Created attachment 667193 [details]
This is a new ebuild for sci-mathematics/sfcgal-1.3.9 (released Oct 1). I believe this belongs in sci-mathematics (and not geosciences) because it is strictly a mathematical wrapper OGL SFA compliance for an existing sci-mathematics library.
It depends on an updated sci-mathematics/cgal (ticket #750233) and obsoletes bug #653086 which appears to be an abandoned attempt to add a more complicated older version of this package 2 years ago. Many optional features (such as the optional Qt4 viewer) have been removed since and the codebase dramatically cleaned up.
Optional OpenSceneGraph support is provided through the "osg" USE flag which many other packages with optional OpenSceneGraph support already use.