Four sided poly faces
 

Just got through the cartoon dog tutorial. First, I'd like to say it's a great tutorial, and I learned a lot.

My question... why is it important to try to keep the polygon faces to 4 sides? What's wrong with five side or three sided faces?

Depending on what you do with 3d modeling, it's best to keep your geometry in quads (4-sided polys) for the sake of deformations. Most game platforms have no issues with triangles. 5+ sides are going to give you outright bizarre deformations when animated.

If it's going to be a perfectly flat surface that is not going to be animated or interacted with (dynamics), you can have 100+ sides for all anyone cares. :p

I think I now understand what you mean, thanks! How come 3 sided won't matter in games? Won't your objects be moving around, too, like it would in an animation?

At render time all the faces get converted to tri's anyhow for rendering, if your model has all quads then the conversion is very predictable as it's a case of splitting the quads in half but if you have n-gons (5sided or more) then you have no way of knowing how the n-gons will be split to convet to tris and can give unpredictable results which is another reason to stick to quads even for a still shot.

thanks;) ;) ;) ;) ;) ;)

And to continue where JS left off.

All games render in real time so all models should be triangulated prior to importing into an engine. Triangulation works 100% when models are all quads.

The issue is all about rendering, also its worth noting if you are going to convert your polys into Sub-D or NURBS then n-sided polys will give a lot of issues as will 3 sided. So keep 3 sided to a minimum (only use where there is no other option) and never have n-sided polys.