From: Paolo Farinelli (paolo++at++sgi.com)
Date: 06/21/2002 19:57:55
Hi Ken,
please excuse my late (and brief) reply.
From man pfClipTexture:
On systems without hardware support for cliptextures,
pfClipTextures are
implemented through software emulation. The software emulation
implementation manages a list of independent texture objects: one
mipmapped texture stores all pyramid levels of cliptexture (up to and
including the first level of size clipsize), and other (non-mipmapped)
textures store the data associated with each roaming level. Performer
will automatically compute and store texture coordinate bounds for each
pfGeoSet that is to be rendered with a cliptexture. Then, on each
frame,
depending on the size and position of texcoord bounds with respect to
current clipcenter position, the texture associated with the highest
resolution level which completely covers pfGeoSet's geometry (in
texture
space) will be used for rendering the pfGeoSet. Note that this is
achieved by creating specific pfDrawBins on each pfChannel for each one
of the roaming levels of each pfClipTexture, and by inserting each
cliptextured pfGeoSet into a sub-bin of the pfGeoSet's original DrawBin
and the DrawBin associated with the selected cliptexture level.
Take a look at the clipdemo sample program in
/usr/share/Performer/src/sample/C++/
for an example of how to set up an emulated cliptexture.
Regards,
Paolo
Ken Sewell wrote:
>Is there a detailed explanation of how Performer 2.5 does its software
>cliptexture emulation and what limitations we need to keep in mind when
>using it? I've been encountering some problems in applying a cliptexture
>to a piece of terrain in geocentric space. Regular textures apply fine,
>and clipfly displays my cliptexture correctly. I wondering if the
>orientation of my terrain can affect the cliptexture emulation.
>
>Thanks.
>
>Ken Sewell Defense Research Associates
>Project Engineer 3915 Germany Lane, Suite 102
>937-431-1644 Beavercreek, Ohio 45431-1608
>sewell++at++dramail.com
>
>
-- Paolo Farinelli paolo++at++sgi.com Member of Technical Staff, OpenGL Performer 1-650-933-1808 Silicon Graphics 1600 Amphitheatre Pkwy, Mountain View, CA 94043
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