Subject:
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Re: Clipping / CCW / CW / INVERT
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Newsgroups:
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lugnet.cad.dev
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Date:
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Fri, 8 Oct 1999 17:40:02 GMT
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Viewed:
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1475 times
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Rui Martins wrote:
>
> > Actually, since LDraw doesn't do shading, transparent surfaces *can* be
> > clipped. Only edges, the top-most solid surface, and the top-most
> > transparent surface will show up in the final rendered image.
>
> Check the instructions of any LEGO MODEL and you will see an attempt
> to represent translucency/transparency, by using dots.
> If we can actually do transparency, we should to it to every polygon
> that as transparent/translucid color (maybe these are not the correct
> terms).
No, when I look at the images I see real alpha-blended surfaces :)
I've tried to turn backface culling in the transparent parts and they
looked very ugly, it's better to draw everything in those cases.
> Yes it will!
> it will allow to keep backward compatibility with every file already
> made, without changing anything. If the file is enhanced then it will
> benefit a Faster Drawing and extract functionality (real transparency).
>
> Remember that this is what is done in OpenGL, which was well though by
> Silicon Graphics, after years in the 3D business.
> To use this features, in a similar way, will simplify the making (or
> appending) of a program written in OpenGL, and probably D3D (since they
> use something similar).
Just a note to correct the statement before it gets confused:
If you keep changing states (turning backface culling on/off or
changing front faces from CW to CCW) very often, you'll get a *slower*
rendering in OpenGL (don't know about D3D). And remember that in a
couple of months nVidia's GeForce chip will be out and everybody will be
able to have hardware T&L, making rendering much faster if done in the
right way.
Leonardo
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Message has 1 Reply:
 | | Re: Clipping / CCW / CW / INVERT
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| (...) Do you know the reason why? The change-state-calls could cost a little overhead, but don't they just set some flags? And these flags would just cause negating an orientation test? /Lars (27 years ago, 9-Oct-99, to lugnet.cad.dev)
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Message is in Reply To:
| | Re: Clipping / CCW / CW / INVERT
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| (...) Thanks! (...) I knew that ! ;) (...) LDraw doesn't, but this specification is for new Programs which are backwards compatible with Ldraw, but with a bunch of new enhancements. Check the instructions of any LEGO MODEL and you will see an (...) (27 years ago, 8-Oct-99, to lugnet.cad.dev)
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