Quads and Tris - a question

[OrchidFace]

I'm no pro. But I don't think i've heard anywhere that you should model in evenly spaced quads. I have heard you should model with good edge flow, and animation in mind. Higher res at deforming points and such. Good edge flow will also help allow you to tweak and build on your model more easily, and will deform better in animation process.
I think the main reason why tris are less desirable is because of how smoothing/subdividing algarithms handle them. If you have anything other than 4 edges intersecting (which is inevitable with the use of tris) new polygons will not be interpolated well in subdivision.
Then again I could be totally wrong. After all i'm no pro. But in my experience if you have 5 way intersecting edges created from triangles they will leave more of a sharp tip after subdivision. Sometimes the shader will do funky things as well if I have big N-gons, tris etc.
If its a rigid object mesh sloppiness is less of a concern.

[johnnymoha]

Agreed, Orchidface. You will need to have good clean edge loops in places where the model will deform. Ex: Places like shoulders and the crotch. You want to keep it in quads when you can, so that the smoothing will look good.

[GrogMcGee]

OK, here is my problem:
I always learned "model in evenly spaced quads!!", but then I watched the "modeling next gen characters" DVD from digitaltutors, where the instructor doesn't care about modeling in tris and quads, and saw some models of really good artists, also with a very messy mesh.
So what is right?
There are generally 3 cases:
1) I model a low-poly game character in Maya, make normal map in zbrush.
2) I model something high-poly in Maya, bring it in zbrush and make a displacement map - but this object doesn't need to deform.
3) like the case befor, but this time the mesh with the displacement map is going to deform (like a high-poly character for a cinema production).

In which of these 3 cases is it OK to model in tris and quads, what would you do?

I would suspect that in the case of the models that seemed to have polys laid out willy-nilly, in fact had good edge flow (as has been stated above). Games art tends to bend the rules on what constitutes "proper" modeling technique - what can be rendered in less than a 10th of a second has to be taken into account.

Now, as has been stated edge flow is paramount and that tends toward the creation of quads; they're easier to contol and reroute through a model. The use of n-gons are invariably required.

As a note about learning to model a character or skinned anything; it may be more benificial to aim less of quads and more good edge flow since that will likely lead to good quads.

Re. Game Art In General: the shader system in a game is what defines how evenly distributed the poly's are. That is, a per-vertex shader will look awful if you have wildly uneven distibution of vertices, while a per-pixel shader allows you to be more loose with your verts and their distribution.

When dealing with a displacement map, you'll need even distribution. However, in games one usually doesn't encounter displacment, but instead normal or parallax mapping. Which does not require (though will likely benifit from) even distribution of verts.


Objects that don't require deformation should only have as many polygons as is necessary to give the appearance required (a general rule I suppose) - in effect a static house model only needs edge flow and poly's such that is looks good in the render.

[gsokol]

Well, you do realize a quad is 2 tris right?

[NSF]

Here's a fairly long but really well explained description of how to subpatch model. It's a really great resource but it is just one person's opinion.

http://www.lightwiki.com/Fundamentals_of_Subpatch_Modeling

Although lots of other resources that I've seen of late tell you to avoid tris are much as possible. Yes we're aware that a quad is 2 tris but the way the smoothing algorithm works must be on pairs of tris. It seems as though a tri is the end of an edgeloop for the algorithm, almost like a change in smoothing is required. It seems that tris should be hidden in out of the way places or on flat surfaces, they do tend to pinch.

There's a lot of us out here in CG land who have been hidden away in bedrooms modelling, coming up with techniques to solve problems and achieving results over and over again. This doesn't mean the way we work is always the best way, maybe it's just the way we know. So these artists who use tris might have just done it that way because it's faster and easier, it doesn't mean it's the right way.

[CGTalk Moderation]

This thread has been automatically closed as it remained inactive for 12 months. If you wish to continue the discussion, please create a new thread in the appropriate forum.