I can't think of any reason why this should be the case. It might be
a bug.
--
Kevin Rushforth
Java 3D Team
Sun Microsystems
[EMAIL PROTECTED]
>Date: Sat, 18 Sep 1999 22:24:29 -0700
>From: Jon Barrilleaux <[EMAIL PROTECTED]>
>Subject: [JAVA3D] what is inside Billboard?
>To: [EMAIL PROTECTED]
>
>I'm performing a pseudo-overlay operation that involves scaling down
>an object and moving it very close to the display. This involves
>detecting changes in view geometry and then updating the overlay
>object geometry.
>
>Now we all know that Java 3D has problems doing such operations
>because the change detection occurs in one scene graph "cycle" and any
>resulting programmatic update won't be seen until the next "cycle"
>(i.e. the operation always appears to be one cycle behind). However,
>I've noticed something odd going on when I use a billboard together
>with my pseudo-overlay object. The billboard appears to "draw" its
>target object closer to the display than my object (which is only
>about 0.25 units from the eye). Then, about .1 or .2 seconds later
>(i.e. much longer than a frame cycle) my object appears in front of
>the billboard one like it should.
>
>This all seems most odd. I know this descriptionis a bit cryptic but
>I'm really curious as to what is going on inside of Billboard? I'm
>certain of the geometries involved, and my object is always in front
>of the billboard one. How could the Billboard possibly "draw"
>anything in front of an object that is closer to the display? Is it
>doing some sort of immediate mode rendering (I don't see why it should
>but that is what appears to be happening)? Why the appreciable delay
>between the biillboard doing its "drawing" and my object appearing?
>When my object interacts with non-Billboard objects everything is as
>it should be (other than looking crappy because it is always one cycle
>behind).
>
>Any clues? Is this a bug?
>
>--jon
>____________________ Peculiar Technologies ____________________
>Jon Barrilleaux 3800 Lake Shore Ave. Purveyors of
>[EMAIL PROTECTED] Oakland, CA 94610 Alternate Reality
>510.444.4370 voc Augmented Simulation
>510.444.0231 fax www.augsim.com and 3D Solutions
>
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