I have a simple low-poly model.
On the right it looks smooth, but as the shape progresses to the left, it becomes increasingly creased.
There are no sharp edges, creases, or weights defined. Auto-smooth is inactive, but turning it on has no effect to remove the creases, no matter what angle values I use.
Why is it transitioning to sharp edges, and how do I make the shading completely smooth without adding triangles?
What’s your wireframe look like? I’m guessing you have some long skinny triangles, poor geometry will give that exact issue
Also, I have plenty of other shapes with long quads that don’t have this issue - but the opposite edges are more similar. So it happens when quads have very different opposite edges?
I have tried to reproduce the problem, and yes, it is true. It happens even with quads. Never had this problem myself before and it can be reduced by using the subdivision modifier, but would still be interested in what’s going on there as well, or how to avoid it. (Tested with Blender 2.79, 2.83 and 3.12, no modifiers, sharp edges, auto smooth, ect.).
Shading a cone in 3D is always a problem and it’s not limited to Blender.
Something you can do is make the tip a very small flat face (a true pointy end can never be properly shaded) and add edge loops that get increasingly closer near the tip.
If you needed to make a truly perfect looking, geometric representation of a cone, that could be done by leaving the cone in flat shading and using enough edges that you can’t tell.
The images I posted do end in a flat face (click to expand the images) so the pointy end is irrelevant.
Adding more loops fixes it, but increases the triangles by 300% so I’m not sure that’s ideal, but it looks like that’s the only thing I can do.
Well, there is an alternative, which is to bake a normal map from a higher res cone. But, unless you were going to use a normal map anyway, the extra polygons are actually cheaper and simpler.
Honestly, polygons are overall very cheap and I can’t think of any use case these days that would require using that few polygons. So I say you don’t have to be scared about your polygon count if you are merely in the hundreds of triangles (even video games these days often use tens of thousands for each object).
