Hi, I have a UV unwrapping problem. When unwrapping a model I am working on, part of the ship stays white and it will not let me edit it. The rest unwraps OK and can be textured. I have checked that the faces concerned are not treated as separate objects and that the whole model is selected before unwrapping. Any clues or ideas how to fix this please. Otherwise my Acclamator-class assault ship will look rather odd...
Sounds like a case of reversed Normals. Before I unwrap a model, I always go into Texture Paint mode to check if the Normals are reversed on any part of the ship. If the Normals are reversed, whole faces of the ship will seem to not be there, and nothing can be done with them in that state. What has happened is the outside surface, the part you have been forming to whatever shape you intend, has faces that for reasons unknown to me are flipped inside out, so that you can see through it. That's the way it would appear from the inside of the ship, if the Normals were correct. You have to select the vertices surrounding any area that show white, go to Mesh on the bottom tool bar, left click on that and pan up to Normals. You will see three options, but the one you want is "Flip Normals". That has to be done in Edit Mode. Be careful to select only the face that is showing white, because if you also select a face right next to it that isn't reversed to begin with, you will then flip that face inside out while flipping the intended face right side out.
You can still do this, even after unwrapping, but you need to put the unwrap aside for a while, return to Edit Mode, and do what I described above. Once more, you can check on which faces you want to select by just going back and forth between Texture Paint Mode, and Edit Mode. Texture Paint Mode will show what normals are flipped, as you will be able to see through those faces that are flipped inside out, and need correcting. Selecting the flipped face in Edit Mode to flip it to Normal as described above, and then rechecking in Texture Paint Mode will eventually get the whole model right side out, and THEN you should be able to work with it in unwrap. Does that make sense?.