Wave Sim

This package contains plugins that support the simulation of waves and surface vessels in Gazebo.

The main branch targets Gazebo Garden and no longer has a dependency on ROS.

There are new features including FFT wave generation methods, ocean tiling, and support for the Ogre2 render engine. There are some changes in the way that the wave parameters need to be set, but as far possible we have attempted to retain compatibility with the earlier versions. Further details are described below where you can also find a section describing support for legacy versions of Gazebo.

Dependencies

• A working installation of Gazebo Garden or later including development symbols.

• The simulation uses the CGAL library for mesh manipulation and FFTW to compute Fourier transforms. Both libraries are licensed GPL-3.0.

Ubuntu

• Ubuntu 22.04 (Jammy)
• Gazebo Sim, version 7.1.0 (Garden)

Install CGAL and FFTW:

sudo apt-get update
sudo apt-get install libcgal-dev libfftw3-dev

macOS

• macOS 12.6 (Monterey)
• Gazebo Sim, version 7.1.0 (Garden)

Install CGAL and FFTW:

brew update
brew install cgal fftw

Installation

Create a workspace

mkdir -p gz_ws/src

Clone and build the package

Clone the asv_wave_sim repository:

cd ~/gz_ws/src
git clone https://github.com/srmainwaring/asv_wave_sim.git

Compile the package:

Ubuntu

colcon build --symlink-install --merge-install --cmake-args \
-DCMAKE_BUILD_TYPE=RelWithDebInfo \
-DBUILD_TESTING=ON \
-DCMAKE_CXX_STANDARD=17

Source the workspace:

source ./install/setup.bash

macOS

colcon build --symlink-install --merge-install --cmake-args \
-DCMAKE_BUILD_TYPE=RelWithDebInfo \
-DBUILD_TESTING=ON \
-DCMAKE_CXX_STANDARD=17 \
-DCMAKE_MACOSX_RPATH=FALSE \
-DCMAKE_INSTALL_NAME_DIR=$(pwd)/install/lib

Source the workspace:

source ./install/setup.zsh

Build the GUI plugin (optional)

There is an optional GUI plugin that controls the wave parameters.

cd ~/gz_ws/src/asv_wave_sim/gz-waves/src/gui/plugins/waves_control 
mkdir build && cd build
cmake .. && make

Usage

Set environment variables

# for future use - to support multiple Gazebo versions
export GZ_VERSION=garden

# not usually required as should default to localhost address
export GZ_IP=127.0.0.1

# ensure the model and world files are found
export GZ_SIM_RESOURCE_PATH=\
$GZ_SIM_RESOURCE_PATH:\
$HOME/gz_ws/src/asv_wave_sim/gz-waves-models/models:\
$HOME/gz_ws/src/asv_wave_sim/gz-waves-models/world_models:\
$HOME/gz_ws/src/asv_wave_sim/gz-waves-models/worlds

# ensure the system plugins are found
export GZ_SIM_SYSTEM_PLUGIN_PATH=\
$GZ_SIM_SYSTEM_PLUGIN_PATH:\
$HOME/gz_ws/install/lib

# ensure the gui plugin is found
export GZ_GUI_PLUGIN_PATH=\
$GZ_GUI_PLUGIN_PATH:\
$HOME/gz_ws/src/asv_wave_sim/gz-waves/src/gui/plugins/waves_control/build

Ubuntu VM

If running on an Ubuntu virtual machine you may need to use software rendering if the hypervisor does not support hardware acceleration for OpenGL 4.2+. Install mesa-utils to enable llvmpipe:

sudo apt-get install mesa-utils

To use the llvmpipe software renderer, prefix Gazebo commands with the LIBGL_ALWAYS_SOFTWARE environment variable:

LIBGL_ALWAYS_SOFTWARE=1 gz sim waves.sdf

Examples

On macOS the client and server must be launched separately. The commands may be combined on Ubuntu.

Launch a Gazebo session.

Server:

gz sim -v4 -s -r waves.sdf

Client:

gz sim -v4 -g

The session should include a wave field and some floating objects.

Changes

There are some changes to the plugin SDF schema for hydrodynamics and waves.

Waves model and visual plugins

• The filename and name attributes for the wave model and visal plugins have changed.
• The <size> element has been renamed to <tile_size> and moved into <waves>
• The <cell_count> element has been moved into <waves>
• Add new element <algorithm> to specify the wave generation algorithm. Valid options are: sinusoid, trochoid and fft.
• Add new element <wind_velocity> for use with the fft algorithm.
• Add new element <wind_speed> for use with the fft algorithm.
• Add new element <wind_angle_deg> for use with the fft algorithm.

