3dexperiments/assets/shaders/atmosphere.fs

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precision mediump float;
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uniform vec3 v3LightPosition;
uniform float g;
uniform float g2;
varying vec3 v3Direction;
varying vec3 c0;
varying vec3 c1;
// Calculates the Mie phase function
float getMiePhase(float fCos, float fCos2, float g, float g2){
return 1.5 * ((1.0 - g2) / (2.0 + g2)) * (1.0 + fCos2) / pow(1.0 + g2 - 2.0 * g * fCos, 1.5);
}
// Calculates the Rayleigh phase function
float getRayleighPhase(float fCos2) {
return 0.75 + 0.75 * fCos2;
}
void main (void) {
float fCos = dot(v3LightPosition, v3Direction) / length(v3Direction);
float fCos2 = fCos * fCos;
vec3 color = getRayleighPhase(fCos2) * c0 +
getMiePhase(fCos, fCos2, g, g2) * c1;
gl_FragColor = vec4(color, 1.0);
gl_FragColor.a = gl_FragColor.b;
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}