[vtkusers] UTM coordinates, double precision, structured and unstructured grids

[David E DeMarle]

This is opengl precision. The solutions I've seen subtract to single
precision as you've done. Newer cards, or alternatively specially
configured mesa, are potential alternatives.
On Jul 11, 2012 6:50 PM, "Richard R McDonald" <rmcd at usgs.gov> wrote:

> Hello,
>
> We have an application that provides pre- and post- processing
> capabilities for computational models of flow and sediment transport in
> Rivers.  The application is built with Qt and VTK.  We use both structured
> and unstructured grids.  The grid x,y locations, stored in vtkPoints and
> set to datatype double, are specified in UTM coordinates. When zooming in
> close and rotating the the grid, the point locations jump around as if
> truncated to single precision.  Using the same data sets with a subtracted
> offset to bring the x,y locations down to single precision eliminates the
> problem.  Can anyone lend some insight as to why this might be happening?
> Is there a truncation issue in VTK or is it a product of the graphics
> board?  Any help would be greatly appreciated.
>
> Thank you,
> Rich McDonald
> Research Hydrologist
> USGS Geomorphology and Sediment Transport Laboratory
> 4620 Technology Drive, Suite 400
> Golden, CO 80403
> 303 278 7952
> rmcd at usgs.gov
>
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