Box on an inclined plane... friction?
Posted: Thu May 12, 2011 11:44 am
Hi everyone!
I'm doing some tests with several physics simulation tools and I've found something interesting when it comes to friction in Bullet.
I have a box on an plane. The plane is inclined by an angle phi. The friction parameter "mu" is set to 0.35 on both of them.
Analytically, one can show that the box should start to slide on the plane when the plane is inclined by phi=19.3 degrees. This is the case in all the other simulation tools, but not Bullet... The box starts to slide at phi=6 degrees.
The "box" is not really a box, it's a tetrahedron made out of 4 composite spheres. Why? Because I want to avoid any possible artifacts when having more than 3 contacts at the same time. Also, not all of the simulation tools support rigid body boxes.
The plane is just a static rigid body box.
I set the friction with btRigidBody->setFriction(0.35) on both bodies. I also tried to set the friction to higher values and that seem to make the "box" stay on the plane. This indicates the friction is there at least.
How can I make this test physically correct with Bullet? Or is this even possible?
Stefan
I'm doing some tests with several physics simulation tools and I've found something interesting when it comes to friction in Bullet.
I have a box on an plane. The plane is inclined by an angle phi. The friction parameter "mu" is set to 0.35 on both of them.
Analytically, one can show that the box should start to slide on the plane when the plane is inclined by phi=19.3 degrees. This is the case in all the other simulation tools, but not Bullet... The box starts to slide at phi=6 degrees.
The "box" is not really a box, it's a tetrahedron made out of 4 composite spheres. Why? Because I want to avoid any possible artifacts when having more than 3 contacts at the same time. Also, not all of the simulation tools support rigid body boxes.
The plane is just a static rigid body box.
I set the friction with btRigidBody->setFriction(0.35) on both bodies. I also tried to set the friction to higher values and that seem to make the "box" stay on the plane. This indicates the friction is there at least.
How can I make this test physically correct with Bullet? Or is this even possible?
Stefan