| Re: semi-transparent colors and z buffer [message #39916] |
Fri, 25 June 2004 13:43 |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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Patrick writes:
> I am using the map_set and plots command to create an image through
> the Z buffer. I have 2 datasets to be semi-transparently overlayed
> onto the map. But when this is done the data overlays the map, hiding
> the map data. Have searched around the web and seen several
> transparency examples, but I cannot seem to get any of them to work.
> Any suggestions?
There is only one way to get transparency in IDL, as
far as I know, and that is to use two different images
and alpha blend their values. In your case, you could
draw the map on one image and the plots on another image
and blend the two. This would be easier in object graphics,
where images have alpha channels. Or, you could do it
in direct graphics but you will have to write the alpha
blending part by hand. (See any decent computer graphics
text.)
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/
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