Homeworld Effects Manual: setPseudoBillboard()

setPseudoBillboard(int value)

Keeps a mesh oriented towards the camera.

If value is 1, this is active. Otherwise, this is inactive.

setPseudoBillboard() rotates a mesh around its z-axis to keep its y-axis pointed at the camera. This is used mainly for beam weapons. The beam is a flat mesh with an animated texture. The mesh is always oriented with its flat side facing the camera, so it looks like a solid beam, instead of a wimpy flat thing with a picture on the side. This illusion can be defeated by looking along the path of the beam. Sprites and circles are always pointed towards the camera, so setPseudoBillboard() is unnecessary for them. Points and lines don't have any flat sides to face towards the viewer, so this command is pretty much only for meshes.