How do I correctly reduce geometry on part of a mesh?

Question

Good afternoon, I already know that there are easy ways for reducing face count for the entire model. However I am trying to find a way to reduce faces only on specific parts of my mesh while keeping it deformation and rendering-friendly for animation.

From youtube tutorials I managed to figure that all I can do is to manually dissolve edges and verices and create new edges to form triangles to connect large faces with the smaller ones as follows (I must avoid faces with more than 4 vertices as far as I know):

Is this the "good practice" way of character modeling? Will the model UV unwrap, animate and render properly afterwards? (I know the example mesh from the screenshot is not a character, but I will need to create one and sculpt details on parts of the character). Or is there an easier way of doing this? Please help.

Answer 1

You can try the decimate modifier. It can take a vertex group so first add the faces you want less detailed into a group, then select it in the modifier.

Answer 2

Maybe try building it from scratch with simpler geometry. You can do with a 5-sided cylinder, but I like using powers of 2 (you need more than 4 sides): Extrude an 8-sided cylinder into roughly the same profile and mark the hard edges as creases using Edges -> Mark Sharp. Then apply a subdivision surface modifier to smooth it round. You can disconnect the middle portion from the ends before applying the modifier by selecting the faces you want to be their own object and tapping the P key. You will still have to double the edge loops where the pieces meet somehow, but your work will be isolated.

There are a couple of reasons to avoid triangle faces: They can cause weird deformations during animation if they break edge loops. But even if a model is not going to be animated, you can get weird shading effects if the diagonals and/or interior angles of adjacent faces are significantly inconsistent. Further (and most glaringly), you don't want inconsistent surface curvature by retopologizing a ring of quads into a ring of sawtooth tris. None of that means it is bad to EVER use tris, only that you have to be careful how and where you use them.