Outcast's graphic system was particularly interesting because it wasn't just voxels: It was a voxel system for the landscape and polygons for actor-class things

Outcast's graphic system was particularly interesting because it wasn't just voxels: It was a voxel system for the landscape and polygons for actor-class things and structures (since most voxel implementations can only render heightmaps and thus are perfect for landmass features if little else).