psrdnoise: 2-D demos

Various example uses of the 2-D version of psrdnoise.

• Plain noise, but periodic and with animation
• A 2-D slice of 3-D noise, shown for reference (even though this is bad practice)
• Fractal sum with displacements, Flow Noise style
• Flames or something
• Fake water waves
• Blood spatter using periodic noise
• Something... else (displacements orthogonal to the gradient)