[vtkusers] Use depth map from vtkShadowMapBakerPass

[Ken Martin]

Not sure if this helps (or is your issue) but the depth values are post
light-camera perspective transform. To get them back into world coordinates
you have to apply the inverse of that transform (or something simpler if
you just want the world coordinate distance). It is a non-linear mapping.
If you google zbuffer to world there are usually a number of hits that talk
about this process. To do it you need the  light-camera clipping range from
the original matrix (around line 619 in the shadow  map baker pass)

Thanks
Ken



On Thu, Jun 9, 2016 at 7:05 AM, Maximilian Dankbar <indienator at gmx.de>
wrote:

> Hi everyone,
>
> I try to use the depth maps generated by vtkShadowMapBakerPass to
> determine which objects are occluded by other objects.  To do that I
> download the texture to an unsigned int array.
>
> However I can not figure out how to interpret the values within the map.
> Normalizing with the clipping range values of the corresponding light
> camera only works for one camera position. In that case the direction of
> projection of the camera is (0, 1, 0). In all other cases that I tested the
> near clipping range is far too low and the far clipping range probably too
> high.
>
> Is there any other way to normalize the depth values?
>
> Thank you in advance for your help!
> Max
>
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-- 
Ken Martin PhD
Chairman & CFO
Kitware Inc.
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