Chapter 12B, Environment Sensors and Sound: ProximitySensor, VisibilitySensor
Channel: X3D for Web Authors
Date: 2016-04-13

Chapter 12B, Environment Sensors and Sound: ProximitySensor and VisibilitySensor nodes.  Examples, slides online at http://x3dgraphics.com/examples/X3dForWebAuthors/Chapter12-EnvironmentSensorSound