@Name: Ikeda
@Version: 1.0
@Reference: https://en.wikipedia.org/wiki/Ikeda_map
@Tags: 2d
@U: 0.6
float t = 0.4 - 6.0 / (1.0 + p.x*p.x+p.y*p.y);
float sin_t = sin(t);
float cos_t = cos(t);
return vec3(
1.0 + @U * (p.x * cos_t - p.y * sin_t),
@U * (p.x * sin_t + p.y * cos_t),
p.z);