To cut a long story short I want to have overlapping UV islands on my the primary UV layer of my Skeletal Meshes. The primary reason I want to do this is to save time and texture space. But I am concerned that overlapping UVs on my Skeletal Meshes is going to return lighting issues and I want to find out if there is a way to over come this, or if the way I want to over come it is possible / workable.
First a little more detail to explain exactly what I am trying to do: Say for example I am modelling a Sports car and this Sports car is completely symmetrical. That is the left side and the right side of the car are identical, same colours, same normals. So when I UV unwrap this Sports car, lets say I have a large UV island for the right passenger door. So what I want to do is unwrap the left passenger door and place it directly on top of the right passenger door, so that they share the same UV space. That way, I save literal space in the texture and it also means I don’t have to paint two identical doors on the texture. This seems like a great time saving technique to me. But is it going to cause lighting errors?
Now, I am aware that with Static Meshes there is a simple and effective work around for this problem. Inside Blender 3D it is possible to give a mesh object multiple UV layers. So for example I can give the mesh object 1 UV layer called “Diffuse” and unwrap that layer to the textures, diffuse, normal etc, with overlapping UVs. Then I can assign an additional UV layer to the mesh object and call it for example “Light” and perform the UV unwrap again but this time with no overlapping UV islands. Then inside Unreal Engine 4, I can tell the engine to reference Lightmap Index “1” instead of “0” and the engine will use the “Light” UV layer for calculating lighting so that no errors occur due to overlapping UVs.
So my question really is this: Is it possible to use this same technique with Skeletal Meshes? To give my skeletal meshes an additional “Light” UV layer and some how tell UE4 to reference that second UV layer (without overlapped UVs) for lightning calculations.
Is this possible and if so where and how would I tell UE4 to reference the 2nd UV layer? Any tips or advice on these topics would be gratefully received. Thanks!