s, n );
// Calculate the specular component
float specular = 0.0;
if ( dot( s, n ) > 0.0 )
specular = pow( max( dot( r, v ), 0.0 ), shininess );
// Sum the blended tone and specular highlight
result += intensity + ks * specular;
}
return result;
}
void main()
{
fragColor = vec4( goochModel( worldPosition, normalize( worldNormal ) ), 1.0 );
}
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