View Full Version : Polygon flow and 3 vertices polygons.

hub73

10-02-2008, 02:46 AM

Hi !

Today i'm trying to model some characters cartoons (subpatch). I notice that it is a bad thing to have 3 vertices polygons inside my model.

Always when i've them, it is difficult to convert them later to quads. It is also more complicated to use tools as bandsawpro or cut. Difficult also to modify the polys flow with spin quad... Finaly i notice that modelers gurus try not use 3 vertices polygons inside their character.

I'm newbie, sometimes it is more easy for me to weld some points to correct a bad polyflow ! And produce nasty 3 vertices polys. But today i'm trying to evit this and keep only quad inside my models. Is it a good technique ?

Thanks to share your experience with this !

meshpig

10-02-2008, 04:59 AM

Hub

Yes, as a general rule you aim to model in quads but that's not to say triangles are nasty. For example a triangle is better than a single point in some instances and in others unavoidable. I mean a five point poly is just a quad and a triangle combined??

m

SplineGod

10-02-2008, 05:33 AM

You can have triangles and sometimes theyre even beneficial for some structures. What you want to avoid is multiple triangles sharing the same vertex (poles).

Kuzey

10-02-2008, 06:36 AM

Jonny Gorden, of "cartoon character creation book" fame, doesn't seem to mind having a few of them in his characters :D

Kuzey

Surrealist.

10-02-2008, 06:41 AM

Hi !

Today i'm trying to model some characters cartoons (subpatch). I notice that it is a bad thing to have 3 vertices polygons inside my model.

Always when i've them, it is difficult to convert them later to quads. It is also more complicated to use tools as bandsawpro or cut. Difficult also to modify the polys flow with spin quad... Finaly i notice that modelers gurus try not use 3 vertices polygons inside their character.

I'm newbie, sometimes it is more easy for me to weld some points to correct a bad polyflow ! And produce nasty 3 vertices polys. But today i'm trying to evit this and keep only quad inside my models. Is it a good technique ?

Thanks to share your experience with this !

The way I approach it is this:

It is like a puzzle I am trying to solve. Like one of those number games where you have 9 numbers and they have to all fit in a row and not repeat. You keep working it and through the process of elimination you figure out how to make it work.

OK so this has nothing directly to do with modeling sub patches, but it is the same mental approach. You are looking at a problem that you have to solve and you keep at it until it becomes easy to see how things will work.

But in modeling I have come up with a simple mathematical formula that is always in the back of my mind and it helps me jump to the next move much easier.

It is very simple:

If you have a mesh that is all quads and one triangle there are two simple solutions you can use to turn that tri into a quad:

1) Add an edge loop.

2) Remove an edgeloop.

And...

If you have a mesh with all quads and one 5 point ngon the formula is the same.

The main thing I concentrate on is getting a good polyflow with quads first. Make sure I have those where I want them. If I get a triangle that is not solvable easily, I will leave it till later and finish the mesh. I will then look for any ways to solve the triangles that remain I was unable to get rid of. I might find then that there is an easy solution. If not I will try and simplify my mesh even more.

But here is a clear simple example of the formula:

1) A tri with quads

2) Solution 1

3)Solution 2

4) An ngon and quads

5) Solution 1

6) Solution 2

Surrealist.

10-02-2008, 06:41 AM

And number 6.

hrgiger

10-02-2008, 07:43 AM

I lost the 'must have all quads' mentality a long time ago when I realized how little it mattered. You have to know where to use them. sometimes a trinagle can alter the shape or curvature of a mesh when subdivided. I don't really think about it most of the time, but generally I use them to either step down geometry from dense to sparse or I put them in places where it's not going to be seen anyway (in the nostril, top of the head, inside a fold, etc...) just to avoid any problems they may or may not cause. I do try to use quads as much as possible but I don't add unnecessary geometry, just to turn a triangle into a quad (such as bandsawing a strip of quads that dead ends into a tri just so it becomes a quad-that's silly unless of course that particular tri is causing a problem).

Surrealist.

10-02-2008, 08:40 AM

Yes indeed. But it is generally a good idea to learn the rules before you break them. I don't see triangles as a part of any rule. I see it the other way. Quads make great polyflow. Triangles just show that that flow has not been reached yet. Now once you get to a point as a modeler you are willing to live with a few, that's fine. But you have to get there first. First it is a good idea to learn to avoid triangles not because they are bad but because they show you places where you could have done it better with quads. Also removing triangles is just as much of an opportunity to reduce the mesh as they are to increase the mesh.

