I’ve found an error in the GPUGems formula for Gerstner wave generation: it seems quite strange to me that nVidia guys made mistake… so I’m afraid I’m missing something! 
The add the result of the waves mixing to the vertex position… but I’ve found it’s more correct to subtract it (like in the Tessendorf paper): allow the steepness factor (that controls the sharpness of the wave) to work correctly.
But now I have another problem popping out if using tassellation and World Position Displacement: my shader affects the new vertex from tassellation, but moves these vertex in a strange, noisy way.
They seem to the displaced according to some short wavelenght wave and flattening to the highest position.
You can see that from a long range the mesh is ok… zooming in the tassellation begins to mess the plane…
Any ideas?
