Volpack is a software library for fast, high-quality volume rendering with this features:
* renders data sampled on a regular, three-dimensional grid.
* supports user-specified transfer functions for both opacity and color.
* provides a shading model with directional light sources, multiple material
types with different reflective properties, depth cueing, and shadows.
* produces color (24 bits/pixel) or grayscale (8 bits/pixel) renderings,
with or without an alpha channel.
* supports arbitrary affine view transformations.
* supports a flexible data format that allows an arbitrary c structure to be
associated with each voxel.