LYGIA Shader Library

iridescence (lygia/lighting/iridescence)

based on the picture in http://home.hiroshima-u.ac.jp/kin/publications/TVC01/examples.pdf

Dependencies:

Use:

<vec3> iridescence(<float> angle, <float> thickness)

Check it on Github



#ifndef FNC_IRIDESCENCE
#define FNC_IRIDESCENCE

vec3 iridescence(float cosA, float thickness) {
    // typically the dot product of normal with eye ray
    float NxV = cosA;

    // energy of spectral colors
    float lum = 0.05064;
    // basic energy of light
    float luma = 0.01070;
    // tint of the final color
    vec3 tint = vec3(0.7333,0.89804,0.94902);
    // vec3 tint = vec3(0.49639,0.78252,0.88723);
    // interference rate at minimum angle
    float interf0 = 2.4;
    // phase shift rate at minimum angle
    float phase0 = 1.0 / 2.8;
    // interference rate at maximum angle
    float interf1 = interf0 * 4.0 / 3.0;
    // phase shift rate at maximum angle
    float phase1 = phase0;
    // fresnel (most likely completely wrong)
    float f = (NxV) * (NxV);
    float interf = mix(interf0, interf1, f);
    float phase = mix(phase0, phase1, f);
    float dp = (NxV + 1.0) * 0.5;

    // film hue
    vec3 hue = mix( hue(thickness * interf0 + dp, thickness * phase0),
                    hue(thickness * interf1 + 0.1 + dp, thickness * phase1),
                    f);

    vec3 film = hue * lum + vec3(0.49639,0.78252,0.88723) * luma;

    return (film * 3.0 + pow(f, 12.0)) * tint;
}

#endif

Examples

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