Solved: Subdiv smoothing across separate meshes

jonboris · ‎12-14-2014

Hi, I'm running into some workflow issues while creating mesh assets for an avatar system.

The character is broken up into separate meshes for the legs, body, hands etc, and all bound to the same master rig.

I want to be able to use smooth mesh preview to bake out good quality ambient occlusion maps for use in texturing (because the base models are so low-poly I often get artifacts around sharp crevices like the armpits and crotch).

The problem is, I can't figure out a way to get the smoothing across the separate mesh parts. For example from the arms mesh to the feet mesh, resulting in hard edges between the 2 body parts which is not what I want.

I've attached an image to show what I mean.

The only way I can currently think to do this is by temporarily combining the meshes, merging the seams, hitting smooth preview, and baking... but we're going to have hundreds of assets soon and this method would be very slow.

Please, if anyone has experience doing this stuff I'd love some tips!

jonboris · ‎12-14-2014

hmm, well I got it working!

I use some of the techniques described here:

http://forums.autodesk.com/t5/modeling/combining-2-half-spheres-to-look-like-one/td-p/5435261

1) Start with the 2 meshes joined together, complete with any edge softening you want to happen.

2) Now, to get subdiv smoothing across the 2 meshes later, we need to split a face loop using the edge loop tool. This will give us 2 face loops with matching face normals, which means they will smooth perfectly.

Note: I've no idea how you'd do this across a contantly curving surface like a sphere without leaving a slightly flat bit across the split! It works best on stuff like arms and legs.

3) Duplicate the mesh and hide the original

4) Select all the faces up to the edge loop you just made and extract them, so now you've got 2 separate meshes.

5) Delete the history on your new meshes to avoid any weirdness.

6) Now, select the original mesh that you hid, and shift-select one of your separated meshes... and open the transfer attributes options.

7) Deselect everything except for vertex normals, set sample space to "world" and search method to "closest point"

😎 hit apply, and repeat from step 6 for the other separated mesh.

9) Ta daa! the 2 separated mesh parts will now smooth seamlessly from one to the other, both in terms of vertex normals and in terms of subdivision. (Select both meshes and hit "3" to test this.)

10) If your meshes go all weird and blotchy after transferrring attributes, try playing with the sample space and search method in the transfer attributes panel and try again.

I hope this helps anyone trying to achieve smoothness across separated meshes.