In particular, the j3d-core-utils project provides additional functionality under a different license, which is needed in some circumstances by core Java 3D. Thus, historically, these two projects have been co-dependent. This interface breaks the circular dependency by using Java's service discovery mechanism: if j3d-core-utils is present on the classpath, its GeometryServiceImpl will provide the functionality defined here. Or if not (i.e., no suitable GeometryService implementation can be discovered and instantiated}), then the Java3D core will fail as gracefully as possible.