Gazebo GpuRaySensor

The Gazebo GpuRaySensor provides an array of mXn rays prepared using the gazebo::rendering::GpuLaser module. These rays are of type GpuLaserData and contain the following fields:

• beam: The vertical beam plane index, [0, vRes) (the beam row)
• intensity: The intensity value we want
• range: The distance value we want
• reading: The horizontal index, [0,hRes) (the beam column)

We need this record to additionally include:

• incident_angle based on reflection. If we model secondary reflection, then we need vertical and horizontal angles. Otherwise we can get by with one normal angle.

Because GpuLaser is in a layer below GpuRaySensor and its internals are not accessible (and because sensor::visualize does not recognize custom sensor types for rendering ray lines), we need to build Gazebo from source so we can add the incident_angle field. We would additionally make a new BeamSensor type (beam as opposed to ray or gpu_ray) that would produce one horizontal sweep of Sonar Beam data as an array. Initially, output will be n records of (intensity, range) tuples. Later, these fields will be n records of arrays of (intensity, range) tuples where a given array of (intensity, range) tuples will consist of multiple range values.

Alternatives considered were:

• dsros_dvl: No, this uses the Physics instead of graphics engine.
• Depth camera: We want rays, not rasterization. However, we notice that incident angle support is being introduced to Gazebo using the Depth camera interface, ref. https://bitbucket.org/osrf/gazebo/pull-requests/3193/added-normals-in-depth-camera-sensor.