UWSim trunk has been updated with some updates that are worthy to be briefly described. TF publisher offers a simple interface to publish via ROS TF the frames of every object, vehicle, vehicle part and sensor present in the scene in a tree structure with virtual world root. Objects publishing is optional and rootName can be configured, vehicle's parts use a prefix with the vehicle's name to avoid collision on tf identifiers. To add it the following lines should be added in the rosinterfaces block of the XML config file.

  <WorldToROSTF>
    <rootName> world </rootName>
    <enableObjects> 1 </enableObjects>
    <rate>10</rate>
  </WorldToROSTF>

Trajectory trails have been completely re-implemented so they can represent object movements and vehicle parts movements. Additionally trajectory trails can be hidden / displayed pressing “t” key. Instead of adding a config line inside vehicle XML block, trajectory trails are configured using showTrajectory blocks inside simParams as the following example shows:

  <showTrajectory>
    <target>girona500</target>
    <color>
      <r>1.0</r>
      <g>0.0</g>
      <b>0.0</b>
    </color>
    <lineStyle> 1 </lineStyle>
    <timeWindow> 30 </timeWindow>
  </showTrajectory>

Only target field is required to add a trajectory trail configuring the object that will draw a trajectory while moving. The other tags allows us to decide color lineStyle, where 1 is continuous line 2,3,4 are different kinds of dashed lines and timeWindow, which is an option to limit the trail to the last X seconds.

Finally, last (but not least!) update is the change of the bullet physics solver to Dantzig and bullet 2.82. This changes lead to better contact physics as shown in our tests heading to a better manipulation simulation.

The UWSim structured light projector displays user configured textures over the scene along the -Z axis (osgcamera like) of their local frame . This projector is able to simulate arbitrary laser and vehicle lights casting realistic shadows. Here we can see an example of use:

  <structuredLightProjector>
    <name>laser_projector</name>
    <relativeTo>sls</relativeTo>
    <fov>21</fov>
    <image_name>data/textures/laser_lines.png</image_name>
    <laser>1</laser>
    <position>
      <x>1</x>
      <y>0</y>
      <z>0</z>
    </position>
    <orientation>
      <r>0</r>
      <p>3.14</p>
      <y>1.57</y>
    </orientation>
  </structuredLightProjector>

As usual the previous XML code adds a structured light projector at the given position and orientation with respect to sls. fov tag configures the field of view of the projector (also known as angle of view). image_name tag provides the image to project, RGBA images are allowed but alpha channel will be used as a binary value to project or not project the texture on every pixel. Finally laser label decides if the projection should be treated as laser or not, main difference is laser light does not suffer attenuation along distance and it does not mix with objects color.

After a long time without news and updates about UWSim we are going to retake it. In this first message we will try to sum up the most important changes and additions to the simulator since the last post. We will extend these features in the next messages.

UWSim is already available for the hydro and indigo ROS distributions. Although main branch is still hydro fixes and updates are periodically moved from hydro to indigo. Both branches are compatible with OSG 3.2. 

Three new sensors are available for simulated vehicles, to know:

• Multibeam sensor: More info here.

• Structured light projector: More info here.

• Force sensor: More info here.

Finally some small features have been updated such as TF publishing, trajectory trails and bullet physics version and solver for more information visit extended news.

During his PhD. research stay, Juan Carlos García has presented the TRITON research project to the members of the "Instituto de Sistemas e Robótica", from Universidade de Coimbra.