[vtkusers] vtkOpenGLProjectedTetrahedraMapper opacity

[Artem Babayan]

Hi,

I am visualizing the 3D scalar field using
vtkOpenGLProjectedTetrahedraMapper and
vtkUnstructuredGridVolumeRayCastMapper . For some reason, the faster
vtkOpenGLProjectedTetrahedraMapper incorrectly (?) or at least
differently handles opacity settings.

The values in vtkPiecewiseFunction are:      (0 ,  -1),   ( 0,  1) ,
 (1,  35) so I would expect areas where scalar values are 0 to be
transparent. This is true with vtkUnstructuredGridVolumeRayCastMapper
but not with vtkOpenGLProjectedTetrahedraMapper -- see attached
pictures.

Is it a feature or a bug? If this is a feature, what opacity values I
should use to get full transparency?

Best wishes
Artem
-------------- next part --------------
A non-text attachment was scrubbed...
Name: picGLProjected.png
Type: image/png
Size: 46664 bytes
Desc: not available
URL: <http://www.vtk.org/pipermail/vtkusers/attachments/20101021/b7c6bdf2/attachment.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: picVolumeRay.png
Type: image/png
Size: 27984 bytes
Desc: not available
URL: <http://www.vtk.org/pipermail/vtkusers/attachments/20101021/b7c6bdf2/attachment-0001.png>