PDA

View Full Version : Why not use triangles?


jozizo
09-23-2009, 08:50 PM
I was going through a tutorial on modeling a head (Blender) and the author noted that I wanted to ensure that I was using parallelograms (squares, rectangles, etc.) and to not get into using triangles. Why not?

I was going along just fine, but was using my own resources and images and such. I'm extremely new to 3D modeling, so naturally I made a ton of messes (but I'm learning a lot). The thing is, with all the extruding and such, I ended up with a ton of triangles. Why is this such a bad thing?

Like I said I'm learning a lot, so I think I'm going to remodel the same head a few times, so if I need to watch for triangles I would like to make a habit of it.

Doner
09-24-2009, 10:40 PM
triangles remove edge loops from the equation. You want edge loops because they give 'flow' to your topology. This is important for deformations and also adds a high degree of cleanliness and edit-ability to your model. Triangles aren't forbidden, but try not to have them as much as you can. I hide mine in spots one can't see easily. Behind the ears, inside the nostril, behind the eyelid etc..... Look at professionally modeled heads and try to imitate their line flow. I an constantly adding and re-directing mine as I model to make sure it will all deform nicely later on. If you are simply sculpting, then the only thing you should worry about is quads - lineflow doesn't matter much. Zbrush and Mudbox like quads.

The4thAggie
09-25-2009, 01:21 AM
See attached image. Triangles cause distortions when smoothing the mesh. Even as you go up in subdivision it only worsens (see image 2)

phix314
09-25-2009, 06:41 AM
They don't distort/smooth well. This has been discussed hundreds of times... I'm sure you can find many answers that may give more in depth responses if you search.

jakeh14
09-28-2009, 06:10 PM
Interesting I should find this, as I was about to post a similar question. There are 3D artists who SWEAR by using only quads (four-sided polygons, of course). However, I just recently watched a video where the author stated (I am paraphrasing, mind you) that if you're going to spend more time worrying about everything being a quad or hiding your tris, then it's really not worth it. He was not saying ONLY use tris, of course, but instead saying that a tri here and there is okay and not to stress it.

I think there's a valid point to be made here. Generally, modelers (of organic shapes especially) wind up with poles (a vertex surrounded by more than four polygons). We hide these as best we can, and keep them away from edge loops. Is it reasonable to say the same about tris?

I'm legitimately curious what others think on the subject: at what point do you stop worrying about keeping tris (and poles for that matter) out of your model and just create your vision? It can be distracting to have to worry about everything being quads throughout, but then again if you are taught properly to begin with then maybe it's ingrained and you don't have to stress so much about it?

On somewhat a side note, he also mentions that all game engines work in tris. How true is this? I am under the assumption that Torque works in quads, but don't know this for a fact...or if other engines work in quads for that matter.

flatulentFuzz
09-28-2009, 06:24 PM
While a lot of people try and make their model entirely out of quads, it's not always necessary, or efficient.
Triangles and 5-siders can be very helpful in areas where you need some sort of "pinching", and when kept in low amounts in relatively low-deformation areas, they help add realism to organic models. The main problem with an all-quad model is for it to break past the clean, smooth, slightly unrealistic CG look, it needs to have imperfections which can only be obtained by increasing the polycount a lot, or through a sculpting app.
On the other hand, well placed tris and 5-siders give you a slightly imperfect model which adds to the realism, and you don't need to have a high poly model.

Although this is a very old example, one prominent artist I can remember using tris and 5-siders is Steven Stahlberg.

Check out the facial topology in his post. (http://forums.cgsociety.org/showthread.php?f=25&t=38469&page=1&pp=15)

himadrism
09-28-2009, 07:21 PM
does the presence of tris & NGons create problems while UV unwrapping or texturing?if they do, then how?

jakeh14
09-28-2009, 08:34 PM
While a lot of people try and make their model entirely out of quads, it's not always necessary, or efficient.
Triangles and 5-siders can be very helpful in areas where you need some sort of "pinching", and when kept in low amounts in relatively low-deformation areas, they help add realism to organic models. The main problem with an all-quad model is for it to break past the clean, smooth, slightly unrealistic CG look, it needs to have imperfections which can only be obtained by increasing the polycount a lot, or through a sculpting app.
On the other hand, well placed tris and 5-siders give you a slightly imperfect model which adds to the realism, and you don't need to have a high poly model.

This is quite interesting. Tris are common, as that's how modeling was entirely done. However, 5-siders are typically a big no-no. My personal opinion is that there are more effective methods to create imperfections (normal mapping, for example). Also, I don't know that a model with low enough poly count to need these imperfections would benefit that much from them.

Needless to say, it seems unconventional, but not necessarily in a bad way though. It would be nice to experiment with.

himadrism: My experience with UVWs would tell me no. Essentially all a UVW unwrap tool/modifier is doing is spreading out a 3d mesh onto a 2d surface. In other words, it's redistributing those polygons, no matter how many sides they have.

However, the tool/modifier might have issues dealing with anything other than tris and quads, so some manual adjustments may be in order. Again, I've never worked with 5+sided polys, so I can't comment for certain.

himadrism
09-28-2009, 10:02 PM
himadrism: My experience with UVWs would tell me no. Essentially all a UVW unwrap tool/modifier is doing is spreading out a 3d mesh onto a 2d surface. In other words, it's redistributing those polygons, no matter how many sides they have.

However, the tool/modifier might have issues dealing with anything other than tris and quads, so some manual adjustments may be in order. Again, I've never worked with 5+sided polys, so I can't comment for certain.

thanx for replying...i was basically talking about tris & 5 sided polygons in general...& not 5+ sided polygons....in hard surface modeling, when we bevel an edge(chamfer in max)...it either creates a tri or a 5 sided polygon...most of the times these are in corner areas where we need sharpness...is it ok to leave them as it is?

jakeh14
09-29-2009, 03:16 PM
thanx for replying...i was basically talking about tris & 5 sided polygons in general...& not 5+ sided polygons....in hard surface modeling, when we bevel an edge(chamfer in max)...it either creates a tri or a 5 sided polygon...most of the times these are in corner areas where we need sharpness...is it ok to leave them as it is?

Depends on what you're modeling of course, but they should be fine. UVWs shouldn't be affected by them.

jozizo
09-29-2009, 06:51 PM
Thanks a ton for all the answers. I really appreciate it.

I think I'm starting to understand the use of tris; and now I have an even greater respect for the craft. The general consensus is that I should use quads the best I can, and tuck the tris away (like behind an ear or non-camera-facing side for stills). This means that modelers are not only good enough at modeling, but have the foresight to place their edges appropriately throughout the model.

I also got an email from Glen Moyes and he pointed me to a decent video site: http://www.guerrillacg.org/. A lot of the stuff is pretty basic (which I kinda need), but there was one video that explained the need for quads visually (showing what happens when they pole up too much) and some methods of fixing them if you have a model with too many tris. Very cool. Really showed me how much learning I have ahead of me.

Again, thanks a ton for answering the newbie question.

jakeh14
09-30-2009, 09:39 PM
Another good site: http://www.poopinmymouth.com/
(Not as insidious as the title sounds)

I just learned a new technique to create noses from one of his screen caps. He's done a bunch of main stream stuff and his tutorials can be quite helpful.

In spite of my previous posts, I do my best to keep everything in the face a quad. As you'll see in Ben Mathis' wireframe shots, he doesn't have a problem with tris. It's actually better to just keep tris away from places which will morph often (mouth, eyes, noses to some degree).

CGTalk Moderation
09-30-2009, 09:39 PM
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.