I'm working on a similar problem: rendering a large vector field as several arrows, all with different positions and orientations. If I multiparent the Geometry to several PAT nodes, the cull time cost is quite high. I'm looking at adding support for ARB_draw_instanced to reduce both the cull and draw time. Right now, I'm attacking it as a new PrimitiveSet, "DrawArraysInstanced", which works essentially like the DrawArrays PrimitiveSet but emits a glDrawArraysInstancedARB() command to effect the rendering. Making some progress, but it's not there yet (and I'll also have to add support for glDrawElementsInstancedARB). I expect I'll contribute this back to OSG if I get it running. Paul Martz Skew Matrix Software LLC http://www.skew-matrix.com <http://www.skew-matrix.com/> +1 303 859 9466
_____ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of David Spilling Sent: Friday, November 28, 2008 9:22 AM To: OpenSceneGraph Users Subject: [osg-users] Performance query : Drawing lots of "instances" of avertex array Dear All, I have a geometry with a simple heightfield type vertex array; I'm also using VBO. I want to repeat that VBO in quite a lot of places. The heighfield can be considered as a terrain "tile" (e.g. 100m x 100m) , with which I want to tile a much larger area (e.g. >1km x 1km). The method I have so far implemented is to have the following scenegraph: Group / | \ / | \ G1 G2 G3 \ | / \ | / Tile with VBO and vertex shader where G1..Gn are simple groups which set a tile_offset uniform. The vertex shader on the tile uses the tile_offset to modify the vertexes for each tile. This all works OK. However, I am concerned that this is not the best route for high performance when the tile count is quite high. e.g. is it better for G1...Gn to be matrix transforms (presumably not, although an easy thing for me to test). Is this a good example for the geometry instancing extensions? So, does anybody have any good advice for doing this kind of thing in a better way within OSG? Pointers or examples (or even hints) would be appreciated... Thanks in advance, David
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