Help needed. I am using Blender 2.79 - I have a dress that I modeled and then unwrapped in UV layout. The problem is that I never added any material zones. What I would like to do now is add materials by UV island without having to try to select all those proper polys in 3d menu. Is there a way to add material zones by uv? Any help is appreciated!
One way is to use Select Linked command in the viewport and constrain it by seams.
If there aren't seams already on the mesh choose UV > Seams From Islands in UV editor (when UV map is visible).
With seams available select a face of the mesh and press Ctrl+L (or L if mouse cursor is over the mesh) while in 3D viewport. In operator options (F6) choose Seams.
Now there will be selected only that part of mesh geometry corresponding to one of the islands.