--On Wednesday, June 14, 2000 3:42 PM -0400 "J. Lee Dixon"
<[EMAIL PROTECTED]> wrote:
> Is there a specific reason why you would not want to draw it during the
> postRender() function? At that time, everything else is drawn and you can
> force something to be drawn "in front" of everything else, like a
> heads-up-display.
If the graphics I want to draw can be drawn with Java3D immediate mode
commands, that will work fine (I suspect), but I can't use that to:
- draw a Java-3D scene graph in front of everything else
- efficiently draw a 2D scene into the window using something like Swing
Is there a way to have a J3D scene graph fragment, and just say "draw this
now"?
> This method is preferred (IMHO) since trying to put something on the front
> clipping plane is relying on floating point calculations, whereas drawing
> the object during the postRender() is more of a logical operation (much
> more predictable).
>
> Am I making sense? (no caffeine since 10:30am this morning....)
Yes, you are making sence.
The problem is, Java-3D does not allow arbitrary things to be done in those
hooks.
What I would love to see is to have Java-3D break it's scene graph
management and rendering out into utility functions, so that the "main
loop" that is illustrated in the discussion of the pre- and post-render
hooks effectively becomes a real loop I could change.
For example, I would love to be able to have a set of scene graph that I
render in sequence, interleaved with OpenGL commands. I would obviously
need to be able to tell Java3D that I've potentially blown away any
inter-frame state optimizations it makes, or tell it simply to re-set-up
some of it's state.
Why would I want to do this? Here's some simple examples (which are not
the only reasons I want this, but are ones):
- How about being able to create a set of cubes, each of which contains a
3D scene that is clipped to the boundaries of the cube. There is no way in
J3D (that I know of) to create user-defined clipping planes that clip
another part of the scene. But, if I could create a J3D graph for each of
those cubes, and then set up user-defined clipping planes before I render
each of these separate scene graphs, this would be easy.
- Lets say I want to create a dynamic set of textures that I manage myself
(ie. on my SGI O2s and Visual Workstation 320s, I can send a video stream
directly into a live texture). I can't use these in Java3D, but if I can
mix OpenGL and Java3D rendering, I could put the appropriate polygon in the
world.
Basically, there will always be examples of things I want to do that Java3D
can't do. If I can mix Java3D (even at a performance penalty that I'm
willing to pay) with the underlying graphics library, or mix Java3D scenes
in weird ways, I may be able to do these things. In a sense, I'd like to
be able to occasionally use J3D as a "OpenGL (or Direct3D) scene graph" :-)
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