In the OBJ spec ( http://www.martinreddy.net/gfx/3d/OBJ.spec ), in the section labeled "Grouping" -> "Syntax", the structure of the "g" group statement is defined. Though this statement allows multiple names on a single line, it is unclear whether there must be at least one name on the line. However, the examples don't show any "g" group statements with no names. So, let's be conservative and not write out a "g" group statement that doesn't have a name. These empty "g" statements were prompting an error message from the three.js OBJ loader code.
In the OBJ spec ( http://www.martinreddy.net/gfx/3d/OBJ.spec ), in the section labeled "Referencing groups of vertices", there is no support for allowing a trailing slash with no valid vertex normal reference at the end. This commit modifies the vertex reference output code to prevent this behavior, as it has been causing compatibility issues with other software that parse OBJ files.
Alexander Gessler
Kim Kulling
Nathan Morse
Judith Hartmann
Marshall Hahn
aramis_acg