The video below demonstrates 3D data integration of terrain, roads, threes and buildings in a 3D voxel model. All source data are different, but finally they are integrated in one topologically valid model, resolving all overlapping issues which result in mixed voxels. The validity of the model is ensure with a set of operations on an octree, which is managed in database SQLite.
More information about the octree and the operations is available here:
Gorte, B., 2023, Analysis of very large voxel datasets, International Journal of Applied Earth Observation and Geoinformation, Vol. 119, May 2023, DOI: https://doi.org/10.1016/j.jag.2023.103316