UV mapping is a technique used to “wrap” a 2D image texture onto a 3D mesh. “U” and “V” are the names of the axes of a plane, since “X”, “Y” and “Z” are used for the coordinates in the 3D space. Every point in the UV map corresponds to a vertex in the mesh. The lines joining the UVs correspond to edges in the mesh. Each face in the UV map corresponds to a mesh face. These are 2D coordinates, which is why they are called UV, to distinguish them from XYZ coordinates.
Why do you need UV mapping?
It is generally necessary if you wish to texture your object very accurately, those coordinates dictate textures placement either in Blender itself or Unreal Engine 4.
When to start
You want to unwrap when you feel your mesh is complete with respect to the number of faces it needs to have. If you do add faces or subdivide existing faces when a model is already unwrapped, Blender will add those new faces for you, but you may need to do additional mapping or editing.
A good habit to make sure that the transformation value are applied. Applying transform values essentially resets the values of object’s location, rotation or scale, while visually keeping the object data in-place. The object origin point is moved to the global origin, the rotation is cleared and scale values are set to 1.
|MENU:||Object ‣ Apply ‣ Location / Rotation / Scale / Rotation & Scale|
Blender offers several ways of mapping UVs but for our needs we going to look closer to:
- Manual Unwrap,
- Smart UV Project,
Create UV maps in Blender 3D
Unwrap is more precise method which allows to mark seams to make them as less visible in the scene as possible. In some cases (like character) you may need custom uvs. Imagine how to wrap piece of paper on your object. Once your UV Maps are created, make sure UV0 is selected (UV1 is for light map).
Smart UV Unwrapping
This is very quick option to use and is working very well in many situation. Smart UV will automatically unwrap any object/mesh and you can save tons of time. Keep in mind this method may produce seams in areas you don’t want to.
See also more information about other mapping types.