I didn't want to get on another soapbox this morning. I implied one with color with my first response. The second is that I agree with Chris. What you also can gain is the interactivity with the h/w rendering. Doing multiple isosurfaces of the two fields with complementary colors but also opacity mapped can be quite effective. The strategy taken by the LANL group for the wildfire visualization worked well, but it was expensive. They had a very large SGI machine to throw at the problem. In addition, creating transfer functions for volume rendering in general is considered difficult, and is still an open research area (e.g., an entertaining panel at the Vis2000 conference did a nice summary of the open questions, which will also be published in an upcoming IEEE Computer Graphics and Applications issue). This problem is further compounded by the less than intuitive mechanics that DX provides on such matters. However, in my opinion, the value of direct volume rendering for many data sets has yet to be proven. But there are people in the visualization community who will disagree with this point. Data sets with clear (physical) structure such as those derived from medical tomographic scanners lend themselves well. But others with more amorphous structure, particularly when noisy or defined on non-regular or unstructured grids, have not.
The links I cited will point you to the parts of the DX documentation that Chris cites. Chris Pelkie <[EMAIL PROTECTED]>@opendx.watson.ibm.com on 04/23/2001 07:24:41 AM Please respond to [email protected] Sent by: [EMAIL PROTECTED] To: [email protected] cc: Subject: Re: [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. > The documentation clearly (though obscurely) states that this is the case. You cannot render coincident volumes in DX, never have been able to on any platform. I think it's in the discussion of "components", specifically, colors and opacities in the User's Guide. Try Lloyd's links for other ideas, or use Isosurfaces which usually make a more comprehensible object and support Perspective rendering which helps enormously in my opinion for depth relationship perception. Chris Pelkie Vice President/Scientific Visualization Producer Conceptual Reality Presentations, Inc. 30 West Meadow Drive Ithaca, NY 14850 [EMAIL PROTECTED]
