Saturday, December 05, 2009

What Exactly Is a Generic Light?

X-Plane 940 has these generic light things...what the heck are they? Here's the story:

X-Plane has been growing a larger number of independently simulated landing lights with each patch. We started with one, then four, now we're up to sixteen. Basically each landing light is a set of datarefs that the systems code monitors.
  • You use a generic instrument to hook a panel switch up to a landing light dataref.
  • The sim takes care of matching the landing light brightness with the switch depending on the electrical system status.
  • Named lights can be used to visualize the landing lights.
See here for more info.

But what else lights up on an airplane? Sergio sent me the exterior lighting diagram for an MD-82, and it would make a Christmas tree blush. There are lights for the staircases, for the inlets, on the wings, pointing at the wings, the logo lights, the list goes on.

We have sixteen landing lights, so we could probably "borrow" a few to make inlet lights, logo lights, etc. But if we do that, the landing light will light up the runway when we turn on any of those other random lights.

Thus, generic lights were born. A generic light is a light on the plane that can be used for any purpose you want. They aren't destined for a specific function like the strobes and nav lights. There are 64 of them, so divide them up and use them how you want. Just like landing lights, you use a generic light by:
  • Using a generic instrument to control its "switch" from the panel.
  • Using a named light to visualize it somewhere on the OBJs attached to your airplane.
Generic lights don't cast any light on any other part of the plane - sorry. You can use ATTR_lit_level to light up part of your mesh dynamically when the generic light comes on though - the effect can be convincing if carefully authored.

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