# Control shape keys with drivers to the speed of rotation

I have this scene with a probe and 5-way RCS thrusters. Its rotation is awkward so I don't want to manually animate the thrust of the RCS but instead I want to use drivers that control the shape keys by how fast the main probe is rotating. The shape keys control the thrust of the RCS. I'm very new to drivers and I've watched a few tutorials on them but can't find an answer. It might be really simple but as I said I'm new to them.

A value of 0 equals full thrust and a value of 1 equals no thrust.

• i don't see shape keys in your blend file... Commented Jun 3, 2023 at 11:33
• Does this answer your question? Possible to use object speed/acceleration as driver variable? Commented Jun 3, 2023 at 12:14
• @Chris You need to select the long cylinders coming out of the thruster block, it has the shape keys. Commented Jun 4, 2023 at 2:45

By using the vertex parenting technique from here:

Passing GeoNodes attribute to Shader frame offset

As well as the new Simulation Nodes feature in Blender 3.6β, you can access speed (and even acceleration with a slightly more elaborate setup), by creating a new cube, ⭾ Tab, M, A Merge at Center to have just one vertex, and adding a geonodes setup like this:

Now the parented empty's position is the velocity of the Cube:

And accessing the empty's position in a driver should be straight-forward.

## Acceleration

Notice that in this case I converted the acceleration to a direction-less scalar, just to show this is also possible. In order to read it in a driver, just access any location component ($$x$$/$$y$$/$$z$$) of the empty:

Before B3.6 it can be achieved in various other ways, either using Python for a driver:

Possible to use object speed/acceleration as driver variable? (I've seen tons of similar questions here)

Or using Python for a simulation - or using a simulation in another way, both explained by me here:

How to create a simulation in Geometry Nodes pre 3.6?