[freebeard]

Open VDP
It seems like this is limited to animation.
They're not measuring anything.
Their algorithms have been cribbed from actual kinematic phenomena recorded and stored in front a green or blue screen.
'Air' cannot be 'observed.'

OpenVDB
It's a physics engine used in animation
They're not measuring they're generating data.
It's computational. no green screen.
"air' can be described mathematically.