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Re: IDLgrWindow, IDLgrVolume and alpha channel [message #33808 is a reply to message #33801]

Fri, 24 January 2003 12:08

Rick Towler
Messages: 821
Registered: August 1998

Senior Member

"Sebastian" wrote in message

> I am rendering an IDLgrVolume into a IDLgrWindow. When I get the image
> data from the Window, the image has only 3 channels. How can I get the
> alpha channel of this image? The alpha channel information surely must be
> somewhere, because volume rendering needs it.

<speculation>

I'm sure Karl can give you a technical answer but the short of it is that I
am pretty sure you can't get the alpha channel from a window by using the
Read method. I would guess that by the time the data is written to your
display buffer the alpha information is long gone. I don't know if this is
a "limitation" of OpenGL, the OS, or IDL and while I can think of a few
reasons not to do this, I can't think of a good reason to do it.

</speculation>

You may be able to get the data you need in some other way. Maybe if you
post some specifics on what you are doing someone might come up with a
creative alternative.

-Rick

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		Re: IDLgrWindow, IDLgrVolume and alpha channel By: Karl Schultz on Fri, 24 January 2003 16:06
		Re: IDLgrWindow, IDLgrVolume and alpha channel By: Rick Towler on Fri, 24 January 2003 12:08

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