README.md

Ball and Paddle in Python

This is a simple example of using the hydroelastic contact model in Python. The example drops a compliant-hydroelastic ball on a compliant-hydroelastic paddle (represented as a box). The two bodies are defined in SDFormat files.

The compliant paddle is a box of size 20x20x2 cm. It is stationary and posed in World frame such that its top surface is on and aligned with the World's X-Y plane. The center of its top surface is at World origin.

The compliant ball has radius of 2 cm. By default, it is dropped 4 cm above the paddle.

Run the visualizer

bazel run //tools:meldis -- --open-window &

Run the example

bazel run //examples/hydroelastic/python_ball_paddle:contact_sim_demo_py

Drop the ball near the paddle's edge

We specify very low target_realtime_rate so that we can see it easier.

bazel run //examples/hydroelastic/python_ball_paddle:contact_sim_demo_py -- \
--ball_initial_position 0.101 0 0.05 \
--target_realtime_rate=0.04 \
--simulation_time=0.09

Drop the ball near the paddle's corner

We specify even lower target_realtime_rate so that we can see it easier.

bazel run //examples/hydroelastic/python_ball_paddle:contact_sim_demo_py -- \
--ball_initial_position 0.102 0.102 0.05 \
--target_realtime_rate=0.02 \
--simulation_time=0.09

Other Options

There are other command-line options that you can use. Use --help to see the list. For example, you can use --contact_model=point to test point contact.

bazel run //examples/hydroelastic/python_ball_paddle:contact_sim_demo_py -- \
--help