Subsurfs - Tri's, Quads and Artefacts

Support Basics & Interface
1

Hi All,

I am making a car at the moment with subsurfaces. So far I have no triangles in it at all.

Trouble is, modelling like this is hard work. :-?

Question 1. Is it safe to subdivide mesh occasionally (producing triangles) or should I avoid it all costs?

Question 2. If I do have triangles and I do a test-render and see no artefacts, does this mean I got away with it - or can artefacts appear without warning later on in future renderings?

The reason for question 2 is that I am thinking of using an external renderer like Lightflow later on and I don’t want to have to redo meshes later on if I can avoid it.

Any advice on this gratefully received. :smiley:

Regards
ZoltarX

2

Triangles are safe, it’s just that quads looks better when using subsurf.

As for the artefact question, that has much to do with normals. If one of them is pointing the wrong way, the associated faces will be black, and the borders will have color artefacts.

For geometry artefacts, try to avoid overlapping faces/vertice.

Martin

3

ok… about triangles… they actually can matter when animating, since triganles tend to cause pinching when stretched and squashed. they are unpredictable since, the subsurf algorithm involves calculating the center of tension of the original face. Quads have a very predictable center, while triangles are less certain. So be careful with the tri’s, but you can use them.

Artifacts, as has been said earlier, are usually caused by normals problems, which can be solved by selecting vertices and pressing ctrl-n. with tri’s try not to have overlapping faces. with quads, it doesn’t matter as much.

4

Thanks guys.

I think a couple of triangles will make my life much easier!

It will be back to the drawing board tonite. 8)

ZoltarX

5

Triangles should be avoided at all costs
(cause unnatural creases). To find out how
lame your mesh is, try my MeshReport script:

http://www.ualberta.ca/~cwant/blender/python/meshreport.py

Chris

6

a triangle here and there is OK, but make sure that it is in an area that is already relativly smooth or you will end up the creases and bumps and your car will look like somebody took a mallet to it. Belive me, I have had it happen.

Also, when working with SubSurfs, it is best to model with as few polys as you can to get the shape right. You will be much happier with the result in the long run.

7

I second Stephen2002’s comment. I’ve had this happen on things as simple as a flowing terrain. I was getting strange rendered edges in something that should have appeared completely smooth. It turned out that that occurred only where the triangles ruled…