Camera view: Programmatic info of plane being viewed

[TwinFan]

Current Situation / Problem Camera plugins might be interested to know which plane is the current target for an External Camera View in LiveTraffic, e.g. to take over that view.

Suggested Solution

• [x] DataRef that publishes the key (usually the hex transponder code) of the plane being viewed
• [x] Option to use external camera plugin only, ie. LT's internal view wouldn't activate, idea is to avoid flicker before external plugin springs on
• [x] Enhancement to LTAPI to have a flag in the plane being viewed plus a global function, which returns that plane

Benefits User can select camera view from within LiveTraffic, e.g. from the Aircraft List, but more powerful external camera plugins provide the actual viewing experience.

Additional context Forum post.

[TwinFan]

Camera Notification Support for 3rd party plugins now works as follows:

• LiveTraffic operates two integer shared dataRefs with global names, ie. not LiveTraffic-specific. In fact, they pick up the naming scheme as used by the shared dataRefs for textual aircraft information. Shared dataRefs have the advantage that a reading plugin can register a notification callback and several plugins can write to them and this way inform both the camera plugin as well as LiveTraffic. See SDK documentation on XPLMShareData.
  • sim/multiplayer/camera/tcas_idx is set to the TCAS index (1..63) of the aircraft being viewed, or to -1 if that aircraft has no TCAS index, or to 0 if camera view is turned off.
  • sim/multiplayer/camera/modeS_id is set to the aircraft key, usually the 24bit ICAO transponder code (like 0xAB1234=11211316) of the aircraft being viewed, or to 0 if camera view is turned off.
• A camera plugin
  • should register a notification on sim/multiplayer/camera/tcas_idx because this dataRef is set last. By the time your notification callback triggers both modeS_id and tcas_idx will be updated.
  • should, in the notification callback, read one or both values and do your camera magic if values are not 0.
  • can - optionally but welcome - write the dataRef values, too, ie. if your user switches off the camera view then update modeS_id and tcas_idx (in this order) to 0 to indicate that no camera view is on an aircraft; or even update them with aircraft info if your user selects another aircraft inside your plugin. (Note that your callbacks get called even if you set the values...weird twist of the SDK implementation.)
• Alternatively, a camera plugin can just use LTAPI, which handles all that internally:
  • Override LTAPIAircraft::toggleCamera(), which is called whenever the shared dataRef values change on the current aircraft and even provides you with a pointer to the previous aircraft if any. The LTAPIExample plugin includes an example implementation.
  • LTAPIAircraft::setCameraAc() and LTAPIConnect::clearCameraInfo() are available for write operations.

[slgoldberg]

Hi, @TwinFan, just a follow-up to say I'm finally able to spend a little time working on the integration of A-Better-Camera with these new datarefs, to implement the camera hand-off feature as requested -- thank you again for adding this!

I must say, at first blush, this design looks right -- and it's hopefully something the Laminar team can adopt and support as well, assuming that was your intent.

Can you confirm whether you've already opened a feature request with Laminar to add native support for these datarefs in an upcoming camera sprint Ben told me they may be working on a few months back? I was otherwise planning to request almost exactly this design -- but at a minimum, I can just point them to this, if that's okay with you.

I.e., was that your intention in putting these datarefs in sim/multiplayer?

(I would obviously include in the scope of changes I'd recommend to Laminar, the new cslModel and model dataref strings you defined for XPMP2 Remote Client as well, which I see you also thoughtfully placed into sim/multiplayer as well, since the combination are most if not all of what I consider missing features from last year's TCAS-override redesign in X-Plane 11.50.)

Either way, I'll post an update here when I've gotten the integration working or if I find any bugs/issues, if that's okay. (Expect such hopefully within the next day or two of this posting; though I'm not sure when I'll have my next release ready because I have a lot of other changes I want to get in for my next release.)

Thanks again.

Steve

[TwinFan]

It was FSTramp who suggested usage of shared dataRefs under sim/multiplayer (more info see the provided link and FSTramp's plugin) with the intend of more widespread use and ultimately adoption by Laminar. I don't know if he ever approached Laminar for follow-up or if even any other plugin followed the approach. I don't intend approaching Laminar on this.