<plugin
    filename="gz-waves1-waves-model-system"
    name="gz::sim::systems::WavesModel">
    <static>0</static>
    <update_rate>30</update_rate>
    <wave>
      <!-- Grid dimensions
        - The tile_size and cell_count may be a single value
          for square grids, or a 2d vector if different resolution
          is desired along the x and y axis.
        - The cell_count must be a power of 2 for fft waves
      -->
      <!-- Either: single value for square grids -->
      <tile_size>256.0</tile_size>
      <cell_count>128</cell_count>

      <!-- Or: 2d vectors for different resolution in each axis -->
      <tile_size>256.0 64.0</tile_size>
      <cell_count>128 32</cell_count>

      <!-- Wave algorithms
        - These elements specify the wave generation method
          and wave spectrum parameters.
      -->

      <!-- Either: `fft` waves parameters -->
      <algorithm>fft</algorithm>
      <wind_speed>5.0</wind_speed>
      <wind_angle_deg>135</wind_angle_deg>
      <steepness>2</steepness>

      <!-- Or: `trochoid` waves parameters -->
      <algorithm>trochoid</algorithm>
      <number>3</number>
      <scale>1.5</scale>
      <angle>0.4</angle>
      <amplitude>0.4</amplitude>
      <period>8.0</period>
      <phase>0.0</phase>
      <steepness>1.0</steepness>
      <direction>1 0</direction>
    </wave>
</plugin>

The waves visual plugin has the same algorithm elements as the model plugin and extra elements to control the shading algorithm. Two approaches are available:

• DYNAMIC_GEOMETRY uses PBS shaders and is suitable for small areas.
• DYNAMIC_TEXTURE uses a custom shader and is suitable for tiled areas.

<plugin
    filename="gz-waves1-waves-visual-system"
    name="gz::sim::systems::WavesVisual">
  <static>0</static>

  <!-- set the mesh deformation method  -->
  <mesh_deformation_method>DYNAMIC_GEOMETRY</mesh_deformation_method>

  <!-- number of additional tiles along each axis -->
  <tiles_x>-1 1</tiles_x>
  <tiles_y>-1 1</tiles_y>
  <wave>
    <!-- `fft` wave parameters -->
    <algorithm>fft</algorithm>
    <tile_size>256.0</tile_size>
    <cell_count>128</cell_count>
    <wind_speed>5.0</wind_speed>
    <wind_angle_deg>135</wind_angle_deg>
    <steepness>2</steepness>
  </wave>

  <!--
    Shader parameters only apply when using DYNAMIC_TEXTURE
  -->

  <!-- shader program -->
  <shader language="glsl">
    <vertex>materials/waves_vs.glsl</vertex>
    <fragment>materials/waves_fs.glsl</fragment>
  </shader>
  <shader language="metal">
    <vertex>materials/waves_vs.metal</vertex>
    <fragment>materials/waves_fs.metal</fragment>
  </shader>

  <!-- vertex shader params -->
  <param>
    <shader>vertex</shader>
    <name>world_matrix</name>
  </param>
  <param>
    <shader>vertex</shader>
    <name>worldviewproj_matrix</name>
  </param>
  <param>
    <shader>vertex</shader>
    <name>camera_position</name>
  </param>
  <param>
    <shader>vertex</shader>
    <name>rescale</name>
    <value>0.5</value>
    <type>float</type>
  </param>
  <param>
    <shader>vertex</shader>
    <name>bumpScale</name>
    <value>64 64</value>
    <type>float_array</type>
  </param>
  <param>
    <shader>vertex</shader>
    <name>bumpSpeed</name>
    <value>0.01 0.01</value>
    <type>float_array</type>
  </param>
  <param>
    <shader>vertex</shader>
    <name>t</name>
    <value>TIME</value>
  </param>

  <!-- pixel shader params -->
  <param>
    <shader>fragment</shader>
    <name>deepColor</name>
    <value>0.0 0.05 0.2 1.0</value>
    <type>float_array</type>
  </param>
  <param>
    <shader>fragment</shader>
    <name>shallowColor</name>
    <value>0.0 0.1 0.3 1.0</value>
    <type>float_array</type>
  </param>
  <param>
    <shader>fragment</shader>
    <name>fresnelPower</name>
    <value>5.0</value>
    <type>float</type>
  </param>
  <param>
    <shader>fragment</shader>
    <name>hdrMultiplier</name>
    <value>0.4</value>
    <type>float</type>
  </param>
  <param>
    <shader>fragment</shader>
    <name>bumpMap</name>
    <value>materials/wave_normals.dds</value>
    <type>texture</type>
    <arg>0</arg>
  </param>
  <param>
    <shader>fragment</shader>
    <name>cubeMap</name>
    <value>materials/skybox_lowres.dds</value>
    <type>texture_cube</type>
    <arg>1</arg>
  </param>

