In ‘Vangers’, the map is made and rendered with real voxels. Now that's some shit: https://www.youtube.com/watch?v=P9R7QJ5Sh1o
Simply having blocky cubes as units is just not the same, at all.
> All the worlds in Vangers were created with Surmap A.R.T., K-D Lab's proprietary terrain editor, and the accompanying voxel-polygonal technology.
How do you figure you can render a voxel without any sort of polygon?
IIRC Vangers could work without 3d acceleration (in the original release, at least), and possibly did not require it at all. Polygons are used for vehicles and items, and there are maybe fifty polygons per a vehicle. You'll notice also that the depth of the voxel terrain is quite limited, as is the main view dimensions.
Also, the game engine is open-sourced, though it's the updated re-release: https://github.com/KranX/Vangers
The first, as is the case with this, is moreso on the data structure side of things, in which a voxel is like a point in a point cloud, but the point cloud is fixed to a 3d grid. The meshes can be anything, but cubes are the most common, and they are almost always polygonal.
The second is, as you describe, a fundamentally different rendering method using "3d pixels" instead of polygons. These kinds of voxels almost always use the same data structure above as well, but as you say they aren't polygons.
Strange we ended up with the same word for both, unless I'm mistaken