This is an option to optimize the file size of the converted FACT.

In some OBJs each polygon of a mesh is stored with its individual points. Eventhough adjacent polygons share the same point coordinates they are stored as different entries. Join Vertices finds all double assigned points and joins them. This results in smaller FACT file sizes.

Note: In some very rare cases this option can cause troubles with morph targets. If you discover any incompatibility in morph targets in EI unchecking this box should fix the problem.