motion blur in performer

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AnitaKishore (kishore++at++electrogig.com)
Tue, 26 Sep 1995 12:40:50 -0700

I have a problem in motion blur when I try doing it against a static
background. I loose the "vapour trails" of the moving object with each
accumulation because I think the remenants of the previous image of the
moving object is being wiped off by the current accumulation of the scene.
If I have no static part, then I get a nice moving geometry leaving behind
it a nice vapour trail. My set up is as follows:

scene graph looks like:

        pfScene
|
     --------------
| |
   pfDCS static scene
| background
   object to be
 motion blurred

In the pipe window configuration callback:

        pfOpenPWin(pw);
        drawmode(NORMALDRAW);
        subpixel(TRUE);
        acsize (16);
        pfInitGfx();
        acbuf (AC_CLEAR, 0.0);

In the motion blurred geometry node's post traversal DRAW callback:

        acbuf(AC_MULT, .88); // .88 controls the size of vapour trail
        acbuf (AC_ACCUMULATE, 1.0);
        acbuf (AC_RETURN, 1.0);

The object is translated to certain distance through the DCS.

With this setting the inside of the object is blurred, but it doesn't
have a trail. The call to acbuf (AC_ACCUMULATE, 1.0) destroys the previous
contents of the acbuf and hence the trail is lost.

Can somebody help me out??

Thanks for any help

-anita

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Anita Kishore
kishore++at++electrogig.com
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