[osg-users] osgText precision issue

beelzebob999-osg at yahoo.com beelzebob999-osg at yahoo.com
Sat Sep 8 10:49:27 PDT 2007

Years ago, we wrote an earth-viewer program in which
we had a requirement that we had to be able to zoom
all the way from space, down to an item the size of a
quarter and smaller, smoothly.  Your images look like
an issue we had at the time, which was a floating
point precision problem.  The openGL stacks we had
apparently could only use floats, and did all matrix
multiplication as floats (even if the matrices we
passed in were doubles).  The fix was to maintain our
own matrix stack (of doubles) and do all matrix
multiplication ourselves, and load the finished matrix
into GL on each frame.  

I don't know if it's possible to configure OpenGL now
to use doubles for its matrix stacks instead of
floats, but, if so, I bet that would fix your problem.

--- sherman wilcox <wilcox.sherman at gmail.com> wrote:

> I'm having a bit of trouble with mangled text if I
> zoom in to close.
> This text is on an osgDem generated ellispoid. In
> the attached
> screenshots, the text appears correctly in
> text2.jpg. However, in
> text3.jpg you'll see the problem. This only occurs
> if I zoom in really
> close to the text. If I back off the camera a bit,
> the text reverts
> back to the correct state.
> My questions are:
> 1) What's causing this?
> 2) How best to address the issue?
> > _______________________________________________
> osg-users mailing list
> osg-users at lists.openscenegraph.org

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