[vtkusers] Stretch/deform surface

[Marius Erdt]

Hi,

I'd like to manually deform a polyData surface, i.e. I set two mouse 
positions and I want a part of the surface to be stretched in the 
direction given by the vector between the points (just like what is 
possible in CAD programs).

I've tried to use the vtkThinPlateSplineTransform on the surface, but 
this has a very global effect on the model. That means, the whole 
surface is translated in the given direction, instead of just a small 
neighborhood. I'm not sure if this is the right approach at all, since 
the only parameter to set on the underlying function is the sigma and as 
far as I have tried, it does not change much.

Another approach would be to draw a sphere and collect all points of the 
surface that lie inside the sphere with vtkSelectEnclosedPoints. As a 
result, it is known for every point of the surface whether it lies 
inside or outside of the sphere. However, the problem remains how to 
apply a transform only on the labeled points. The 
vtkWeightedTransformFilter should do something like that, but I'm not 
sure how to weight the input transform for the surface points.

Does anyone have an idea what approach seems to be the most promising one?

Thanks for help,
Marius