Hi Clement, On 5 March 2012 03:04, <[email protected]> wrote: > My program was using coin3D for volume rendering before. Now it is > replaced with osg, but I still want the existing machine is able to run osg > version. Last time you mentioned it is possible to implement a crude 3D > volume rendering based on 2D textures. Can you tell me more in details how > to do? Do you mean the current osg doesn't have this feature? Is it > required to modify the source code and recompile again? Thanks.
I am not about to complicate osgVolume with backwards compatibility to hardware that can't do volume rendering properly so this will be something you'll have to implement at your end. The way to do volume rendering with 2D textures is very limited but possible - you need to create a stack of 2D images that build up the volume, and then render a each of images as a 2D texture assigned to an axis aligned quad, building up the image from back to front. To handle viewing from all angles you'll need to create three sets of 2D images, one for each axis so as you rotate around the volume you can select the most closely aligned axis. This will use more memory than using proper 3D textures, and it'll be far less flexible as you won't be able to compute normal on the GPU or do any decent shader operations. The final product of you work will be compatibility but on as far as the lowest common denominator - i..e. really crude low res volumes. Alternatively you could spend a small amount of money on a graphics card for your systems that is capable of doing volume rendering. Even a low end ATI or NVidia card will be able to do volume rendering - it'll be slow, but still way faster than the Intel graphics and way higher visual quality. You'll save lots of time - you'll only need to save a couple of hours work to break even on the purchase of the graphics card - in fact I have little doubt that you've already wasted far more time and money trying to get by with crappy hardware that isn't up to the job. As for Coin3D doing it, well it's implementation of volume rendering is not too advanced - it's stuck at the lowest common denominator level that you really should be expecting to exceed these days. Robert. _______________________________________________ osg-users mailing list [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
