How to reduce mesh vertices to obtain homogenous density while maintaining manifoldness

Question

in Blender 2.79 I used to have a technique to make meshes have an even/homogenous distribution of vertices. I would start to increase the number of vertices (if necessary) using the "subdivide" or the "remesh" tools. Then I would apply a "remove doubles" (in 2.79, now it's called "merge by distance") with a distance that corresponds to a density I wanted.

The issue is that using the "remove double" would work pretty well in version 2.79, however in recent versions (e.g., 2.92) using the "merge by distance" tends to produce a lot of non-manifold faces.

This can be demonstrated just by using the default cube scene:

1. Start with the default scene cube
2. Apply a default settings "voxel remesh" (usable from object mode, not from edit mode)
3. Apply a "triangulate faces" and a "shade smooth" (that will help visualise the issues in the next step)
4. Do a "merge by distance" at 0.2m
5. Deselect all and then "select all by trait" - "non-manifold"

As it can be seen, the mesh becomes all messed up.

For comparison here is the result of the equivalent operations in 2.79:

Is this a bug? Is there any workaround for this?

Is there a better way to achieve homogenous vertex density while maintaining manifoldness?

Thanks.

Answer 1

Well, I think I may have found a nice way to solve my own issue using the remesh tool itself:

Using the "QuadriFlow Remesh" with the "Edge Length" mode set to the desired value, or using the "Vertex Remesh" with the "Voxel Size" set to the desired value, produces pretty and homogeneous meshes while maintaining manifoldness.

Example:

1. Starting with a UV Sphere, which has a vertex density not so homogeneous

   

2. Apply a "QuadriFlow Remesh" with the "Edge Length" mode

   

3. The mesh gets a more homogeneous vertex density

   

• Using the "Vertex Remesh" with the "Voxel Size" set to the desired value

  

• will result in an also nice mesh:

  

The other remesh settings, may also produce nice results.

(Anyway, I still think that the merge by distance has some kind of bug, or else it must be used carefully. Edit: it's not a bug, it's expected behavior)