# How to enable bounce with DART engine?

Hi all,

I want to simulate bounce with the DART engine. I set restitution_coefficient and threshold under the bounce tag, however, it does not work.

This answer says that max_vel value under the ode tag must be also set. However, max_vel is valid only when ODE is set as the physics engine.

In addition, when max_vel is set, restitution_coefficient and threshold are ignored, then kp and kd under the ode tag are referred (This answer's last comment mentions it).

Is there any way to set a restitution coefficient with DART engine?

Here is my world.sdf and I run it Gazebo 9 on Ubuntu18.04.

Thank you.

<?xml version="1.0" ?>
<sdf version="1.6">
<world name="world">
<gravity>0 0 -9.80665</gravity>
<physics default="true" type="dart">
<dart>
<solver>
<solver_type>dantzig</solver_type>
</solver>
</dart>
</physics>
<!-- <physics type="ode">
</physics> -->

<!-- A global light source -->
<include>
<uri>model://sun</uri>
</include>

<!-- Ground -->
<include>
<uri>model://ground_plane</uri>
</include>

<!-- Ball -->
<model name="Ball">
<static>false</static>
<pose>0 0 2 0 0 0</pose>
<pose>0 0 0 0 0 0</pose>
<inertial>
<pose>0 0 0 0 0 0</pose>
<mass>8</mass>
<inertia>
<ixx>3.2</ixx>
<ixy>0.0</ixy>
<ixz>0.0</ixz>
<iyy>3.2</iyy>
<iyz>0.0</iyz>
<izz>3.2</izz>
</inertia>
</inertial>
<visual name="vis_Ball">
<geometry>
<sphere>
</sphere>
</geometry>
</visual>
<collision name="coll_Ball">
<pose>0 0 0</pose>
<geometry>
<sphere>
</sphere>
</geometry>
<surface>
<bounce>
<restitution_coefficient>1</restitution_coefficient>
<threshold>0</threshold>
</bounce>
<!-- <contact>
<ode>
<kp>1e+12</kp>
<kd>1</kd>
<max_vel>1000</max_vel>
</ode>
</contact> -->
<friction>
<ode>
<mu>0</mu>
<mu2>0</mu2>
</ode>
</friction>
</surface>
</collision>