# Adjust max_contacts paramters for a ball

Hey, there I would like to set the physics parameter of a ball balancing on a plate in a realistic way: -> the ball should have some grip -> the ball should start rolling at a certain angle

Now this is what I currently have for the ball:

  <gazebo reference="ball_link">
<gravity>1</gravity>
<maxVel>1000</maxVel>
<minDepth>0</minDepth>
<mu1>0.5</mu1>
<mu2>0.5</mu2>
<fdir1>0 0 0</fdir1>
<kp>1e+20</kp>
<kd>1.0</kd>
<selfCollide>0</selfCollide>
<maxContacts>3</maxContacts>  <!-- set this to 1 and ball stops sliding with high angle -->
<material>Gazebo/Blue</material> <!-- caution this overrwrites (dae) everything!!! -->


</gazebo>

And for the plate:

  <gazebo reference="ee_link">
<material>Gazebo/White</material>
<selfCollide>0</selfCollide>
<maxContacts>10</maxContacts>
<mu1>0.5</mu1>
<mu2>0.5</mu2>
</gazebo>


Now the problem is, that when the plate angle is slowly increasing and the max_contacts of the ball is not 1 it occurs a behaviour like in the picture:

ball_plate.png

On the other hand if I set the max_contacts value of the ball not to 1 the ball is moving instantly already on very small angles of the plate (which I also do not want....)

How to set the maxContacts of the Ball corretly? Should I also adjust the mu1, mu2 values of the plate and ball? (They should have the same value or?)

Best and Thanks :) Markus

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