looking thru a filter len

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Charlie H. Chang (a00chc00++at++nchc.gov.tw)
Wed, 03 Dec 1997 10:21:09 +0800


Hi,

I have asked this question before but didn't get what we want...
Our application has 8 channels, one of them will have a
yellow(red, green and black) color filtering len.

  (1) Someone suggested using glColorMask which will turn off
        R,G,B color bit(s), this result doesn't mimic the filtering
effect.
  (2) I tried to draw transparent polygon in front of the view but
       then some other channels will see this polygon as well, since
       four of the channels have the same view position.
  (3) I also tried "glPixelTransfer*" and did some color scale effect
        in channel drawing callback. This one seems ok, but the color
        of sky didn't change, which is OK because I can change ESky.
        However, all other channels were affected.

So my question is: is there any way I can do "glPixelTransfer*"
to one channel without discoloring other channels? Or there is
other better way to do this task?

The following is the code segment in my drawing callback:

   pfPushState();
   glPushMatrix();
   glMatrixMode(GL_COLOR);
   glPixelTransferi(GL_RED_SCALE, 2.0);

   pfCleanChan(chan);
   pfDraw();

   glPopMatrix();
   pfPopState();
   ....

--
Charlie H. Chang                E-mail: a00chc00++at++nchc.gov.tw
Voice: 886-3-5776085x209        Fax: 886-3-5773620
Media & Visualization Lab, National Center for High-performance
Computing

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