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#version 330 core
in vert_t {
vec3 position;
} vert;
out vec4 frag_color;
uniform samplerCube cubemap;
const float PI = 3.14159265359;
void main(void)
{
vec3 normal = normalize(vert.position);
vec3 up = vec3(0.0, 1.0, 0.0);
vec3 right = cross(up, normal);
up = cross(normal, right);
vec3 irradiance = vec3(0.0);
float delta = 0.025;
int nsamples = 0;
for (float phi = 0.0; phi < 2.0 * PI; phi += delta) {
for (float theta = 0.0; theta < 0.5 * PI; theta += delta) {
vec3 tangent = vec3(sin(theta) * cos(phi), sin(theta) * sin(phi), cos(theta));
vec3 v = tangent.x * right + tangent.y * up + tangent.z * normal;
irradiance += texture(cubemap, v).rgb * cos(theta) * sin(theta);
nsamples++;
}
}
irradiance *= PI / nsamples;
frag_color = vec4(irradiance, 1.0);
}
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