K-3D is free-as-in-freedom 3D modeling and animation software. It
features a plugin-oriented procedural engine for all of its content,
making K-3D a very versatile and powerful package.

K-3D excels at polygonal modeling, and includes basic tools for NURBS,
patches, curves and animation.

Optional dependencies:

graphviz
gtksourceview
libgnome
OpenCASCADE
