[gl2ps] Transparency problems

[David Thompson]

I've been using the gl2ps library for quite a while and have decided 
to try using some transparency. Whoa!, this isn't working the way I'd 
expect.

For one thing, BeginPage is checking to see if GL_BLEND is on. 
However, I turn GL_BLEND on for some primitives and not for 
others--so that check always returns false and makes it so blending 
doesn't work. I hardcoded it to 1 to get around this problem. Next 
problem arises with strange outputs of the images. I get boundary 
lines on a lot of the transparent triangles. It makes the output 
impossible to use. The Test program shows this problem also 
(especially OutBSP.pdf). I would like to try and help trouble-shoot 
this, but I'm just tracing the code and can't quite get my mind 
around how it is supposed to be working. Anybody have an overview of 
how the blending is different than the regular output?

Then I see that there is a function gl2psEnable(GL2PS_BLEND), but 
there is no example using this and the documentation really doesn't 
say what it does. Would this be the way that I should use blending 
since my primitives are turning blending on and off?

David
-- 
.............................................................................
David L. Thompson                   Visualization and Imagery Solutions, Inc.
mailto:dthompsn at vizsolutions.com    5515 Skyway Drive, Missoula, MT 59804
                                     Phone : (406)756-7472