Noise on noise: add layers by hand

One layer of noise is smooth but boring: all the blobs are the same size. Real clouds, rock and flames have big shapes plus smaller details plus tiny details.

You can fake that by adding the same noise at different sizes:

• Layer 1: normal size, strong (x 0.5).
• Layer 2: twice as small (multiply the position by 2), half as strong (x 0.25).
• Layer 3: four times as small, quarter as strong (x 0.125).

Each layer has half the strength and twice the detail of the one before. Adding a different offset to each layer stops them lining up.

float2 p = uv * float2(4.0, 3.0);
float n = 0.5 * vnoise(p);
n += 0.25 * vnoise(p * 2.0 + float2(13.7, 7.1));
n += 0.125 * vnoise(p * 4.0 + float2(27.4, 14.2));

Next lesson puts this in a loop. First do it by hand so you can see what the loop will do.