I wrote a 3D viewer for Parasolid files to enable our customers to preview assembled models of configurable components. Given the high per-seat licensing costs associated with using Parasolid libraries, this included implementing a tessellator for Parasolid XT format boundary representation solids. I used jMonkeyEngine to display the resulting triangle meshes in our Swing application, and integrated the sunflow raytracer to provide high-quality rendering.
I integrated the D-Cubed Constraint Manager library into our Java application via JNI, and provided an easy-to-use wrapper as a part of the CLIK library. Complex 3D relationships can be expressed as CLIK rules, and the resulting solutions obtained from the D-Cubed libraries can then be displayed in the integrated 3D Viewer or printed as reports.