Subject:
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Re: Once again, a relativley major bug...
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Newsgroups:
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lugnet.cad.mlcad
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Date:
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Wed, 17 Sep 2003 17:00:11 GMT
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Viewed:
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4315 times
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In lugnet.cad.mlcad, Andrew Keyser wrote:
> Excuse my Direct3D statment, I guess OpenGL is the way to go because of
> the linux crowd (plus, thinking a little more....OpenGL is actually
> faster than Direct3D).
> But the rendering engine in my view is less important mainly because as
> I said in my first post, it will create more culling problems than it
> might be worth. I've experienced this firsthand when importing a brick
> into Zmodeler: primitives that have been "flipped" are inside-out. I
> suppose anything that reads BFC statments should correct this but
> unfortunatley the LightWave convertor I used before convering them to
> 3DS doesn't.
> Andrew
I can certainly appreciate why you suggested Direct3D, and I personally didn't
interpret it to mean that you would be disappointed by an OpenGL renderer. I
believe that the performance differences between OpenGL and Direct3D are fairly
heavily dependent on the video card. Cards made by nVidia tend to run faster in
OpenGL, but other manufacturers' performance characteristics vary, I think.
Also, while it may or may not be possible in Direct3D, OpenGL supports something
called two-sided lighting, which basically makes it so every polygon gets lit on
both sides, instead of just one side as normally happens. It also allows the
developer to choose whether both sides of a polygon get drawn or just one. Put
the two together, and everything works fine.
Alternatively, if you don't care about specular highlights (shinyness), you can
just use two directional lights that point in opposite directions. Then, as
long as both sides of every polygon are drawn, they will show up fine. LDView
supports both mechanisms (based on a preference setting).
Having said that, I can also say that writing an OpenGL renderer for LDraw
models that runs with reasonable performance isn't exactly trivial. It's not
all that difficult to get basic functionality, but neither is it trivial. As a
point of reference, I had the original LDView far enough along to release a test
release after about a month of work, but I already had a basic OpenGL rendering
engine to use as a starting point that I wrote in college.
--Travis Cobbs
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Message is in Reply To:
 | | Re: Once again, a relativley major bug...
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| Excuse my Direct3D statment, I guess OpenGL is the way to go because of the linux crowd (plus, thinking a little more....OpenGL is actually faster than Direct3D). But the rendering engine in my view is less important mainly because as I said in my (...) (21 years ago, 16-Sep-03, to lugnet.cad.mlcad)
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