Bug in pendulum

[vk4]

Here there are no choc (it's an axis) so where the energy goes ?

[electronicboy]

However, you also somewhat have a simulated gravity induced by the magnet, take a pendulum swinging, it will slowly lose energy as it's fighting against gravity, as well as forces/friction exerted onto the axle (they may be miniscule, but they are still there). (in fact, looking with the view forces tool and the show value's check box, it does look there is quite a bit of friction on the axle).

you also have to remember, that algodoo can only ever be so accurate, Algodoo uses a lot of high precision floating point calculations which produce the results in the application, however desktop CPUs aren't amazing at high precision FP calcs, so there is always going to be some minor calculation errors along the way, algodoo does take some steps to reduce the errors, however they can only take that so far before the error prevention limits the physics engine too much.

[vk4]

ok, but why this scene, the rotation increase alone ?

[electronicboy]

Setting legacymode to 0 on the objects axel appears to severely limit the issue, seems like the axle isn't in perfect centre, which is really a calculation issue when trying to find the dead centre of the object (with perfect precision for the calculations anyways).

However, it seams to be magnified with the new axle physics which attempt to reduce an issue in older versions of axle physics where axles would easily stretch and deform causing a magnitude of issues, which the new system fixed however did bring a few drawbacks.

[vk4]

in this scene, no axis, and the system is unstable !

idem with ellipse on a circle, maybe the force from wall works finally ! compare with a circle on a circle: no energy in addition

[vk4]

I can built a scene with no shock only rotation, the energy of the system is not fixed.

In fact, even an ellipse on Earth give more and more energy (no friction and restitution = 1, loot at xct scene, it seems it's when the ellipse change its angular velocity (change positive direction to negative or - to +)

[jon_joy_1999]

This is not a bug, this is garbage in, garbage out. If you want Algodoo to produce realistic results you have to provide it with realistic parameters. These include frictional forces, rebound forces, and any other kind of forces.
Algodoo will allow you to play God and divide by zero, but don't be surprised when it gives you nasal demons.

[vk4]

Happy new year jon_joy1999 ! I put small friction and restitution not at 1 and this give more energy too ! friction is at 0.00001 and restitution at 0.9999. And if you try with a circle all is fine with friction at 0 and restitution at 1. And even you put the frequency at 24000 Hz, it's the same result.

I try to test with friction at 0.01 and restition at 0.99 (for 2 objects) and the energy move down but sometimes (where there is rotation before schock) the energy move up. test the scene "friction1 energy inc" at time 1.4s the energy move up even friction and restitution.