VRML Audio Tutorial

The Nodes

The Sound Node

Here is the syntax of the Sound Node:

Sound {
  exposedField     SFVec3f     direction     0 0 1
  exposedField     SFFloat     intensity     1
  exposedField     SFVec3f     location      0 0 0
  exposedField     SFFloat     maxBack       1
  exposedField     SFFloat     maxFront      1
  exposedField     SFFloat     minBack       1
  exposedField     SFFloat     minFront      1
  exposedField     SFFloat     priority      0
  exposedField     SFNode      source        NULL
  field            SFBool      spatialize    TRUE
}

Understanding the Sound Model

Use the viewpoints in the file above to navigate to the different parts of the model.

In its most simple model, sound in VRML looks like two ellipsoids, one nested inside the other, with the inner ellipsoid located at one foci of the outer ellipsoid (ellipses have two focal points). The sound file emanates from the inner ellipsoid, and goes out in one direction toward the other foci of the outer ellipse. The sound source radiates out as the shape of the ellipsoids. It mimics the real world by having a volume drop off at 1/r squared, which occurs for sound travelling with no resistance or, as they say, in an anechoic chamber. Therefore, when you enter the outer ellipsoid, you hear the sound very quietly, and as you approach the inner ellipsoid, the volume increases. Once you enter the inner ellipsoid, the sound becomes ambient, which is to say the volume remains constant. No sound is heard outside the outer ellipse.

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