[vtkusers] seams between transparent surfaces

[Paul Hamill]

Cory -

I added these calls:
ren.UseDepthPeelingOn()  # ren is vtkRenderer
win.SetAlphaBitPlanes(1) # win is vtkRenderWindow

This did get rid of the seam effect, but produced unwanted side effects: the 
planes have different colors, and are opaque at some view angles instead of 
transparent. A screenshot showing this is attached.

Maybe my graphics card is incompatible with VTK's depth peeling.

Thanks -
Paul

Cory Quammen wrote:
> Paul,
> 
> When drawing transparent geometry, geometry needs to be sorted in
> depth order, or you need to use depth peeling which in a sense does
> the depth sorting for you. Fortunately, VTK implements depth peeling.
> In your vtkRenderer, call UseDepthPeelingOn(). This ought to eliminate
> the seams, assuming your graphics hardware supports VTK's
> implementation of depth peeling.
> 
> Cory
> 
> On Fri, Dec 5, 2008 at 2:11 PM, Paul Hamill <paulh at txcorp.com> wrote:
>> Hi -
>>
>> We're using VTK called from Python to create climate data visualizations. A
>> structured mesh is divided into sub-meshes or "tiles" to support
>> parallelization. We are seeing "seams" between meshes when they have alpha
>> transparency. The attached screenshot is a simplified example of this. There
>> are two adjacent pairs of planar surfaces. When viewed from some angles a
>> polygonal shape appears where the surfaces meet. (Here it looks like a wide
>> line running across the middle of the front plane.) The Python code that
>> generates this image is also attached. Run "python exSeamProblem.py" to
>> create this image and rotate it to see the seam.
>>
>> Any advice or information about this problem is much appreciated.
>>
>> Thanks -
>> Paul
>> --
>>   Paul Hamill
>>   Tech-X Corp
>>
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> 
> 
> 


-- 
    Paul Hamill
    Tech-X Corp
    paulh at txcorp.com
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