Le 24/07/2015 10:31, Matthias Kuhn a écrit :
Thank you for the hints. Please allow me one question here. I have
recently plaied with OpenGL for rendering and did let the GPU do CRS
transformation. I could not get it to work to my full satisfaction,
based on the fact that I only had float but no double precision.
Therefore e.g. CRS 21781 (in meters) already uses 6 figures for
meters, one more is still ok but when you zoom into cm resolution you
start to see the precision / rounding errors in rendering.
For reprojection I guess you had to also deal with precision of
coordinates. Did you use OpenGL features which are able to use double,
transform coordinates into an intermediate format before sending them
to the GPU or something totally different?
Hi Matthias,
Sorry for the late reply. For now Ice does not do anything specific to
prevent loss of precision of coordinates in rendering, so this is
another stone in Ice garden. However, I think that a fairly simple
workaround is to shift/scale coordinates before rendering (for instance
according to the data bouding box), eventually even change shift/scale
settings with respect to zoom level, so that to ensure a controlled
precision of coordinates in rendering. An example of software doing this
is CloudCompare, which is a very good points clouds visualization
software. If you load a point cloud with large coordinates, it will warn
you about possible precision loss and propose to shift/scale the
coordinates.
Hope that helps,
Regards,
Julien
--
Julien MICHEL
CNES - DCT/SI/AP
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