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Re: Transparent texture mapped polygons [message #29878 is a reply to message #29875]

Mon, 25 March 2002 12:24

Rick Towler
Messages: 821
Registered: August 1998

Senior Member

"lyubo" <lzagorch@cs.wright.edu> wrote

> I've been trying to overlay two images and draw them in 3D. To do that I
> create two texture mapped planes (with the images as texture) but I have
> problems
> making one of the planes transparent. I create an "alpha" image, as in
> David's example,
> for the foreground plane hoping that it will be blended with the
background
> image (the other
> plane) but it doesn't work because when I add the background plane to the
> model and then
> the foreground plane (the one with the alpha channel), the foreground
plane
> will
> not show up on the screen. It is there, but is covered by the background
> plane.

Yes, objects in a view are rendered according to their order in the view
container. When texturing with an alpha channel the order of rendering
becomes important. Add items from back to front like you first tried. I
see that you are sharing the same verticies between your billboards. I am
not sure how IDL will handle rendering this since your planes occupy the
same z space but I think this is your problem. Push your background plane
back a little in z.

You can also remove the palette keyword for "alphaImage". It should be
ignored since you have passed (and will always pass) a 4 channel image but
maybe it is having an effect.

-Rick

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[Message index]

		Re: Transparent texture mapped polygons By: David Fanning on Mon, 25 March 2002 17:16
		Re: Transparent texture mapped polygons By: Rick Towler on Mon, 25 March 2002 12:24
		Re: Transparent texture mapped polygons By: lyubo on Mon, 25 March 2002 10:15
		Re: Transparent texture mapped polygons By: Rick Towler on Sun, 24 March 2002 20:59
		Re: Transparent texture mapped polygons By: Karl Schultz on Tue, 26 March 2002 08:09

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