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I find problems in the Blender physics engine even in simulating simple fall of a sphere. I probably have done some setup wrong because i've also tried bullet engine stand-alone and it works better.

This is the experiment setup:

  • 24 fps

  • sphere positioned in (0,0,0) with mass 1 kg

  • gravity set to (0,0,-10 m/s^2)

  • no friction, no bounciness, no damping

  • steps per seconds and solver iteration set to 1000

At frame 72 ( 3 seconds ) using the formula costant accelerated motion formula the sphere should be at -45m but instead it is at -43,76m! I measured the position snapping cursor to object at selected times.

I thought that there were a constant friction somewhere but i calulated the second derivative to get the acceleration and it's not constant at -10 m/s^2!

Solved

i've had to put my animation start from frame 0 instead of 1. Also in Rigid body cache in Scene setting.

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    $\begingroup$ Just checking... your first frame is 0? $\endgroup$ – Robin Betts Feb 16 at 23:54
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    $\begingroup$ Yes, that was the problem! I've got -44,98m now. That's enough considered the numerical error made by calculations. Thank you for the hint. $\endgroup$ – federicoB Feb 17 at 13:50

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