How to create/display a static voxel_grid map?

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I've searched quite a bit, and to no avail, for a modern, minimal example of creating a static voxel map and displaying that map in rviz. Most tutorials have incomplete steps, or aim at map creation within the whole navigation environment. Without sensors or navigation infrastructure, I wish to load a pre-existing global voxel map and display that in rviz. Is 3D map creation and publication possible without providing sensor sources? I was able to do this through map_server in 2D by providing a BMP file.

This video is a nice example of what I'd like to display, but they're clearly using sensor input.