Enviromental mapping could use a pre-rendered texture (like a 50% sky/50% ground horizon type of image), which gives decent results for simple things (clouds reflecting off water or shiny objects)... I've done this quite a bit in D3D, playing with MS's environmental mapping samples in the SDK (no flames please, I'm all J3D now).
Or, if you DO choose to render the 6 views off-screen, they could be done at very low resolution (32x32 or 64x64 perhaps?) which would of course be a penalty hit, but for demo purposes, it would be a very cool looking result... and also you aren't adding any additional overhead for behaviors and such, so it might not be that much of a hit. Would be interesting to see how much performance drain it really causes.
Scott
-----Original Message-----
From: Yazel, David J. [mailto:[EMAIL PROTECTED]]
Sent: Friday, May 03, 2002 8:59 AM
To: [EMAIL PROTECTED]
Subject: Re: [JAVA3D] Demo for TextureCubeMap posted on Java3d
Discussion List
Thanks for the demo!
I have never understood how spherical and cube environment mapping could be
used in anything other than the very smallest demo since it requires
multiple offscreen rendering to get the surrounding textures. Your demo
just creates the surrounding textures and fills them with colors, which is
good as an example. But for for this type of mapping to have value you
would need to render the scene from the vantage point of the mapped object 6
times into an offscreen buffer and then turn them into textures for the
env-map. I don't understand how this can be done with any kind of speed.
For example, if an application runs at 100 frames a second normally and you
wanted to create a cube map for a shiny box that drifting through your
scene, then you would need to render the scene 7 times, 6 to build the env
map, and then 1 to draw the whole scene. Not counting the time to move
those textures back and forth your fps would run something like 18 fps.
That seems like extremely high pice to pay for a relatively unimportant
visual improvement.
I have seen examples where people use environment maps to show the
reflection of the sky and terrain in the water.. but if that is spherical
mapping then you would need to recompute it every frame. Cube mapping would
only have to be computed if the scene changes, but at least it does not have
to be recomputed if the orientation of the camera changes. Another trick is
not to sue environment mapping at all, but render the scene without the
water, and then texture map that back into the water, which requires
complete scene redraws.
Seems like all these techniques are horridly impractical unless you have an
extremely simple scene. Would people really put up with (at the very least)
cutting their framerates in half so they can see a reflecton?
===========================================================================
To unsubscribe, send email to [EMAIL PROTECTED] and include in the body
of the message "signoff JAVA3D-INTEREST". For general help, send email to
[EMAIL PROTECTED] and include in the body of the message "help".
