[vtkusers] Fwd: vtkOpenGLProjectedTetrahedraMapper vs vtkUnstructuredGridVolumeRayCastMapper

[Artem Babayan]

Thank you for your reply

> Are you calling setScalarOpacityUnitDistance? Perhaps this could be
> part of the problem.

No, I use 'SetScalarOpacity' method passing vtkPiecewiseFunction . I
think 'setScalarOpacityUnitDistance' should be used for
'normalization' of the opacity -- to achieve the same opacity for
domains of different size by adjusting a single coefficient.



>  Is the only thing
> being changed the volume mapper?

Yes -- I set it up the visualization parameters, including mapper, via
my own input file. And in this case only mapper was changed.

My guess is, that vtkOpenGLProjectedTetrahedraMapper and
OpenGLHAVSVolumeMapper use fixed-point arithmetics, so cannot
distinguish values below the certain value.

>
> On 9 June 2010 15:21, Artem Babayan <artem.paraview at googlemail.com> wrote:
>> Hello,
>>
>> I have the following situation:
>>
>> 1) 3D scalar field defined on non-uniform Cartesian grid is read from
>> .vtk  file with vtkStructuredPointsReader
>> 2) Read data then fed to to vtkDataSetTriangleFilter
>> 3) Color and opacity map are set.
>> 4) 3D filed is visualised using vtkUnstructuredGridVolumeRayCastMapper
>> or vtkOpenGLProjectedTetrahedraMapper or OpenGLHAVSVolumeMapper
>>
>> As a result -- I've got 3 completely different pictures (attached 1st
>> for  vtkUnstructuredGridVolumeRayCastMapper, 2nd for
>> vtkOpenGLProjectedTetrahedraMapper and 3rd for vtkOpenGLHAVSVolumeMapper)
>> -- ignore the blocks as they are irrelevant here. Why is it so and
>> which one is correct? It looks like at least vtkOpenGLHAVSVolumeMapper
>> cannot 'see'
>> values below certain level.
>>
>> If it is of any help -- the data range is from 1e-25 to 14.0 and the
>> non-uniform Cartesian grid is non-uniform in z-direction only.
>> The grid size are the following: dx==dy==25 , dz[] = {0, 4, 12, 30,
>> 70, 150, 290, 670, 1020}
>>
>> Best wishes
>> Artem
>>
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>