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Bob27
06-18-2004, 03:30 PM
I have read in some poly subdivision tutorials that it is a kind of necessary to avoid non-quad polygons if you want a good
topology, I have also read that tri-edge faces might cause problems in animation. Is that right? I was trying to abide by this rule and spending time edge-looping and making quad faces.

But I have noticed that some other standard tutorials on poly modeling do not abide by this rule. Like the one in low-poly game character making (Tobby) in the 3dsMax Tutorials. There you can find 5 sided, 6 or even 7 sided polys and even few tri-polys.... So what's the rule? I am asking this from pro-guys working in game or movie industries, Should I strict myself to quads or it is not that much important for the end result in animation?

Jb5k1
06-18-2004, 07:13 PM
yea, this was a curiosity of mine too

it seems alot of times games use alot of odd numbered polies, but i have no idea why

i always try to use quads but im not sure y, and sometimes for games i've been told to triangulate it


wouldn't this just create excess polies?

turumdarak
06-18-2004, 07:46 PM
From what I understand, you should have any face with more than four sides when doing SDS,HyperNURBs,etc. and preferably no tris.
Tris will create a pinch, which can occasionally be useful, but should be avoided for the most part.
Anything higher than a quad will NOT look good smoothed.

For games, the end count MUST be tris, that's all that they will take. When working on a game model, an n-gon can be used because it will become a set of tris in the end.

For just poly modeling, tris, and quads are best, others can be unpredictable.

I haven't ever done any animating, but I think that occasionally the tris would cut into the face that was bending causing an unwanted depression.

From what I understand.

Hope this helps.

Bob27
06-18-2004, 08:06 PM
Thanks for your reply turumdarak and Jb5k1,
yet I wish some pro guys involved in animation and game would bother answering this question too, so we all benefit.

Tahl'eN
06-20-2004, 11:05 AM
turumdarak's got it right. Video game models will always end up as tris, and quads act kinda funny when skinned and animated at that low resolution.
However, if you're building a low-res cage to smooth (whatever the method) you want to keep quads becasue everything else (tris included) doesn't smooth out as nicely. (read: pinch points).
The other reason to keep everything in quads where possible is that it's just plain nicer to look at a nice consistent set of quads than it is to look at a mass of triangles or to wonder if that thing that looks like a quad is actually a pent or something else.

Bob27
06-21-2004, 08:50 AM
So let me summarize what I understand from what Tahl'en and turmdarak have said, and please correct me if I am wrong:

1- For games It is necessary that the end product should be all tris otherwise unpredictable pinching might result in animation.

2- More than 4 faces for each polygon might cause problems when we triangulate our mesh. (?) So while modeling we should avoid more than quads.

3- We should not have tris also while modeling, although at the end we are going to triangulate the whole mesh. But here I am confused , if it is necessary for games to triangulate at the end why shouldn't we use tri faces while modeling?

4- In general, it is good to model our character or scene(?) using all quads but at the end we should convert to tris using for example the tesselate modifier in Max. Here another question arises in my mind, while doing the official Tubby character modeling Tutorial in Max, they never mentioned that it is good to use quads and in practice there are lots of 5 or 6 or even some 3 sided polies. And as I always assume that the applications tutorials are Standard in all ways, I am confused again.

Tahl'eN
06-21-2004, 09:25 AM
Hmm.. Just checked out that Tubby tutorial. It's not really all that great for actual low-poly modeling. It's modeling a low-poly cage for meshsmooth, which is a different idea alltogether. So, the first thing you have to consider is which route you're traveling down. From the sound of things you're going for game modeling, so I'll target my answers that direction.

1-Not pinching so much as popping as the auto-triangulation (because video cards only render triangles, ultimately) attempts to keep all faces convex.

2-This is the same idea as as 1, essentially. Triangulation of faces that have more than 4 points are ever more unpredictable when it comes to popping durring animation and even more likey to have the texture on that face stretch and warp.

3-Avoiding tris while modeling applies to meshsmooting more than low-poly results as it'll all be triangles eventually anyway. The "only quads" rule is generally a lot of snobbery, but ending up with your final model in quads makes it a lot easier to read, and is more likely to impress other people when you show it off. (always fun)

What it comes down to is, don't worry about what shape your faces actually are while you're modeling. It's the end result, not the process that's ultimately important. So build however you want, and then clean it up to make it quads (and probably a few tris) for your final show-off peice.

turumdarak
06-21-2004, 06:16 PM
Bob27,

I was just giving general guidelines.
N-gons CAN be used when modeling, just be sure to remove them before doing your final render, that's when it will be unpredictable.

In smoothing, quads give consistant mesh flow which helps when animating.
When I mentioned tris and animating, I was still thinking about with smoothing, with game models it should probably be tris when you animate.

Nicool
06-21-2004, 07:29 PM
odd numbered polies on game models

No matter, anyway all plaoies will be turned to tris on baking. Triangulate it while modeling only if you want to manage the way it will be triangulated on some areas.

