float h = (angle + M_PI) * 6.0 / (2.0 * M_PI);
float X = c * (1.0 - fabs(fmod(h, 2.0) - 1.0));
float r = 0.0f, g = 0.0f, b = 0.0f;
float h = (angle + M_PI) * 6.0 / (2.0 * M_PI);
float X = c * (1.0 - fabs(fmod(h, 2.0) - 1.0));
float r = 0.0f, g = 0.0f, b = 0.0f;