Tris are things you would avoid when it comes to shading, and good Topology, so do Tris do any good?
Also I am currently working on Game Asset Creation and I would like to know if Tris are actually something I want definately to avoid.

enter image description here

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    Not sure this is a duplicate? The other question is relating to character animation. – ideasman42 Aug 23 '15 at 23:38
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    Not a duplicate IMO, highly related yes, but that question is asking about the problems with tris. Not the potential advantages. – gandalf3 Aug 23 '15 at 23:41
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    I find this to be a good read on this and other topics: blog.digitaltutors.com/modeling-with-quads-or-triangles – cegaton Aug 24 '15 at 3:09
  • i'm not sure either anymore, but it seems that the answers and links on the proposed duplicate cover most (if not all) that can be said ( even outside of the character animation scope) – zeffii Aug 24 '15 at 7:32
up vote 15 down vote accepted
+50

There's a big misunderstanding regarding tris. A lot of people say that you should never use tris, and they're somewhat right. But the main reason behind not using tris, is because they can be harder to work with, and they can cause issues with deformations. Although, before exporting/baking your model for use in games, it's advisable that it's triangulated anyway.

The thing is, people tend to go to overly extreme lengths to avoid tris, when in reality, adding a tri is a lot better than trying to work around having one.

One other thing to keep in mind, is that all faces are converted to triangles at rendertime anyway. You aren't speeding up rendertimes (If I'm not mistaken, some of the optimizations that are being added to blenders viewport are actually for quads only) but by using tris, but you are controlling how the faces are cut up (this is the big thing that effects shading).

Tris also cut off edge loops. So if you do something like this

enter image description here

and then you try to select one of the edges,

enter image description here

it will stop at the triangle. The same thing happens for both Tris, Poles, and N-Gons.

So, advantages to using tris

  1. Can keep topology simpler in certain situations.
  2. Much more effective at controlling shading on low poly models
  3. Stops edge loops
  4. Controls how the surface will be cut up, instead of allowing it to be randomly done at render time.

Disadvantages of tris

  1. Can be harder to work with at times
  2. Can cause issues with deformations and subserf
  3. Stops edge loops

In games however, There is a stage in the process where triangulation is often unavoidable and should be carefully embraced.

There is a point in the video game workflow where your game model should be completely triangulated, because most game engines will robotically do this for you if you don't, with often undesired results. Some concave surfaces will become convex and vise versa, while some unwanted/useless loops form from the resulting triangulation. You'll want to triangulate it before you export, and DEFINITELY before you bake normals. Here are two big things that can go wrong if you don't.

surface/color baking, especially normal baking, where you transfer details from Hi-res objects onto low res objects are very dependent on how a model has been triangulated. Rays cast from the high res surface to the low, virtually filling in low res gaps with information. So that if you export a model and it's map out to a different program, the triangles may be automatically cut differently to how they were in the other program, resulting in unwanted artifacts.

Surprising deformations/shape, The way that you animated/modeled the object may appear different because of the engine's method of triangulation, 'what you see is what you get' should be the aim. (this may need a better explanation.)

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    the bit in your answer, about Tris giving the user control of how a surface is cut up, in my opinion, is a major advantage, and belongs in your summary of advantages. – brasshat Aug 24 '15 at 2:58
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    They are also not handled well by subsurf (though they're not as bad as n-gons). – PGmath Aug 24 '15 at 3:04
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    Agreed. And as for an advantage to tris, I have found cases while modeling rocky terrain where quads made the terrain look too grid-like and fake, but tris on the other hand made for more natural-looking mountains, etc. Since terrain isn't something you'd deform (except in maybe large-scale disaster special effects) there was no reason not to use tris. The geometry subsurfed and displaced in a less uniform, less predictable way, and looked much better. – Mentalist Aug 24 '15 at 6:11

Tris can also be a benefit to make sure all faces are the exact same. For example, today while sculpting, I started from a cube, blender automatically triangulated the faces when I clicked "dynamic topology", and, unfortunately for me, it didn't triangulate them symmetrically. When I was dome with my sculpt, looking over to make sure everything was symmetrical, look at the error that one little misplaced tri turned into! the entire side of the head is different (it still looks cool)

enter image description here enter image description here

Now, I plan to re-topo this before using in a game, so it won't cause me much trouble, but you can see the potential error that could have been avoided by manually dividing the faces into tris before I sculpted, rather than leaving it to the helpful, but clueless blender.

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