# What is the difference between passive and non-dynamic rigid bodies?

A rigid body can be either active or passive, and an active rigid body can be dynamic or not:

The documentation says about the passive type the following:

Object is directly controlled by animation system. Thus, this type is not available for Rigid Body Dynamics.

Enables/disables rigid body simulation for object.

I see no difference between the two. As far as I can see, both of these mean that the object is not moving, but still participates in collisions.

Note that I know that there is already a similar (unanswered) question...: rigid bodies: passive vs not-dynamic

... but I decided to ask again, because I could not reproduce the scenario in that question (extruded planes behave for me the same as non-extruded).

EDIT As f59838 answered, there is a tutorial, where Andrew "Blender Guru" Price says that "We want our chain to swing, so we need the top link of the chain to be stationary. Select it then go to the Physics panel and uncheck Dynamic. This is different to Passive, because it’s still using it’s Mesh collision data but it won’t move."

I think this explanation is not correct, because passive objects also can have a Mesh setting for the collision shape. It is true that in this special case (toruses) it does not work - after a few strange movements, they fall - but this seems like a calculation error. In fact, if you double the Steps Per Sec in the Scene/Rigid Body World, the toruses won't fall (although the movements are still strange)

So yes, there is some difference, but it is not what Andrew said.

• It seems to me that setting object to "Passive" will result in higher performance computations but the accuracy will be lower. If you find that dynamic objects do not interact correctly, you have to set the problematic objects to Active + deselect Dynamic. I don't know any official documentation for this difference, though. Tested with Blender 2.90. – Mikko Rantalainen Oct 18 '20 at 15:37

here you can find the subtle difference:

https://www.blenderguru.com/tutorials/quick-tutorial-make-a-wrecking-ball-with-rigid-body-physics/

It says:

"We want our chain to swing, so we need the top link of the chain to be stationary. Select it then go to the Physics panel and uncheck Dynamic. This is different to Passive, because it’s still using it’s Mesh collision data but it won’t move."

• Thank you, but I don't think that this is the answer, because passive objects also can have a Mesh setting for the collision shape. I'II edit the question to explain what I think in more detail. – WannaKnow Jan 7 '17 at 20:25
• sounds reasonable - so there is a difference in calculation - maybe check the source code to get to the bottom of this. – adegner Jan 7 '17 at 20:55
• thanks for pursuing this, WannaKnow. I'm glad others find the fine distinction puzzling (I feel less stupid now). seems to me there must be some reason why the two options (Passive/Active vs Dynamic on/off) were provided in the first place... unless one of them is a legacy feature that someone meant to remove but never got around to it? – Tazling Jan 8 '17 at 21:19
• This is an interesting answer, but, not by any means a complete, organized answer. Could you edit to add what the meaning of each of the four things the asker is looking to define? – 10 Replies Jan 11 '17 at 22:40
• I haven't examined the source code but from using Blender, it seems that Passive disables some calculations and probably results in lower CPU usage but reduces accuracy of the simulation. Using Active without Dynamic seems to result in more accurate simulations. – Mikko Rantalainen Oct 20 '20 at 12:32