  ## 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 = (1.0 - NxV) * (1.0 - NxV);
float interf = mix(interf0, interf1, f);
float phase = mix(phase0, phase1, f);
float dp = (NxV - 1.0) * 0.5;

// film hue
vec3 hue =
// fade in higher frequency at the right end
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 gamma2linear( (film * 5.0 + pow(f, 6.0)) * tint );
// return gamma2linear((film * 3.0 + pow(f, 16.0)) * tint);
// return gamma2linear(film * 5.);
}

vec3 iridescence(vec3 V, vec3 N, vec3 L, float d) {
return saturate( gamma2linear( w2rgb( abs(dot(N, -L) - dot(N, V)) * d) ) );
}

#endif
``````

Dependencies:

Use:

``````<float3> iridescence(<float> angle, <float> thickness)
``````

Check it on Github

``````

#ifndef FNC_IRIDESCENCE
#define FNC_IRIDESCENCE
float3 iridescence(float cosAngle, float thickness) {
// typically the dot product of normal with eye ray
float NxV = cosAngle;

// energy of spectral colors
float lum = 0.05064;
// basic energy of light
float luma = 0.01070;
// tint of the final color
//float3 tint = float3(0.7333,0.89804,0.94902);
float3 tint = float3(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 = (1.0 - NxV) * (1.0 - NxV);
float interf = lerp(interf0, interf1, f);
float phase = lerp(phase0, phase1, f);
float dp = (NxV - 1.0) * 0.5;

// film hue
float3 h = lerp(hue(thickness * interf0 + dp, thickness * phase0),
hue(thickness * interf1 + 0.1 + dp, thickness * phase1),
f);

float3 film = h * lum + float3(0.49639,0.78252,0.88723) * luma;

// return float3((film * 3.0 + pow(f, 12.0))) * tint;
return gamma2linear( (film * 5.0 + pow(f, 6.0)) * tint );
}

float3 iridescence(float3 V, float3 N, float3 L, float d) {
return saturate( w2rgb( abs(dot(N, -L) - dot(N, V)) * d) );
}

#endif
``````