Subject:
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Re: Several replies to CLIPPING / WINDING
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Newsgroups:
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lugnet.cad.dev
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Date:
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Tue, 19 Oct 1999 12:51:18 GMT
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Viewed:
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344 times
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Rui Martins wrote in message ...
> R> > If a certified part-file can turn clipping on, then any certified
> R> >file can use clipping. Where's the difference between a certified
> R> >part, and any other certified file?
> R>
> R> Parts are objects with obvious orientation. You are not in doubt what
> R> is inside/outside of a part!
> R> However, consider the 4-4cyli.dat. Even if its orientation was defined
> R> and it was certified, you could not use that info for clipping
>
> Not quite! Remember the special cases I refered!
> You could, because if you assume that this is a building block used to
> make parts, which are solid (i.e. closed) than this can be clipped.
>
> R> if it was not referenced from a certified part, i.e. a part that have
> R> gone through considerations whether to use INVERT or not.
>
> Optimizations are local to each specific file (.DAT).
>
> R> Because the orientation of parts is natural and intuitive, certified
> R> parts would be the right place for enabling clipping.
>
> Also, NOT only, primitives also.
> every .DAT file which has tris or quads is a candidate for CLIPPING.
>
> R> And it would be safe and legal to do so, because rendering programs
> R> keep track of transformation-inversions.
> R>
> R> You can of course enable clipping in your model, but it wouldn't
> R> have any effect unless you have tris or quads in your model.
>
> Touche'.
I am trying to find out when to actually start clipping.
You say "every .DAT file which has tris or quads is a candidate for CLIPPING",
but when can a program use that info?
Would you require an unbroken chain of certified DAT files?
> R> I agree with Gary Williams that the CLIPPING is somewhat redundant.
> R> CLIPPING ON/OFF could be accomplished by WINDING CW/UNKNOWN.
> R> The CLIPPING is "syntax sugar", not a functional requirement.
>
> That hurts! :( :| :) I'm ok now
>
> No that is not the case, because as I have already said, an optimized
> .dat file will have only the meta command "0 CLIPPING ON" [1]
> The fact that winding is correct does not necessarily allow you to due
> clipping. It's required by clipping, but WINDING (CCW/CW) does not
> imply clipping.
No, but what is the sense in making winding correct and turn off clipping?
/Lars
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Message has 1 Reply:
 | | Re: Several replies to CLIPPING / WINDING
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| (...) By candidate, I meant, someone could optiomize it, a place a 0 CLIPPING ON meta-command on it, and get some benefit. If you use enable clipping, but you have no graphic primitives in your file (assuming clipping is stryctly local), than you (...) (25 years ago, 20-Oct-99, to lugnet.cad.dev)
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Message is in Reply To:
| | Several replies to CLIPPING / WINDING
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| R> If you keep changing states (turning backface culling on/off or R> changing front faces from CW to CCW) very often, you'll get a *slower* R> rendering in OpenGL (don't know about D3D). And remember that in a R> couple of months nVidia's GeForce (...) (25 years ago, 18-Oct-99, to lugnet.cad.dev)
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