Original Post
I am trying, hardly, to calculate lightmap for different objects. Obviously, using simple shape such as cube or plane does not make lot of trouble. But as soon as I try to use sphere...it's really different. Currently, the cut is seems to work, all the triangle of the sphere are stuck by group(with same smooth group and small angle of difference between face). But when I calculate lighting, I have different graphical artefacts precisely where two edges of different groups are colliding. Moreover, faces have their UV axes not always along world axes. The worst example is the sphere! Some faces have their UV at 45°. It seems that the best way is to cut each face...but of course it's a bad idea.