I was interested in drawing less than all of the data in DrawElements as I stated in this mailing list thread: http://lists.openscenegraph.org/pipermail/osg-users-openscenegraph.org/2013-July/063950.html
Looking at DrawElements* in PrimitiveSet.cpp, they seem to be hardwired to draw all the data. I added a _count variable like in DrawArrays to let the user draw only a subset of the data. I also added a _countDefined flag to be set when the user actually defines a count. If it's not set, the old behavior of drawing all the data is used. I'm not sure if this is the best solution, but I don't see another way to do it without changing the API because, unlike DrawArrays, DrawElements can be initialized with no count specified. However it ends up being implemented, this seems like good functionality to have. Not allowing a count to be specified removes access to an OpenGL feature that should be exposed. -- Terry Welsh www.reallyslick.com
PrimitiveSet.tar.gz
Description: GNU Zip compressed data
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