[vtkusers] Changing UserMatrix in Vol. rendering

[Asad A. Abu-Tarif]

Hi,
I was vol. rendering a vtkStructuredPoints using the Ray Casting method and I wanted to move the actor (represented as vtkVolume) using the (SetUserMatrix) method and then render again. However, I get the following error when I do that:

ERROR: In D:\vtk31\graphics\vtkViewRays.cxx, line 126
vtkViewRays (0x0745E0c0): View Rays has a 0 area, must SetSize() to area > 0

This only happens when I render, then change the actor transformation using the SetUserMatrix, and then try to render again. However, if I set the user matrix before I render, no error occurs. My problem is that I'm performing registration and I need to display the vtkVolume object with multiple consecutive transformations.

Any help will be greately appreciated.

Thanks
Asad

==============================================
The code that generates the error:
renderer1->AddVolume(MyVolume);
// render. 
// do some calculations and wait for user input.
MyVolume->SetUserMatrix(MyMatrix)
// render again. (here is were I get the error).
================================================

No error occurs when I don't render the first time (do the calculation and just render the volume after the transformation).

 
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