Re: Transparency

New Message Reply Date view Thread view Subject view Author view

Jim Helman (jimh++at++surreal)
Tue, 22 Feb 94 10:35:04 -0800

By default, Performer draws all transparent geosets and
billboards (which are usually transparent) last. The
rendering order is less important when using multisample
transparency (msalpha == screendoor) than when using
blendfunction. But with blended alpha, you pick up the
color of the last thing drawn behind the partially
transparent object, which is often not the correct
backdrop. Fortunately, msalpha is our default on Reality
Engine. The downside is fewer alpha levels.

Note that node draw callbacks disable the draw-last feature
since the geometry in the subgraph rooted at that node must
be drawn within the scope of its pre/post draw callbacks.

If anyone has a need for better sorting, e.g. someone needs
lots of blended alpha billboards, they should contact us.
We have ways.

rgds,

-jim helman

jimh++at++surreal.asd.sgi.com
415/390-1151

  From: Bernd Froehlich <bernd++at++viswiz.gmd.de>
  Subject: Transparency
  To: info-performer++at++sgi.sgi.com
  Date: Tue, 22 Feb 94 18:18:09 MET
   
   
  Hello,
   
  how is transparency realized in Performer?
  In GL one has to render the opaque polygons first, then
  the transparent ones in decreasing order of distance from
  the eyepoint. Sorting is usually too expensive, so
  just drawing the opaque polygons first and the
  transparent ones last is ok for most cases.
  Is this supported in Performer and how?
   
  Thanks
   
  --Bernd
   
  bernd++at++viswiz.gmd.de
   
   
   

New Message Reply Date view Thread view Subject view Author view

This archive was generated by hypermail 2.0b2 on Mon Aug 10 1998 - 17:50:11 PDT

This message has been cleansed for anti-spam protection. Replace '++at++' in any mail addresses with the '@' symbol.