Coin3D
Integrates seamlessly into the Qt development environment.
Coin3D is a high-level, retained-mode toolkit for effective 3D graphics development. It is API compatible with Open Inventor 2.1. Save developer time using powerful software modules for real-time 3D visualization, for it features: high-level, retained-mode API for maximum programmer efficiency, integrates seamlessly into the Qt development environment, fully backward compatible with Open Inventor 2.1. Full access to source code, C++ API, with bindings for Python, BSD 3-clause license permitting free commercial use.