This code uses the Panda3D game engine in order to create synthetic optical flow from moving 3D objects

pip install panda3d scikit-image
python panda.py

# You can visualise the saved optical flow maps with ffmpeg's ffplay
ffplay -framerate 24 -i "out/%05d_flow_vis.png"

Showing original frame, visualised vertex coordinates, and visualised optical flow:

Or for a bouncing cube:

python cubeortho.py .5