Hi, I haven't done a direct comparison on performance, but the only real overhead at tile loading is a small step in deciding which images to load. There are more files read from disk as the images are not inline which is probably a little slower that reading a single file but I don't think it will effect performance much.
>From my experience, the biggest hit is the 'unbounded' number of textures >required to render a single tile. Using the standard approach only a single >texture exists for each tile. Using optional layers you could theoretically >have an unlimited number of textures to render to each tile. In theory you >could even run out of texture units / samplers for each tile (though in >practice you need a lot of optional layers for this). Accessing and blending multiple textures will obviously be slower than only using one, though I havent noticed much of a performance difference in practice when I turn on or off a bunch of optional layers. The other side effect of this is complicating the management of the shaders used to render the tile (assuming you are not using fixed function). To get good performance on both ATI and Nvidia cards I ended up creating a separate shader for all possible number of active optional layers and switching between them at run time. this works much better than my original approach which used dynamic branching in a single shader. Cheers, Brad -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Torben Dannhauer Sent: Wednesday, 6 July 2011 8:26 PM To: [email protected] Subject: Re: [osg-users] [vpb] Questions regarding setname, optional layers and layer inheritance Hi Brad, I realized that I missed a very central question regarding optional layers: How to they affect the rendering performance? Of course it takes some computation time to merge all different layers, but have you some hints how the performance is im comparison to a native database with all data directly integrated? Thank you! Cheers, Torben ------------------ Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=41191#41191 _______________________________________________ osg-users mailing list [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org ------------------------------------------------------------------------- DISCLAIMER: This e-mail transmission and any documents, files and previous e-mail messages attached to it are private and confidential. They may contain proprietary or copyright material or information that is subject to legal professional privilege. They are for the use of the intended recipient only. Any unauthorised viewing, use, disclosure, copying, alteration, storage or distribution of, or reliance on, this message is strictly prohibited. No part may be reproduced, adapted or transmitted without the written permission of the owner. If you have received this transmission in error, or are not an authorised recipient, please immediately notify the sender by return email, delete this message and all copies from your e-mail system, and destroy any printed copies. Receipt by anyone other than the intended recipient should not be deemed a waiver of any privilege or protection. Thales Australia does not warrant or represent that this e-mail or any documents, files and previous e-mail messages attached are error or virus free. ------------------------------------------------------------------------- _______________________________________________ osg-users mailing list [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
