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Just for making the problem simple to understand ( in reality I want to simulate a robot ), I want to make a rigid body wheel and animate its spinning then start simulation and see how it rolls forward, but the object can only be animated or simulated I don't see an option to combine both at the same time. Is it possible to do it in blender?

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  • $\begingroup$ Shall it spin forward or backwards? $\endgroup$
    – Chris
    Commented Mar 28, 2022 at 13:27

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No. You can do either do physics or animated an object.

The only thing you can do it change this behaviour every frame (if you want to). It is the "animated" checkbox in the rigid body settings. If it is unchecked, gravity works, if it is checked, gravity and all forces are "off" and you can keyframe your animation.

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  • $\begingroup$ Well, "change this behaviour every frame" doesn't really work. Because if you disabled Animated and let the physics simulation take over, you cannot switch back to animation. I mean, you can, but it will make the object snap back to where it was before the simulation started and I'm not sure if this is the desired effect... because the simulation doesn't change location or rotation of the object. $\endgroup$ Commented Mar 28, 2022 at 9:04
  • $\begingroup$ @GordonBrinkmann: maybe i didn't make it clear enough: i didn't meant "change it every frame to solve it" but it is possible to change it every frame - as a general possibility. $\endgroup$
    – Chris
    Commented Mar 28, 2022 at 9:09
  • $\begingroup$ Of course, everything that can be keyframed can also be keyframed each frame ;) $\endgroup$ Commented Mar 28, 2022 at 9:21
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You can actually animate the state of the checkbox.

So in the beginning, when you're hand animating the wheel, keep it as "animated". When you're done, set a keyframe of the checkbox by hovering over it and hitting "I". Then go to the next frame, uncheck the box, and hover over it and hit "I" again to set another keyframe.

You may have to play with the animation to make sure the physics are doing what you want but it is possible. Usually the physics takes into account the speed of the object during the manual animation.

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  • $\begingroup$ thank you for your answer , I think Blender might not be the tool I need for this $\endgroup$ Commented Mar 28, 2022 at 12:07
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I found a solution after trying all methods of joining geometry inside a rigid body , making the object and animating it inside GEO NODES works with physics at the same time but it is not reliable nor predictable enough to simulate machinery or a robot

this is a small test I did BLENDER GEOMETRY NODES RIGID BODY

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  • $\begingroup$ You made my day. Not reliable and not predictable - but you propose this as an answer? Sorry, can’t stop laughing πŸ˜‚πŸ˜‚πŸ˜‚πŸ˜‚πŸ˜‚ but I love your humor! +1 for making me laugh $\endgroup$
    – Chris
    Commented Mar 28, 2022 at 12:07
  • $\begingroup$ hahaha I'm glad I made you laugh lol XD , but I thought it could be useful for some people (motion graphics stuff or explosions) just not for for me cause I want so simulate a machine and changing the geometry I can not simulate a rotatory friction against the ground , the problem is the wheels rotate but they don't move forward they just bounce $\endgroup$ Commented Mar 28, 2022 at 13:22
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Using Rigid body constraints seems the way to go, adding motor and slide forces to the parts of the robot, so dumb I didn't see it before ...

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