Doug Twilleager wrote:
>
> This is a pretty good synopsis of the overall features of the different
> collision alternatives. I have a couple of comments on this. I'm sending
> this to the interest list because some of the comments relate to behaviors
> in general.
Great, thanks. I pull these in and put up another update later this
evening local time.
> Part of the disconnect here is that behaviors should be thought
> of as completely asynchronous from the rendering.
Is it a safe assumption to say that a new round of evaluation of the
triggers is the start of each frame? That is, we have to know when to
take another pass through the spatial tree to execute a behaviour. For
many of these, they are triggered by viewpoint information - visibility
behaviours for example.
A way I like to think of this is that we have two completely separate
threads (perhaps distributed across two machines to really make a
distinct break) one for rendering and one for behaviours. Each is
running as fast as possible. As soon as it finished it's current pass
through the "rendered" code it will immediately head to the top and
start a new pass. If the behaviours were to operate completely
independently of the pixel rendering, there would never be any sync. We
need to feed something back about where the current viewpoint in the
scene is. Now, if the start of the "top" of the behaviour rendering and
pixel rendering do not occur at exactly the same time, then we could end
up with nastiness with the viewpoint position moving while we are
halfway down the spatial tree. Oddness results.
So, in order to keep sanity, the behaviour renderer does not operate
unbounded like the pixel renderer. Instead it makes one pass and then
stops. It makes the next pass at the point where the pixel renderer
starts at the top of it's "tree" and updates view information allows the
behaviour renderer to make another pass.
--
Justin Couch Author, Java Hacker
http://www.vlc.com.au/~justin/ Java 3D FAQ Maintainer
http://www.j3d.org/ J3D.org The Java 3D Community Site
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Neither man nor woman is the measure of all things. Every organism
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- Greg Bear, Slant
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