...CGAL features a great range of data structures and algorithms, including Voronoi diagrams, cell complexes and polyhedra, triangulations, arrangements of curves, surface and volume mesh generation, spatial searching, alpha shapes, geometry processing, and many more. The use of these result in beautiful, visually complex and accurate representations.
Yocto/GL: Tiny C++ Libraries for Data-Driven Physically-based Graphics
...Simple shape data structure, utilities for manipulating triangle meshes, quads meshes and line sets, computation of normals and tangents, linear and Catmull-Clark subdivision, procedural shapes generation, ray intersection and closest point queries. Ray intersection and closest point queries of triangle meshes, quads meshes, line sets and shape instances using a two-level bounding volume hierarchy. Path tracing of surfaces and hairs supporting area and environment illumination, microfacet GGX and subsurface scattering, multiple importance sampling.
MDSTk is a collection of 2D/3D image processing tools aimed at medical images. It contains routines for volume data processing (3D filtering, segmentation, etc.) as well as fast low-level vector graphics library for surface and tetrahedral meshing.
MDSTk has been forked by 3Dim Laboratory s.r.o. to provide better support and further push its development forward. Please check VPL (Voxel Processing Library) project available on Bitbucket (https://bitbucket.org/3dimlab/vpl).