I am trying to pick a soft ball using two arms and then throw it. I am using a soft ball because I want to be able to throw the ball even when it is slightly crushed by the fingers.

But when I try to run it using gazebo, the ball jumps around on contact. I tried making the object soft using different values of kp, kd, soft_cfm and soft_erp with no success. Any suggestions on how I can achieve this.

ball.sdf

<model name="basketball">
    <static>false</static>
    <link name="ball">
      <inertial>
        <mass>0.25</mass>
        <!-- inertia based on solid sphere 2/5 mr^2 -->
        <inertia>
          <ixx>0.00169</ixx>
          <iyy>0.00169</iyy>
          <izz>0.00169</izz>
          <ixy>0</ixy>
          <ixz>0</ixz>
          <iyz>0</iyz>
        </inertia>
      </inertial>
      <visual name="visual">
        <geometry>
          <sphere>
            <!-- <radius>0.1172</radius> -->
            <radius>0.13</radius>
          </sphere>
        </geometry>
      </visual>
      <collision name="collision">
        <geometry>
          <sphere>
           <radius>0.13</radius>
          </sphere>
        </geometry>
      </collision>
    </link>
  </model> 

finger.sdf

<model name="finger">
  <joint name="asdf" type="fixed">
    <parent link="world"/>
    <child link="finger_link"/>
    <pose frame="">0 0 0 0 1.5707963267948966 0</pose>
  </joint>
  <link name="finger_link">
    <visual name='visual'>
      <pose frame="">0 0 0 1.5707963267948966 0 0</pose>
      <geometry>
        <mesh><uri>model://finger/finger.stl</uri></mesh>
      </geometry>
      <material name="white"/>
    </visual>
    <inertial>
      <pose frame="">0 0 0 0 0 0</pose>
      <mass value="0.250"/>
      <inertia ixx="0.0" ixy="0.0" ixz="0.0" iyy="0.0" iyz="0.0" izz="0.0"/>
    </inertial>
  </link>
</model>

Just before the contact between the fingers and the ball

Collision model