I have problems with the topology of a polygon I’m trying to create.
I need to add some support edges to prevent it from becoming too smooth with the subsurf modifier, but I have some strange results with the topology I used to handle the concave areas.
Here is a convex corner. I don’t know if the topology is correct, but it doesn’t present any problem:
I tryed something similar in a concave area, but cutting through one more loop:
When the subsurf is applied, the result is really bad. I really can’t understand why it is smoothed like this. It seems like there are two overlapping meshes. The topology looks ok to me and it’s all quads:
“1” is how I’m trying to do the polygon as en exercise. “A” is the corner I have problem with and I’m trying not to cut to point “B”. In this particular case I think I could, but I’m trying to learn how to handle a concave corner on its own.
“2” is another topology I came up with, that could work better in this case, but it’s something I’m trying to avoid.
The Subsurf won’t be able to handle all those tiny faces. In case of original file, look at what happens in Object mode, with Wire and Draw All Edges options in Properties Editor > Object tab turned on:
Vertices from the corner weren’t smoothed that much preserving their almost original shape. They meet ones which were subdivided and smoothed much more by modifier; because of that they start to overlap and create intersecting geometry and z-fighting.
To avoid that create such topology that will allow edges to follow initial from of the object, its corners etc. In this case it’s easy to do with beveling edge loops in the corners. Subsurf doesn’t like sharp faces. If you plan to make a corner, create it from 2 edge loops instead of one:
Note: to achieve that I dissolved part of vertices in the corners. I didn’t use Bevel modifier rather than Bevel operator in Edit mode with Ctrl+B in order to have more control over amount of effect and resulting faces.
