Subject:
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Re: LDForge - dev. plans and call for help
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Newsgroups:
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lugnet.cad.dev
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Date:
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Wed, 31 Mar 2010 22:59:53 GMT
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Viewed:
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30223 times
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In lugnet.cad, Santeri Piippo wrote:
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In lugnet.cad, Travis Cobbs wrote:
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The only polygons that LDView sorts are transparent ones. Everything else
is handled by the OpenGL depth buffer (glEnable(GL_DEPTH_TEST), followed
by glDepthFunc(GL_LEQUAL)). Transparent polygons need to be sorted before
being drawn, and LDView does what you describe above for those. (There’s
more to it than that for transparent polygons; sorting is just one step.)
Sorting by the distance to the centroid is only an approximation, but it’s
good enough to look pretty good for transparent polygons. It’s not good
enough to be used as the primary means of hiding geometry that’s farther
away from the viewer.
--Travis
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I see.. but problem is that if I use glEnable(GL_DEPTH_TEST) then my
polygons won’t render at all. Tutorials related to OpenGL explicitly told not
to use GL_DEPTH_TEST because of this.. how did you avoid it?
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In order for GL_DEPTH_TEST to work, you have to clear the depth buffer at the
same time you clear the rest of the screen:
glClearDepth(1.0);
glClearColor(0.0, 0.0, 0.0, 0.0);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
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(Note: the glClearDepth() and glClearColor() calls above aren’t really
necessary, since they pass the OpenGL default values, but just in case you used
some other value, the above is what you want for glClearDepth().)
--Travis
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Message has 1 Reply:
Message is in Reply To:
 | | Re: LDForge - dev. plans and call for help
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| (...) I see.. but problem is that if I use glEnable(GL_DEPTH_TEST) then my polygons won't render at all. Tutorials related to OpenGL explicitly told not to use GL_DEPTH_TEST because of this.. how did you avoid it? (15 years ago, 31-Mar-10, to lugnet.cad, FTX)
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