Creating HUDs
Heads up display (abbreviated HUD)
Most scripted functionality works with HUDs
Particles do not. Don't have HUD prims generate them. If a HUD attempts to generate particles, they appear at <0,0,0> in the current sim, annoying your neighbors.
If a sound is triggered using llPlaySound(), only the HUD wearer will hear it. If the land parcel they're over restricts sound entry/exit, the sound will not play.
If a sound is triggered using llTriggerSound(), the wearer and any bystanders will hear it.
Scripted movement of HUD pieces is relative to the attachment points. The position vector used by llSetPos() is interpreted as . A depth of -1 will render in front of a depth of 0.
Since HUD attachments cannot be clicked thru even if they're invisible, the common solutions to getting them out of the way are moving them and shrinking them.