Perlin noise is a kind of gradient noise. The difference is that, in a value-noise generator, you assign a random value (from some distribution) to each grid po

Perlin noise is a kind of gradient noise. The difference is that, in a value-noise generator, you assign a random value (from some distribution) to each grid point, and then interpolate between the values. In a gradient-noise generator, you assign random gradients to each grid point, and then use dot products to produce the actual values from the gradients. There's a StackExchange discussion of the subjective differences here: http://math.stackexchange.com/questions/184121/why-is-gradient-noise-better-quality-than-value-noise http://math.stackexchange.com/questions/184121/why-is-gradie...