This shader is summing four noise terms, with each successive term being warped by the gradient of previous terms, with successively smaller impact on the total warping from each term as the sum progresses. Like before, the amount of warping increases towards the bottom of the image.
Now, we can clearly see the "billowing" and "swirling" effects that Perlin and Neyret talked about in their article. Towards the bottom of this image, the look and feel of the pattern is clearly that of billowing clouds or smoke.
This is still a 2-D pattern, created with a very reasonable number of noise values (four). Adding more terms increases the detail, but because of the texture warping, there is already some fine detail in the "crinkles" at the most strongly warped part of the pattern. Ordinary fractal sums of noise, like the rather blurry pattern at the top of the image, require more terms to generate enough detail.
Let's generate the nice pattern at the bottom for the entire canvas, and add just one more term for some more fine-grain detail!
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