See the Python reference of this logic brick in
The Ray Sensor shoots a ray in the direction of an axis and sends a positive pulse once it hits something. It can be filtered to only detect objects with a given material or property.
See Sensor Common Options for common options.
This field can be used to limit the sensor to look for only those objects with this property.
Unless the Property field is set, the Ray sensor can detect objects “through” other objects (walls, etc.).
Objects must have Physics “Actor” property enabled to be detected.
This menu determines the direction of the ray. The ± signs is whether it is on the axis direction (+), or the opposite (-).
Determines the length of the ray (in Blender units).
- X-Ray Mode button
Makes it x-ray, so that it sees through objects that do not have the property or material specified in the filter field.