I’m modelling a series of gears, and so I want to drive the rotation of one gear from that of another, which in turn is driven from another, etc. I have added an F-curve driver to the second gear, to drive its rotation from the first, and that works just fine.
But when I add an F-curve driver to the third gear to drive it from the second, nothing happens. I get this error message “Error: driver has an invalid target to use”. Does that mean I can’t chain the drivers in this way?
Why not also drive it from the first gear if they are all connected.
http://www.blendercookie.com/2009/08/13/animating-a-gear-train/
Yes, I could do that, but there are a lot of gears and the ratios are different (it’s an orrery), and I can’t face all the calculations!
Can anyone say if this is a bug, or my lack of understanding of how drivers work? This is the first time I’ve used them, and I haven’t got the hang of them yet.
In the attached .blend, (for blender 2.54) the object cube rotates 360 degrees in 40 frames. Cube.001 rotates 180 degrees in the opposite direction based upon cube’s rotation. Cube.002 rotates 90 degrees in the opposite direction of cube.001 based upon cube.001’s rotation. I didn’t create gears, I just used cubes, but yes, cube.001 is driven by cube, and cube.002 is driven by cube.001. See for yourself, rotate cube and observe the behavior of the others.
HTH,
Randy
Drivers.blend (428 KB)
I’m not quite sure what I was doing wrong, but I was using a much too complicated method to set up the drivers. Your example showed me a simpler way to do it, which works like a dream.
Thanks for going to the trouble to set up that example for me. It was extremely helpful.
And indeed nice to see, how simple it is (and playing with the degree of the polynomial is super too!)
Thanks for showing the example!