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I have a "Standard Walk" motion capture file from Mixamo.com. I want the character to walk into a cell fractured wall and activate the rigid body wall when it collides. However, my character does not interact with the wall when "Deactivation and Start Deactivated" is used. Character is set to Passive, Mesh, and deforming. If I try to use "Animated" for the character rigid body, the wall will explode. Very odd and unexpected. Anyone know if I'm doing something wrong? Thanks. File can be downloaded here -

https://drive.google.com/file/d/1BTsUNHyZcQn0cP98LJxaLcVUqB-bwfzt/view?usp=sharing

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  • $\begingroup$ Hello and welcome. While files, images, and external videos or links may be helpful additions they should not be the only way to obtain information about your issue. Don't make understanding your question rely on downloading a file, watching a video or visiting an external site. Use the builtin tools to upload images or gifs, along with thoroughly explaining the problem in written form so it can be indexed and searched for thus helping future visitors with similar issues. $\endgroup$ Jan 19 at 9:28

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Disclaimer: this is not a real answer, these are some explanations to why things are happening and maybe someone can find a real answer to this if possible. And although I give a method to get it working, this is definitively not the optimal solution.

Well, at first: you have to enable Animated if you want an animated Passive rigid body to interact with an Active rigid body. If it is disabled, the Active object will only interact with the static Passive object.

The reason everything explodes when you switch to Animated is that the Scale_ on the armature is at 0.01 - if you scale it by a factor of 100 so that the scale is back to 1 you will see that the character is standing directly in the wall, therefore it explodes.

Applying the scale on the armature is not a good idea because then the animation breaks. I'm actually no expert on armatures and how you can apply the scale without losing the motion. So it will not work as expected as long as the scale is off - sorry, maybe someone else can also help with this part.

However, I scaled everything by 100 to make the character's and armature's scale 1 again and then applied the scale on the other objects. Now the wall did not explode anymore.

But then nothing happens. The wall does not react to the character, even if Animated is enabled. The problem is explained usually that rigid bodies do not interact with posed meshes, only the base meshes. If you animate the armature object going through the wall, it would react. When the armature object stays in place and only the bones are moving the character through the wall by posing them, the wall keeps standing.

And now the thing is - and I don't know if it's a feature or a bug, because it seems to work inconsistently - I parented the floor to the character mesh (both have their origins in the same location) and all of a sudden the wall reacts to the character. The character is set to Passive, Animated and the Collisions to Mesh > Deform > Deforming. The rigid body settings on the floor cannot be changed now, there is an error message saying "Rigid Body can't be child of a non compound Rigid Body". Same thing vice versa if I parent the character to the floor.

The problem with this is first of all the simulation does not look realistic, the wall pieces are still flying away from the character like in slow motion after contact. Probably everything is on such a large scale now.

Then the other thing is, most of the time it works, sometimes it doesn't. And in a simple test I made with two cubes, one parented to a bone, and a plane as floor, I needed the floor parenting to make the active cube react to the passive cube, but then it worked still after I unparented them again. Also most of the time Deform works, but sometimes Final as well. Then while playing around, the scene with only two cubes,a bone and a plane crashed for no apparent reason.

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  • $\begingroup$ Thank you for taking a look at this. I find that if I leave animated off on the character just have deforming mesh, it will interact correction with the cell fractured wall, as long as the wall components are not using "Deactivation" and "Start Deactivated" My guess is that it is a bug since the behaviour is not consistant and unexpected. I do agree about the scale of the armature. I'm not sure how to correct that from Mixamo. I'll check to see if Mixamo has a scale option. $\endgroup$ Jan 19 at 18:34

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