Bob27
06-21-2004, 07:56 PM
Thanks all, excellent comments, now I summarize it briefly:

1- Model your character freely and don't care much about quads

2- Once the modeling is done , then change all greater or fewer than quads to quads, but you can leave a few tris.

3- At the end smooth it, that is tesselate it to tris for games.

Right? I think this is the summary of what has been said.

Now please look at the following image, at left you have Tubby before tesselation and at right after alll faces are transformed to tris , 7000 faces.
Is that what we should do for games? Isn't 7000 faces too much? what else could we do?

http://img35.imageshack.us/img35/2150/Tubby-tess.jpg

Tahl'eN
06-21-2004, 11:11 PM
Woah. Ok, just realized that it's been a while since I've used Max. In Maya, there is a function called Triangulate. In Max, all you have to do is select all the edges in the model and make them visable, as Max essentially works in all tris anyway. And if you are planning on smoothing instead of just working low poly, make sure that you set the meshsmooth to operate on quads rather than tris.

uncon
06-21-2004, 11:29 PM
If you are subdividing, using meshsmooth, metanurbs, etc... anyone of those types of things quads can be a little more predictable. The computer likes the quads because it is easy to devide them up.

Otherwise I just try to model as cleanly as possible and quads help me see the lines on the model.

Nicool
06-22-2004, 07:23 PM
Bob27 : The difference is made between triangles count (3000 max for Game Art Comp #8 for instance) and polygons count (polygons that could be made of three, four, five, and more edges).

For a game model, work with 3,4,5-sided polygons. As I said, transform a 4,5-sided face to triangles if you want to manage the way the edges will be oriented. Otherwise, do not worry about it. But do not work with tris on whole mesh, it will make harder to work on (modifications, cuts, UVs, ...)

A bit more info. Working in quads only is needed in some high-res modeling cases, but that is a master issue.

Bob27
06-23-2004, 01:57 PM
Thanks all,

Thalen, as I understand from your last reply: "In Max, all you have to do is select all the edges in the model and make them visable, as Max essentially works in all tris anyway." So I did not need to tesselate as I did in the Tubby image above. I make a low poly characater using mostly quads in Max and then just convert it to "Editable Mesh".

One difference between Max and Maya is that in Max we have both TriMesh and EPoly, but in Maya we just have Epoly. The structure of TriMesh is based on vertex-face but Epoly is based on edge-face. So, while 2 adjacent polygons in Poly share the same edge in TriMesh they don't, each having its own edge.Now in Max as you said we don't have to triangulate. In the image below , the left Tubby is a Poly one while the right has just been converted to Mesh and the hidden edges made visible.

http://img38.imageshack.us/img38/4900/Tub-Max.jpg

That is the equivalent to the Triangulate function in Maya:

http://img31.imageshack.us/img31/1448/Tub-Maya.jpg

So, basically, for game modeling we should model a low poly character made of mostly quads ( few tris or 5 sided are allowed) then convert it to Mesh in Max , or Triangulate it in Maya.And that's the synopsis I guess.

Nicool, I visited your contest lowpoly soldier, its great, i will try to learn from it and apply in my future low-poly modeling. Excellent,bon travail,j'ai vecu a Lion et a Chambon sur Lignon en France, des annes passees!

Tahl'eN
06-23-2004, 05:57 PM
Sounds like you've got it. And remember that the term "polycount" actually referrs to the triangle count, so all 3 (4?) different tubbys in your last example have the same polycount in the final examination.

Nicool
06-24-2004, 02:12 PM
In Maya, to get the triangle count (which is not displayed in view header) you just have to type polyEvaluate -t (after having selected any object(s)) in the command line :thumbsup:

Buhrmi
06-26-2004, 07:58 PM
Once I've saw a mini-tutorial showing some situations with ngons wich can be easily "remodeled" to quads. does somebody have the link?

Another thing that bothers me: when using ngons and quads i'm allways afraid that they get unplanar. That is, when working with quads, if you move a single point in your mesh quads will become unplanar. I thought that that is a bad thing because tesselation becomes unpredictable?

Tahl'eN
06-26-2004, 09:15 PM
With quads, planarity only matters if your points are REALLY off-axis and you can see the extra triangle edge showing up when you rotate around it. N-gons are touchier, which is why I turn them into sets of quads and tris really quickly.

hpslashluvr
06-26-2004, 09:44 PM
if you check out the topology tutorials in this forum and in the maya forum (sticky) there are plenty of very pro modelers and animators out there that use tris and n-gons. For example, if you take a look at Stahlberg's new generation mesh it is practically non-quad in many places, and it deforms perfectly well. However, I'd probably guess you are not at the point where you can start making n-gons whereever you'd like, so I'd probably stick to edgeloops and quads (tris for games I think). Apparently Stahlberg's method works fine for him in Maya, I might test it out in Max.

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