More on the triangle math:

You can think of it also this way. Let's say you did add an edge. Well it has to go someplace. Let us say that the triangle was in a part of the mesh that was a lean as you could get it because of detail. So you chose an option that would make it a quad but also actually improves the flow.

Basically - over simplified of course - you did this:

http://www.newtek.com/forums/attachment.php?attachmentid=64113&d=1222951232

Then you bring it out to a point in the model where you want to then step it down. Say from a highly curved part to a flat part. So you reverse the math now to step it down by attaching it to a corner to make a triangle like so:

http://www.newtek.com/forums/attachment.php?attachmentid=64112&d=1222951211

Now you can step down the mesh. But because you added a tri you now can reduce the mesh and get rid of one edge and two loops like so:

http://www.newtek.com/forums/attachment.php?attachmentid=64114&d=1222951241

Surrealist.

10-02-2008, 08:47 AM

Three images that explain a little better.

hub73

10-02-2008, 09:26 AM

Jonny Gorden, of "cartoon character creation book" fame, doesn't seem to mind having a few of them in his characters

http://www.zigwigwis.com/lw/lea_v1.gif

It is true, look my model legs ;-)

It is very time consumming to produce a rigged character for a newbie !!! I mix several technics from books, videos !!! Today i'm here. I continue to work on this model !

hub73

10-02-2008, 09:53 AM

http://www.zigwigwis.com/lw/lea_v1b.gif

rrrr triangle !!!!

Surrealist.

10-02-2008, 12:14 PM

LOL!

Two quick samples. Plus one and minus one. Probably would have to have the model to actually come up with the flow but these are just examples of the concept.

Kuzey

10-02-2008, 12:27 PM

Have a look at this tutorial, it's for Max but it should give you some ideas.

http://www.3dtotal.com/ffa/tutorials/max/joanofarc/joanmenu.asp

Good luck,

Kuzey

JeffrySG

10-02-2008, 01:08 PM

^that's a great tutorial series, Kuzey! cheers!

This is probably not as relevant as Richard's great solutions above but I came up with this step down guide for adding or removing geometry but keeping quads. It might help in some situations. It's on my website's reference page if you need to find it again.

http://www.pixelandpoly.com/graphics/referenceimages/step-down-guide.png

Kuzey

10-02-2008, 01:26 PM

Actually, I was thinking he might want to start the model again. You know, it gets easier the second time around and following a tutorial won't hurt either.

But it's all good in the end :D

Kuzey

Surrealist.

10-02-2008, 01:34 PM

Jeffry! Very very very cool! Yet another way to break the "mystery of it all" and put it into simple practical terms. Something to really look at and learn from. I don't think I have ever sat down and sketched out all the mathematical ways to step down like that. Inspiring. :)

JeffrySG

10-02-2008, 03:47 PM

Thanks, Richard.

I'm sure there are a ton of other 'step-down' techniques. I would think that for organic modeling many times they would not follow a straight 'line' the way that these do here. And they might be more three or four sided, if that makes sense. If I ever see or think of a new way I'll just jot it down on some paper and try to remember to add it to the chart. Feel free to add to our growing list!

For me it's easier to see it as a single example, and then try to fit that into a model if needed.

Surrealist.

10-02-2008, 10:49 PM

Yeah I agree. Because a mesh can be so daunting at times it is much better to look at it simply. Especially when beginning. I love it when I come up with something that is simple. Like the add one minus one formula above. So now when I see a triangle or an ngon I don't have to think anymore about it. I know I have to add one or subtract one. And if I see two triangles and they are relatively close I know they can cancel each other out and I won't have to add anything. All I do then is redirect the flow and then eventually merge them or if I am adding an edge to one I'll route it to the other in some way.

hub73

10-03-2008, 06:49 AM

Two quick samples. Plus one and minus one. Probably would have to have the model to actually come up with the flow but these are just examples of the concept.

i'm tring to do example 1 but without success ! Could you detail more ? (tools to be used). Here my initial model if somebody understand better than me Surrealist method ;-)

Download :

Initial model here (http://www.zigwigwis.com/lw/lea_tris.lwo)

Thanks !

Surrealist.

10-03-2008, 07:04 AM

The first thing I do is turn off subpatches then I select the polygons in the area that I want to change and I use the merge polys command to merge polys where I want to draw a new flow. No certain technique here. Just logic based on what it is I want to change. Then I delete any points that my still be stranded or attached to a polygon edge. Then simply go in and use the add edges tool to draw my new flow onto the model connecting the to points or to an edge. During this process I will toggle CC subpatches to check as I go until I have all quads. And as I draw new edges I may use the merge polys command also as I go.

This technique is covered in more detail in my tutorial.

EDIT: if I get a chance later I'll take a look at the model.

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