First of all, direct volume rendering is only supported in software with an orthographic camera. If you request h/w rendering, you'll just get the bounding box rendered. Chikai Ohazama of SGI did write a direct volume render for DX using SGI's OpenGL Volumizer package about 2-1/2 years ago.
Secondly, you really can't combine red and green effectively. This is independent of DX. It has to do with rules for color mixing. If you are rendering two volumes defined on the same vertices or cell centers, then this is probably the source of your problem. Depending on your opacity map (transfer function), the apparent density is to high to permit "light" to pass through. You should consider adjusting the color and opacity maps to avoid this problem, using Slab and/or Include to eliminate portions of each of the volumes You should look at some of the DX documentation that discusses how it does volume rendering, e.g., http://www.research.ibm.com/dx/docs/legacyhtml/pages/usrgu060.htm#HDRVOLRND http://www.research.ibm.com/dx/docs/legacyhtml/pages/usrgu025.htm#HDROPACOM http://www.research.ibm.com/dx/docs/legacyhtml/pages/refgu048.htm http://www.research.ibm.com/dx/docs/legacyhtml/pages/progu077.htm#HDRRENDMDL http://www.research.ibm.com/dx/docs/legacyhtml/pages/usrgu040.htm#HDRGLOPT Having said all of that, there are some methods of combining multiple volume-rendered fields in DX. A good example is the work of Pat McCormick and his colleagues at LANL done about four years ago. See http://www.acl.lanl.gov/viz/papers/wildfire/sgexampl.html for more information. Christian Soeller <[EMAIL PROTECTED]>@opendx.watson.ibm.com on 04/22/2001 04:23:47 PM Please respond to [email protected] Sent by: [EMAIL PROTECTED] To: "[email protected]" <[email protected]> cc: Subject: [opendx-users] display of two volume rendered data sets I have tried to display two volume rendered data sets simultaneously with the image module. I coloured one using a red the other using a green colour table and would like to overlay those to test for protein colocalization. Each data set individually displays fine when wired into the image module. However, when collecting both data sets into image simultaneously, the resulting image is just black. This happens in software rendering mode. Hardware rendering mode doesn't seem to work properly anyway for volume rendering on my box. platform: Debian woody with NVIDIA Geforce2 + Nvidia Xfree86-4 drivers dx version: debian package dx-4.1.0-5 Any hints would be appreciated. Thanks, Christian -- Christian Soeller [EMAIL PROTECTED] x2770 Dept. of Physiology U. Auckland School of Medicine Auckland New Zealand
