[vtkusers] Z-Scaling in VTK

[Bruno da Silva de Oliveira]

Hi all,

I'm working with meshes that represent petroleum reservoirs. One of the 
characteristics of this type of model is that the X and Y dimensions are 
orders of magnitude greater than the Z dimensions (petroleum reservoirs 
are several kilometers wide, but few meters deep). To visualize this 
type of model, we employ z-scale, or vertical exaggeration, which 
consists in scaling the model along the Z axis.

I understand this can be achieved in VTK by setting the transformation 
of each actor, but one problem that I see with this approach is that 
other components of the visualization don't know about this. For 
instance, a vtkImplicitPlaneWidget doesn't know about the scaling along 
the Z-Axis, so the plane it returns is wrong regarding the world 
geometry. I know that you can apply the inverse of the scaling to get 
the correct plane, but I would like to know if another solution is possible.

I guess a perfect solution would be to set some kind of transform that 
is applied to the render, that scales all the objects in the world. This 
way, all the other components of the visualization would just work. Is 
this already implemented somewhere that I missed? Otherwise, how can I 
extend vtk to achieve this? Looking quickly at the code, one could add a 
WorldTransform matrix to the vtkViewport class and update all its 
functions that deal with world coordinates to take in account this new 
matrix, and also update the vtkRenderer class to apply this matrix 
before rendering the actors. Am I correct?

I'm using VTK 4.2 btw.

Thanks in advance,

-- 
Bruno da Silva de Oliveira
bruno at esss.com.br
ESSS - Engineering Simulation and Scientific Software
http://www.esss.com.br