Ayam is a free 3D modelling environment for the RenderMan interface.
It features RIB export, CSG (all RenderMan primitives supported), and NURBS modelling.
Ayam features at a glance:
RIB (RenderMan Interface Bytestream) export and import.
Support for NURBS curves and (trimmed) NURBS surfaces, Boxes, Quadrics (Sphere, Disk, Cylinder, Cone, Hyperboloid, Paraboloid, and Torus), CSG, MetaBalls, Patch Meshes, Polygonal Meshes, and Subdivision Surfaces.
NURBS modelling includes normal and interpolating curves as well as extrude, revolve, sweep, birail, skin and gordon objects with caps, holes, and bevels.
Custom objects that may freely implement their representations (using OpenGL and RIB) and even small GUIs to edit their type specific parameters may be written by the user and dynamically loaded at runtime.
Cal3d is a skeletal-based 3D character animation library written in C++ in a platform-/graphic-API independent way. Originally designed to be used in a 3D client for Worldforge, it evolved into a stand-alone product which can be used in many different kinds of projects.