Randy Crawford: |I'm trying to visualize a simple volume using OpenDX 4.1.3 on Linux |(Red Hat 7.1, XFree86 4.0.3), and a majority of my subvolumes are |not appearing. Is there a secret as to how the colormap indices |are allocated in Linux or XFree86 4.0? Is the Linux implementation |of OpenDX different from the standard in some way? Is there a way to |know what the colormap indices are so I can access them directly? ... |The volume is composed of perhaps 15 subvolumes of different colors. |Perhaps 3 of the subvolumes appear; the rest are black.
Sounds like you're doing software volume rendering, so your X server (XFree86) is just being used as a pixel blitter (this is independent of the OS you're using). I'm running XFree86 4.1.0 (on FreeBSD). Send me an example and I'll run it here on on an SGI at work to see if there's any difference. A couple thoughts: Set DXGAMMA to some number (e.g. "1") in your environment before invoking DX, and make sure no other DXGAMMA* variables are set. Display uses a gamma factor for rendering, with internal gamma defaults, overridable by the DXGAMMA* env vars. Gamma is used for volume rendering. Also, are any of your volumes coincident? I recall reading something about DX's volume renderer not supporting rendering of coincident volumes. Finally, what are your opacities set to? The color components set the "emissive" properties of the volume, while opacities components set the "absorptive" properties. If your front volumes are overly absorptive, that might explain things. |Oddly, the bisecting slice that is drawn by Gridded_3D_1var_notseries |often reveals subvolumes in that plane that are otherwise invisible. |But I don't know what this implies. This slice is rendered with polygon rendering instead of volume rendering. Totally different animal. It takes a fair amount of patience to get anything really useful from volume rendering. Much easier to set isosurface bands to interesting structural boundaries in your dataset, and render the isosurfaces using translucent polygon rendering. Then, if you prefer the volume look you can use a similar strategy to set interesting voxel bands to higher opacities, and volume render. Randy -- Randall Hopper [EMAIL PROTECTED]
