Real-Time Physics Simulation Forum 2006-10-05T00:00:20+00:00 https://pybullet.org/Bullet/phpBB3/app.php/feed/topic/574 2006-10-05T00:00:20+00:00 2006-10-05T00:00:20+00:00 https://pybullet.org/Bullet/phpBB3/viewtopic.php?p=2037#p2037 <![CDATA[Vertical static planes]]>
Something terrible with setLinearVelocity!

In appCcdPhysicsDemo, in localCreateRigidBody add before return:

body->setLinearVelocity(btVector3(1,6,1));

And see that crazy dance. They are jumping and jumping. They can not stop. They are gaining impulse from nothing....
It's not that terrible, more funny :-)

I added an assert so that you don't setLinearVelocity on static objects, like the ground. Bullet 1.x had support for kinematic objects (non-dynamic but with velocity). Due to removal of CcdPhysicsEnvironment, Bullet 2.x doesn't have this feature yet. It will be added soon. Then the ground will just move as well, without this funny behaviour.
Bullet 2.12 will have this check, and also other improvements. it will be released later today.

Thanks again for the feedback!
Erwin

Statistics: Posted by Erwin Coumans — Thu Oct 05, 2006 12:00 am

]]> 2006-10-03T10:22:24+00:00 2006-10-03T10:22:24+00:00 https://pybullet.org/Bullet/phpBB3/viewtopic.php?p=2029#p2029 <![CDATA[Vertical static planes]]>
In appCcdPhysicsDemo, in localCreateRigidBody add before return:

body->setLinearVelocity(btVector3(1,6,1));

And see that crazy dance. They are jumping and jumping. They can not stop. They are gaining impulse from nothing....

Statistics: Posted by Jack — Tue Oct 03, 2006 10:22 am

]]> 2006-10-02T09:17:40+00:00 2006-10-02T09:17:40+00:00 https://pybullet.org/Bullet/phpBB3/viewtopic.php?p=2019#p2019 <![CDATA[Vertical static planes]]> And discover something strange with vertical static planes.

Situation:
Room built of 5 static planes. Top, Bottom, Left, Right and Rear.
Gravity: btVector3(0, -9.8f, 0)
SPHERE inside the Room. SPHERE has some starting linear velocity. SPHERE is jumping inside the room reflecting from static planes. It reflects OK from Top and Bottom horizontal planes. But when it touches vertical wall, it does not reflect correctly. It is "glued" to vertical wall and jumps in vertical direction near the wall.

Sometimes also SPHERE becomes to gain energy from "nothing" (it jumps faster and faster). But it depends. I think it happends when Restitution=1

Statistics: Posted by Jack — Mon Oct 02, 2006 9:17 am

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