[vtkusers] Problem displaying actors with large coordinates values ?

[David E DeMarle]

I've seen the effect before. As I recall it is caused by lack of
precision in the GL library that VTK uses (24bits for X or something
to that effect). I am not aware of a good solution. Perhaps someone
else will chime in with one.

David E DeMarle
Kitware, Inc.
R&D Engineer
28 Corporate Drive
Clifton Park, NY 12065-8662
Phone: 518-371-3971 x109



On Mon, Jun 29, 2009 at 11:34 PM, pof<jd379252 at gmail.com> wrote:
> Dear vtk'ers,
>
> I need to display actors that are built from vtkPoints::New(VTK_DOUBLE) and
> that have large coordinate values (typically in the range 1e6 to 1e7, coming
> from Digital Elevation Model), although the scene extent (xmax-xmin,
> ymax-ymin, zmax-zmin) is in the order of (1e3, 1e3, 1e3).
>
> When displaying such objects in a scene, everything looks fine at first
> sight.
> However, as soon as some rotation and zooming are applied with the mouse
> action, the scene becomes less neat, and there are some random overlaps
> (i.e. it is changing as the viewpoint is changed) between actors.
>
> So far, the only way I found to get rid off these nasty artifacts is to
> perform a translation of the vtkPoints instance, such that its coordinates
> values become much smaller.
> However, I would really prefer to avoid such translation to save memory, as
> I need to keep the original data (i.e. untranslated data points).
>
> To solve this, I'm thinking about some possibilities, so far unsuccessful:
> - Perform the translation at the actor's level, but I have not found any
> method to do that.
> - Force the actor display to use 'double' reals as I guess it is presently
> using 'float' reals (note that I'm already using 'double' vtkPoints instead
> of 'float', though it hardly has any effect on the displayed artifacts)
>
> Does anybody has a clever idea or comment that could point me towards the
> right direction?
> Thanks,
> P.F.
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