SoVRMLVisibilitySensor(3) on Linux
The text a2e7921b73f3, as Debian 8 (Jessie) shipped it.
The SoVRMLVisibilitySensor class will generate events based on visibility. The detailed class documentation is taken verbatim from the VRML97 standard (ISO/IEC 14772-1:1997). It is copyright The Web3D Consortium, and is used by permission of the Consortium: