Subdivision Triangle Issues

So I’m working on a polygon mesh that I’m subdividing into an ungodly high polygon count mesh. It’s not all that unusual, but it’s my first time working in this way in Blender. Unfortunately I’m struggling a bit with Blender’s subsurf modifier. Apparently it just hates triangles! Any time there is a triangle instead of a quad in the mesh, it gives this weird circular topological pattern that looks really bad. So I’ve burned a lot of time with this mesh avoiding triangles at all costs, even when it made sense to use them. But I’ve finally run into an instance where I have to use some triangles - joining two meshes together. There just has to be a couple of tris in it, no matter how hard I optimize. And it looks bad! The first image is what I’m doing, and the second is an exaggeration of changing everything to tris to show how bad it gets.

Is there any solution to this? Is there a way to subdivided while having a couple of tris and not have it not make a mess of the topology?

1 Like
  1. See if remesh modyfied gives you desired results if not try point 2.

  2. You can use shrinkwrap modyfier and extrude edge or vertex of other object and retopo your hihgpoly mesh. If your mesh is symetric you can cmbine shrinkwrap with mirror modyfier

Could you show us your mesh with Subdiv disabled? When subdiv modelling, you should avoid tris and ngons

That’s not really the point? I mean, I’m asking if there is a way to subdivide with triangles without the barycentrics going nuts…

EDIT: Well, here it is anyway I guess. It’s WIP of course so it’s a little messy still! But I certainly don’t know of a way to not use these two tris with these geometry, hence me hoping for some way to subdivide this nicely in blender.

gross-subsurf3

I asked to see the base mesh, because without seeing it, it’s hard to tell exactly what’s going on. But my point remains - Subdiv doesn’t like triangles, you’ve pretty much hit on that yourself anyway. Another issue I see is that you have 2 separate levels of mesh density. I don’t know what it is you’re modelling, but general rule of thumb when subdiv modelling; keep the mesh as low poly as you can. Let the subdiv do most of the work. I see a lot of close together edges that could be removed. My suggestion would be to clean up the mesh some more, as you mention you’ve already done, and delete some of the edges you don’t need. Try and keep faces as square as possible.

Very rough example of what I mean

bamesh

1 Like

Yea I know, that’s kind of why I was avoiding showing it, there’s still a lot of work to do to get these together properly.

But um, yea, I guess I’m just going to have to keep spending effort working around tris for this mesh. sigh I was hoping there was some sort of tool or something that was able to subdivided like this but was more tri-friendly for situations like this…

Have you tried blenders Remove Tris? I think it’s like ALT J in edit mode or something. (Look it up to be certain). It’s not great, but might be able to remove a few.

It’s more the fact that subdiv with tris is less predictable. You can use it, but as you’ve show, it has varying results. One solution would actually be to retopologise the mesh. It’s pretty easy to do, but the basic idea is you use a new mesh, and shrink wrap it to the old one. You then extrude edges etc…like you normally would, but it will stay stuck to your old mesh, so you don’t really have to worry about modelling, it’s more about vertex placement and topology…There are some vids on YT on how to set it up; it’s pretty straight forward. It might be quicker than removing edges, and re-working what you have to remove the tris.

I’m sorry I didn’t see this earlier. The triangles can be removed in a reasonably straight forward way. The first image below shows a mesh patch matching yours, including the triangles. The second shows the “bad” part removed, creating a hole in the mesh. The top and bottom of the hole (highlighted in blue) both consist of five edges. However, the left and right (highlighted in green) don’t match. It’s necessary to double the number of edges on the left so both have four edges. This needs to be done with all quads and without changing the periphery of the patch. Once that’s done filling in the hole is straight forward as shown in the third image. This solution can be subsurfed with no issues as shown in the last image. I hope you come by sometime and get a chance to see this. Mesh0s Mesh1s Mesh2s mesh3s

nice fix :slight_smile: