value = fbm_b( x, y )
then the dependant fbm looks like this:
value = fbm_b( x+a·fbm_u(x,y), y+b·fbm_v(x,y) )
I used the parameters "a" and "b" to tune the effect of the modulation (both values to zero means no modulation).
To create this image, I used then interpreted the result from the function as a heighmap, and I took the gradients to extract a surface normal. With this one, basic diffuse shading was done to shader the image, and tree aditional basic fbms where used to pick a rgb color. By usign 3D fmbs instead of 2D, and using the "time" to feed the third components, the picture above can be animated as shown in these videos.
