@Name: Gaussian Blur
@Version: 1.0
@Description: Gaussian distribution using the Box-Muller transform. Use with Add=1.
@Reference: https://en.wikipedia.org/wiki/Box%E2%80%93Muller_transform
@Tags: blur
@Radius: 1.0
float r = @Radius * sqrt(-2.0*log(random(next)));
float z = 2.0 * random(next) - 1.0;
float th = 2.0 * PI * random(next) - PI;
float za = sqrt(1.0-z*z);
return r * vec3(za*cos(th), za*sin(th), z);