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paulhart
12-02-2003, 10:09 PM
I have seen multiple injunctions against non-planar polygons, including the thread with "SplineGod's" comment that they are to be avoided and would get sent back with "nasty" notes if they show up in production pipelines. My question, how to avoid them... As an example, I made a simple spline guide, patched it, and as noted 19 non-planar polygons. (See example) I had been building an organic model, and had then decided to start over to avoid the dreaded "non-planars", but they appear immediately??!! I checked the manuals(first), then three book references, then Flay, found one plugin... but really think it should either be easier to fix or not create, or maybe I am missing something?? Any help/discussion is appreciated

Mylenium
12-02-2003, 10:43 PM
As long as you stay within Modeler, non-planars are ok and inevitable. You cannot avoid them due to the simple fact that (if you are really scientific about it) any polygon with more than 3 points is non-planar.

I also disagree on some of Larry's views on them in a production pipeline. My point is, as long as everything looks as intended there is no harm done. Especially when you are only working within LW (who's renderer will be able to handle such polygons under certain preconditions) there is no need to spend hours fixing "problems" that are none. Of course that does not exclude having to triple polygons in many situation, but really only if not avoidable.

If you are working in a heterogenous environment with different programs most of the time you will have to triangulate your meshes. There it is of course better to do it in a controlled way inside LW rather than relying on automatisms from import/ export modules.

Mylenium

pauland
12-03-2003, 01:13 AM
You cannot avoid them due to the simple fact that (if you are really scientific about it) any polygon with more than 3 points is non-planar.

I'm afraid that's not true.

Non-planar means that not all points share a common plane. It's perfectly possible for polygons with more than three points to be planar.

For example, if I had a ten-sided polygon whose points all had x=0, it would be perfectly planar.

Three-sided polygons are guaranteed to be planar, while polygons with more than three sides are not guaranteed to be planar, but certainly can be.

Paul

riki
12-03-2003, 03:47 AM
Check to see if they render okay. That's all that really matters at the end of the day.

paulhart
12-04-2003, 11:48 AM
Thank you for your thoughts. I was over on CGTalk and saw the following thread and thought to ask my question here. The referenced thread seemed real strong on the issue of non-planar polygons, yet I have a hard time imagining how to create any semi-organic form without them. Yes, I have rendered them fine, but the discussion seemed to say that they can somehow be avoided, or at least should be??? Thread posted below....
http://www.cgtalk.com/showthread.php?s=&threadid=104094
Thanks for the feedback all...

hrgiger
12-04-2003, 12:25 PM
as long as the polygons are facing the same way without resorting to flipping them manually, your polys are all planar. Moving the points around you can make the polys that are non-planar into planar ones. usually it doesn't matter if you are using a subpatched model but even then, I usually do most of my tweaking with subpatches turned off. It makes my mesh cleaner and it shows me that none of my polys are non-planar.

SplineGod
12-06-2003, 04:26 AM
Originally posted by paulhart
I have seen multiple injunctions against non-planar polygons, including the thread with "SplineGod's" comment that they are to be avoided and would get sent back with "nasty" notes if they show up in production pipelines. My question, how to avoid them... As an example, I made a simple spline guide, patched it, and as noted 19 non-planar polygons. (See example) I had been building an organic model, and had then decided to start over to avoid the dreaded "non-planars", but they appear immediately??!! I checked the manuals(first), then three book references, then Flay, found one plugin... but really think it should either be easier to fix or not create, or maybe I am missing something?? Any help/discussion is appreciated

Hi Paul,
Are you referring to the thread where Randy mentioned Non Planars = Bad?
Randy said that theyre bad and my view is that theyre bad only when theyre bad. I never said that a model with nonplanars would be kicked back. I dont know how a supervisor would have the time to check every single model for nonplanar polygons. Non planar doesnt always mean that they will render incorrectly. Thats up to the modeler to check out and see if there are render errors. If there are you fix em and if not you dont. In that thread I stated that if an object has a contiguous surface and the polys are all non planars but are all non planar in a nice continuous way that many times they will render fine.

If you are modeling organic things with lots of curves you do want to be careful and check for them in layout for render errors. We all know that curved surfaces will have nonplanars. What we dont know is if theyre going to create render errors. You cant determine that in modeler.

Now if youre modeling with SubDs it doesnt matter at all because the Control Surface can be totally full of nonplanars and the IMPLICIT surface underneath will be fine. SubDs are tesselated into triangles at render time in layout so they never go nonplanar.
IF you freeze your object and plan to deform it using bones or whatever you MUST triple or you will have massive rendering errors. If you reread that thread youll find, as I said, that Randy had the nonplanars = bad stance along with LWD not myself.

I hope this clears up who said what and my stance on the issue. :)