Very often when i do a loop cut it makes a bigger cut than i want. For example, i might just want to extrude a part of the top of model, but the loop cut will go all the way around the bottom and back up the other side.
Before, as i was still pretty green about topology, i found this annoying because it was (in my mind) creating unnecessary topology and increasing my poly count.
But now i’m kinda realizing that actually it’s good because the loop cut ensures that i retain quads, which is good topology, right?
So my actual question is: is this a good way to think about it, should i not worry about those extra polys and does a loop cut always only want to create quads or will it also create triangles?
So, this is what you call a tradeoff. There are pros and cons to using loopcuts, and it depends on what you want, and what your poly count budget is.
Whenever you make a loop cut, you are adding “more” polies to the mesh, so that you can do extra things to it. Think of loop cuts as a stepping stone to your next action. You need them, because without them, your object will remain a rigid, and very difficult object to work with later on.
Loop cuts are useful for:
Increasing the subdivision count in one (or more) axes so that the object can be bent or twisted
Increasing the poly count so that you can extrude (inward or outward) certain areas while leaving other areas unaffected
Enables you to deform your mesh slightly so that you can give it an worn look (i.e. a wavy sword rather than a straight sword)
So, with that said, the only way to know if your object is going to create extra triangles is if your mesh’s topology has a lot of triangles or ngons (polies with more than 4 sides). If your mesh strictly has quads, most of the time you’re going to be fine when adding edge loops (in other words, you won’t have to worry about triangles being created). The only time adding an edge loop to a fully quaded model is an issue, is when the topology is spiraling, or making sharp turns which causes the edge loop you’re adding to change directions and go (for example) north rather than east.
There are a few ways to know if adding a loop cut causes you to have problems with poly count.
It exceeds your poly count budget. In other words, you have a stated goal of say, 5000 polies, and the loop cut causes your mesh to become 6000 polies. The only way for you to know if this is a problem, is if the device you’re putting it on doesn’t have the available GPU power to display this mesh at a performance level you want, or is required by your employer.
Adding extra loop cuts makes the model have redundant topology, which actually makes it harder to work with later on. (i.e. Too much of a good thing can be bad) (i.e. Why add 1 loop when you can add 5000? Wee!)
Your gut tells you this is wrong.
My advice is to experiment. You will learn through trial/error what works and what doesn’t work. 5 years from now, you will go back and look at your early works and think, “wow, that was done extremely inefficiently, I can do that far better now”. And sometimes the journey of making mistakes and learning from them is more important, than knowing everything beforehand and not knowing how to even begin.
Its gets complicated and basically you will end up using re-topology if you want to optimize your mesh at the end. If you are creating a game asset and want a lower poly count though i would definetly try the new quad remesh tool or the voxel remesh. Easier and faster than manually re-topoloy which is really only necessary (apparently) for meshes that are going to be deformed, especially things like character faces.
Subdivision surface modified will always make quads so I wouldn’t worry about quads as much as are those extra edge making the rest of your model ugly. They may also get in the way of things you want to do in the future to other parts of your model.
I try to be very cautious about run away loop cuts because more often than not they are an issue.
When you get really really skilled at poly modeling you will know exactly the geometry wanted even before making the first polygon. When this happens if you get to a point where you are happy with the geometry already there you will know how to leave it alone and not add more to it. Having the loops in the right place is the most important thing with geometry, so it’s a good place to start when thinking how to model anything. Drawing a 2D picture of the object and drawing where the loops are going to be can be a huge help when starting off. Maybe even draw some polys in there as well. It is hard to think polygon. If the vision you drew up in 2D included an extra loop cut there it is ok. If not try follow the plan. If the plan is not working redraw the plan so it works. You could also just hard surface model it any old way you want and use Quad Remesher to give something better. A human that knows there stuff can still do better than Quad Remesher, but Quad Remesher does good enough most of the time.