</plugin>

Hydrodynamics plugin

• The filename and name attributes for the hydrodynamics plugin have changed.
• The hydrodynamics parameters are now scoped in an additional <hydrodynamics> element.
• The buoyancy and hydrodynamics forces can be applied to specific entities in a model using the <enable> element. The parameter should be a fully scoped model entity (model, link or collision name).
• The <wave_model> element is not used.

<plugin
  filename="gz-waves1-hydrodynamics-system"
  name="gz::sim::systems::Hydrodynamics">

  <!-- Apply hydrodynamics to the entire model (default) -->
  <enable>model_name</enable>

  <!-- Or apply hydrodynamics to named links -->
  <enable>model_name::link1</enable>
  <enable>model_name::link2</enable>

  <!-- Or apply hydrodynamics to named collisions -->
  <enable>model_name::link1::collision1</enable>
  <enable>model_name::link1::collision2</enable>

  <!-- Hydrodynamics -->
  <hydrodynamics>
    <damping_on>1</damping_on>
    <viscous_drag_on>1</viscous_drag_on>
    <pressure_drag_on>1</pressure_drag_on>

    <!-- Linear and Angular Damping -->  
    <cDampL1>1.0E-6</cDampL1>
    <cDampL2>1.0E-6</cDampL2>
    <cDampR1>1.0E-6</cDampR1>
    <cDampR2>1.0E-6</cDampR2>

    <!-- 'Pressure' Drag -->
    <cPDrag1>1.0E+2</cPDrag1>
    <cPDrag2>1.0E+2</cPDrag2>
    <fPDrag>0.4</fPDrag>
    <cSDrag1>1.0E+2</cSDrag1>
    <cSDrag2>1.0E+2</cSDrag2>
    <fSDrag>0.4</fSDrag>
    <vRDrag>1.0</vRDrag>
  </hydrodynamics>

  <!-- Control visibility of markers -->
  <markers>
    <update_rate>10</update_rate>
    <water_patch>1</water_patch>
    <waterline>1</waterline>
    <underwater_surface>1</underwater_surface>
  </markers>
</plugin>

Tests

# build with tests
$ colcon build --merge-install --cmake-args -DCMAKE_BUILD_TYPE=RelWithDebInfo -DCMAKE_MACOSX_RPATH=FALSE -DCMAKE_INSTALL_NAME_DIR=$(pwd)/install/lib -DBUILD_TESTING=ON --packages-select gz-waves1

# run tests
colcon test --merge-install 

# check results
colcon test-result --all --verbose 

Testing within a project build directory

$ cd ~/gz_ws/src/asv_wave_sim/gz-waves
$ mkdir build && cd build
$ cmake .. -DCMAKE_BUILD_TYPE=RelWithDebInfo -DBUILD_TESTING=ON
$ make && make test

Plots

Plots may be generated for some of the wave spectra and wave simulation methods:

./install/bin/PLOT_WaveSpectrum

Legacy versions

There is no plan to back-port new features to Gazebo9 or Gazebo11. The following branches are maintained for legacy support:

• gazebo9 - for Gazebo9 / ROS Melodic / Ubuntu 18.04 (Bionic).

• gazebo11 - for Gazebo11 / ROS Noetic / Ubuntu 20.04 (Focal).

In addition there are three branches that contain development iterations of the FFT wave simulation - for Gazebo11 / ROS Noetic / Ubuntu 20.04 (Focal):

• feature/fft-waves-v1
• feature/fft-waves-v2
• feature/fft-waves-v3

License

This is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This software is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

This project makes use of other open source software, for full details see the file LICENSE_THIRDPARTY.

Acknowledgments

• Jacques Kerner's two part blog describing boat physics for games: Water interaction model for boats in video games and Water interaction model for boats in video games: Part 2.
• The CGAL libraries are used for the wave field and model meshes.
• The UUV Simulator package for the orginal vertex shaders used in the wave field visuals.
• The VMRC package for textures and meshes used in the wave field visuals.
• Jerry Tessendorf's paper on Simulating Ocean Water
• Curtis Mobley's web book Ocean Optics in particular the section on Modeling Sea Surfaces and example IDL code