N-gons??

[dooki]

Hey all,

OK, sorry for the noob question here but: What is the importance of apps handling n-gons?


- Are n-gons poly's with more than 4 sides?
- Is it a situation that some apps cannot handle dealing with n-gons and that they convert to tri-polys or something? If so, does this conversion mess up renderings or something?


Thanks!

-Dooki

[loloallo]

Originally Posted by dooki

- Are n-gons poly's with more than 4 sides?
- Is it a situation that some apps cannot handle dealing with n-gons and that they convert to tri-polys or something? If so, does this conversion mess up renderings or something?

1- Yes (when using poy in the modelling process, with nurbs ????)
2 - I think the n-gons are converted in tri-polys (example Blender). Using n-gons provide a bad topology (but you can use them anyhow in places where n-gon is not viewed even two tri-gons are betted)

[Piem]

N'gons are not a problem for 100% flat surfaces. (but the render must accept them, anyway you can do an auto-tesselation for flat surface, the result should always work)
N'gons are evil for organic surfaces...but even for flat surfaces wich are not 100 % flat (example, with chanfers in some cases)
In example Zbrush doesn't handle Ngons but Zbrush detect them and ask you if you want to convert them.
An other example: Maxwell Render doesn't support nGons..the surfaces with more than 4 points are automaticaly ripped off..and so you may render holes !.
The best is to always think about a good modeling.

[Tartiflette]

N-gons are polygons with more than 4 vertices.
They can be VERY useful when doing architectural stuff for example or also when dealing with complex geometry before doing some clean-up.
As Loloallo said they can mess up the mesh when animating so they aren't recommended when animating.


Cheers,
Laurent aka Tartiflette

Edit : Oops, Piem's reply has completed Loloallo's answer quite well already !

[jbshorty]

Hi Dooki. When importing an n-gon to any program which doesn't support them (such as Rhino or ZBrush) you never know exactly how they program will tesselate that face. Some (such as Rhino) slash it into the minimum # of triangles required to define the shape. Some others may break it into a series of radial triangles (like a pizza). So it's better to tesselate n-gons by hand, than to leave the decision to some devilish algorithm. Also, when you have big n-gons (or sometimes when using very long polygons) you may notice some strange artifacts in the render which is caused by vertex normal averaging over long spans. Keeping your polygons of more uniform size helps to avoid this...

jonah

[shoeach]

This thread is useful for me.
CG world is still mystery world for me.

Thanks for this thread.


Syuichi

[dooki]

Thanks all!

Strange. I replied last week but it didn't post I guess. Anyway, thanks for clearing things up. I have ZB and didn't know about the import issue too.

-Dooki