Fundamental Topology Question Tris/Quads

Hi, I have a fundamental question. :o

Lets say I have a plane and want the left side skewed… so I made a skewed cut and seleted the left row:


Now I have a triangle in the upper left corner. In order to avoid triangles, I subdivide the upper left edge, and so I have just quads:


So I have a plane with a skewed left side and only quads. But I fear that this solution is too simple to avoid further trouble with Subdivision Surface Modifiers and adding edge loops. Or is this a good approach?

Thanks for help. :slight_smile:

why not skew the next vertical edge line over as well and make the top triangle a quad by subdividing the top edge of that first quad?

I think I get where your coming from, but the first thing you need to look at with your example is a fundamental question as to why this is subdivided at all. I’m going to assume that you realize that this could just be one quad. I’m also going to assume that the concern you have is with keeping this form when it has a subsurf modifier. Correct? If so the answer is to give the basic quad “edge stiffness” by using loop-cuts to add geometry where it’s needed. Here’s an example…

You most likely have a much more complex form in mind. If so i’t’s important to understand that very simplistic examples will be of little use for those trying to help. Still, imagine this was something more complex like a door of a car. The same structure would be needed to “hold” the form and provide the needed hard edges.



The above… all. Plus:

Sometimes you find you are deep in a model and changing the fundamental shape of the subdivision due to other details is not possible.

There are several ways to handle your situation depending on where you find it.

But just taking your example for instance. And assuming the edges are there for a reason and I want to patch into them with my new shape. I might follow a process such as this:



(“i” for inset)


And continuing…



creating a new edge flow from the original point of the next edge loop to create quads.

And finally deleting the edge loop:


Assuming this shape is connected on the right and on the bottom to something you did not want to change, you might also remove those edge loops. Hard to say what you situation would be. But this just one idea of many.

A triangle with quads to support subdivision.



This gives all sides two-face flows which subdivide accordingly. Could also easily add support loops to keep the shape.

The triangle was subdivided, middle triangle subdivided again, and collapsed edges on the middle triangle from that.

Good question :wink:

But actually I want to use this technique in a larger scale and reduce the number of edgeloops with it

Thanks for all the other suggestions… I need to read this more often to understand.

Actually I retopo’d an avatar mesh with quads only, and now am trying to cut garments from it. But I while doing the cuts eith the kife tool, I try to retain the quad structure because after the cuts, the garments might be subdivided.

So actually I want to do something like this:


but of course I hate the triangles and n-gones on the left edge

Well just use the knife tool, sometimes it is good to work a bit further than the edge. then you should been able to delete the edges, vertices who create the triangle

Same thing than Richard, but i start direcltly the knife. You could do this knife cut as further inside it is needed, then even remove it and add new loop then.



In this case i have just create a new loop ( still highlighted ), then remove the initial loop who was create the problem .

another faster way would be to faces to tri’s
then apply a subsurf level 1 and done
you got all quads all over !

another way use a Nurbs surface shape it then convert to mesh!

happy bl

I do this all the time. I don’t mind just making a mess to get the cut I want. Then - as others have shown many examples - it is just a matter of going back and editing things to work as quads again.