qt5base-lts/examples/widgets/graphicsview/boxes/refraction.fsh

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varying vec3 position, normal;
varying vec4 specular, ambient, diffuse, lightDirection;

uniform sampler2D tex;
uniform samplerCube env;
uniform mat4 view;

// Arrays don't work here on glsl < 120, apparently.
//const float coeffs[6] = float[6](1.0/2.0, 1.0/2.1, 1.0/2.2, 1.0/2.3, 1.0/2.4, 1.0/2.5);
float coeffs(int i)
{
	return 1.0 / (2.0 + 0.1 * float(i));
}

void main()
{
    vec3 N = normalize(normal);
    vec3 I = -normalize(position);
    float IdotN = dot(I, N);
    float scales[6];
    vec3 C[6];
    for (int i = 0; i < 6; ++i) {
        scales[i] = (IdotN - sqrt(1.0 - coeffs(i) + coeffs(i) * (IdotN * IdotN)));
        C[i] = textureCube(env, (-I + coeffs(i) * N) * mat3(view[0].xyz, view[1].xyz, view[2].xyz)).xyz;
    }

    gl_FragColor = 0.25 * vec4(C[5].x + 2.0*C[0].x + C[1].x, C[1].y + 2.0*C[2].y + C[3].y,
                   C[3].z + 2.0*C[4].z + C[5].z, 4.0);
}