You cannot merge (using “Merge Visible") a layer with the base mesh layer (the original layer that exists when you first create/import an object). Currently the only way to do this is with “Flatten” but this merges all of the layers into the base layer. I believe somewhere in the mudbox documentation it states that a layer can take up almost as much memory as the base mesh layer. If I liked the changes in a layer and wanted to merge it into the base mesh layer so that I can free up the memory that was being taken up by that layer then I currently have to flatten all the layers, thus losing all of the other layers that I may still wanted to have kept.  If I could use “Merge Visible” to selectively merge newly added layers into the base mesh then this wouldn’t be an issue.

It seems like it shouldn’t be too difficult to allow merging layers with the base mesh layer since you already allow merging layers into the base mesh layer with the Flatten command.  I understand that the base mesh layer is a special layer so maybe you could just make it so that in order to merge layers, the user has to have the base mesh layer selected.  Maybe bring up a warning box if the base mesh layer isn’t selected.  Better yet, just have the command automatically detect if the base mesh is one of the layers the user is trying to merge and merge all of the other layers into it and rename it to be have the name of the layer that was selected when the Merge Visible command was called.

Thanks for reading.