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View Full Version : Volumetric Fog and displaying Probability Densities



nethtrick
08-31-2004, 10:33 AM
I've been experimenting with visualization of probability densities (basically, electron clouds). For the time being, I have been using a vast array of varyingly transluscent points in combination with glPointSize() to get the desired 3-D clouding effect. However, this gets very laggy very quickly. Does anyone have any suggestions on a better (and faster) way to display volumetric data in 3D? I have tried using custom fog coordinates, but for some reason glFogCoordf() is having trouble compiling for me.
(see my other post)
http://www.opengl.org/discussion_boards/cgi_directory/ultimatebb.cgi?ubb=get_topic;f=9;t=000306

On the other hand, I'm not sure if glFogCoords work the way I would need them to.
Perhaps volumetric lighting? If anyone has experience with this, let me know. Thanks.

ZbuffeR
08-31-2004, 11:22 AM
For volumetric rendering see :
http://www.opengl.org/discussion_boards/cgi_directory/ultimatebb.cgi?ubb=get_topic;f=2;t=017063

nethtrick
09-02-2004, 02:22 PM
I will check it out. Thanks for pointing me in the right direction.

dorbie
09-03-2004, 11:19 AM
Yep fog is definitely wrong. The point method you found slow is usually called splatting.

A common technique (described in the links) is to load your 3D data set into a 3D texture (optionally with alpha) and sample the ray paths through the volume with textured slices oriented in eye space.

This should give you the kind of results you need but can be slow due to the enormous demands the ray path integration makes on hardware texture and blend operations.