ALS technical notes: Difference between revisions

The ALS framework supports a generic implementation of landing lights and a searchlight which are based on a framerate friendly computation in screen coordinates, i.e. the lights project correctly '''''only if the light is close to the viewer''''' (typically, that'd be from cockpit view). In other words, this is not a full (rather expensive) computation of light volumes as Rembrandt does it but a much faster test of illuminated screen areas.

[[File:Landing light03.jpg|400px|Cessna 172 p using generic ALS landing lights]]

Two landing lights and a searchlight are supported. The landing lights have a fixed position with respect to the aircraft axis (technically, with respect to the default view axis as defined in the respective view), whereas the searchlight follows any offset of the view axis in view mode, i.e. when using the mouse to look around, the searchlight will follow the motion, the landing lights will not. The lights require ALS to run above basic quality level and work on runway and airport keep above transition setting 3 and everywhere else only at highest quality setting. All lights are controlled via properties in '''/sim/rendering/als-secondary-lights/'''.

The names of the properties should be self-explanatory, if for instance if '''use-searchlight=true''' then the searchlight (which always follows the current view axis) is used.

 

The properties '''landing-light1-offset-deg''' and '''landing-light2-offset-deg''' allow to specify angular offsets for the landing light which are then not centered on the view axis. This can be used to simulate one or two landing lights set in the wings.

A third offset '''landing-light3-offset-deg''' is available which allows for a vertical offset.

Especially useful for tail dagger aircraft.

The lights can be switched on and off from the property browser for any aircraft without any modifications to the aircraft definition. Implementing them correctly aircraft side thus just involves linking the landing light switches to the ALS control properties and setting the correct angular offsets. Additionally, it is recommended to switch the lights off unless in a cockpit view, as they don't project correctly for any external view.