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>Date: Thu, 29 Nov 2001 20:11:21 -0500
>From: David Yazel <[EMAIL PROTECTED]>
>Subject: Re: [JAVA3D] Where to find "perf_guide.txt"?
>To: [EMAIL PROTECTED]
>
>In relation to the speedups for drawing 2D on top of the 3d Canvas:
>
>1.  Has anyone compared texture mapped 3d objects to the new features?

Since J3DGraphics2D use mixed mode or PureImmediate rendering,
the flush() routine will pass the size of rectangular dirty region
down as texture mapped (by default -Dj3d.g2ddrawpixel=false under window)
every frame. So it would be slower if the image in texture mapped
3d object did not changed every frame, otherwise the speed
should be about the same.

>2. Can you alpha blend your image into the canvas?

Yes, the J3DGraphics2D is clear using
Color blackTransparent = new Color(0,0,0,0);
every frame before user call the drawing method.
Using the alpha component in the color when drawing 2d should
work fine. Java3D will automatic alpha blend the J3DGraphics2D
image with 3D background.

>3. If you have lots of overlays and gui components is framerate affected a
>lot or is it always really moving the entire 2d screen into the buffer?

Certain methods as mention in the document is optimized to only passing
the minium region affect (union of dirty region).
It will NOT always passing the entire 2D screen pixel down
for texture mapped. But if you draw two object one at upper right
corner and one at lower left corner, then the union of
the dirty rectangular region is the whole screen so you
will get worse performance.

>4. Is this completely portable?  Is there any chance that using this might
>not be compatible with console machines in the future?
>
I don't see why it is not portable if the graphics card support
texture mapping.

Note that under Solaris, glDrawPixels is used by default
to blend/composite the two images instead of texture mapping
so the speed may be different. (using we explicitly
set -Dj3d.g2ddrawpixel=false property to force using texture
mapping technique)

Thanks.

- Kelvin
-------------
Java 3D Team
Sun Microsystems Inc.

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