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Table of Contents
Combining (merging) multiple models into a single .binvox file
This is a fairly popular use case, for which I had promised to write a tutorial many years ago.. 
An example 3D model with multiple components
I constructed the example from this 3D model on Sketchfab and a sphere,
combined using the blender 3D modeller (https://www.blender.org):
Splitting the 3D model
In blender I selected the “heart” sphere, deleted it, and saved the puppet as an .obj file (File → Export → Wavefront (.obj), then select Z as the up axis). Next, Edit → Undo, and the same step to save the sphere to an .obj file.
The resulting files: puppet.obj and heart.obj
Voxelizing both models in the same coordinate system
The goal is to voxelize them such that after merging they end up in the same spot relative to each other.
For this we need to determine the smallest bounding box that contains both models. Since in our example the “heart” is inside the body, we can use the bounding box of the puppet.
binvox determines a model's bounding box and prints it to the terminal:
- merging the resulting binvox files
- visualizing the merged binvox file
