stk-code_catmod/data/shaders/godray.frag

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uniform sampler2D tex;
uniform vec2 sunpos;
#define SAMPLES 12
const float decaystep = 0.88;
in vec2 uv;
out vec4 FragColor;
void main()
{
vec2 texc = uv;
vec2 tosun = sunpos - texc;
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// if (dot(tosun, tosun) > 0.49) discard;
vec2 dist = tosun * 1.0/(float(SAMPLES) * 1.12);
vec3 col = texture(tex, texc).xyz;
float decay = 1.0;
for (int i = 0; i < SAMPLES; i++) {
texc += dist;
vec3 here = texture(tex, texc).xyz;
here *= decay;
col += here;
decay *= decaystep;
}
FragColor = vec4(col, 1.0) * 0.8;
}