The Great Mouse Launch: Part 3 – Using Drivers to Connect Size to Mass

Continuing on with the next phase of our Great Mouse Launch tutorial, it’s important to understand how mass is going to affect the simulation.  In the real world, when something gets bigger it will probably end up weighing more.  Except me.  I weigh the same, no matter how big my tummy gets.  That’s my story, and I’m sticking to it.

And yes, these pants fit fine, thanks for asking.

Anyway, in order to set up this relationship where the scale of our object will affect the mass, we need to use Blender’s Driver system.  Drivers are like Maya’s expressions + set driven keys.  But… a bit more confusing.  And powerful.  And confusing.

So in this tutorial, I introduce the concept of drivers and show how to use scale to drive the mass of a rigid body object. And remember to go to Preferences and enable ‘Auto run Python Scripts’ to get the drivers to work since it is disabled by default. Enjoy!

Jason Schleifer
Jason Schleifer
Jason and his mad scientist eyebrows have been pushing the boundaries of CG animation and sharing his knowledge for nearly 20 years. Widely recognized as an industry leader and mentor to hundreds of animators, Schleifer, formerly of Weta Digital and Head of Character Animation at DreamWorks, now works as Head of Content and is a co-founder of Nimble Collective.


  1. Very cool… I’m impressed with how fast you are learning Blender. And it’s interesting that you went really quickly to the dynamics. Is it something that you often use in any 3D software?

    It’s true that the drivers in Blender are bit tough to get at first but they are so useful!

    Looking forward to see the big launch!!!


  2. Thanks Mathias! I love learning new tools, and sharing the learning experience with others is the best way force myself to learn quicker. 🙂 I didn’t use dynamics a lot in other packages, but it’s a good way to see quick results. In my spare time I’m learning more about the animation process in Blender. 🙂 looking forward to sharing that and rigging!

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