As far as I know, you only use UpdateNormals when you have manipulated with the triangles or vertices of a mesh..
you don't need to do it on models you have exported from a modelling package..
UpdateNormals normalizes the normal vectors of every triangle, according to the vertices the triangle's connected to.. this means that the face will point in the right direction.. (other wise it would be invisible)
you don't need to do it on models you have exported from a modelling package..
UpdateNormals normalizes the normal vectors of every triangle, according to the vertices the triangle's connected to.. this means that the face will point in the right direction.. (other wise it would be invisible)