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X-Plane: Compatibility of sloped runways with other clients?

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In X-Plane we were used to disable sloped runways (Settings/General: "Runways follow terrain contours") to fly online. Since swift appears to reliably adjust other planes to ground level in X-Plane 11, I am wondering what the effects of keeping sloped runways enabled would be when using swift?


There are a few cases to be considered: (transmitting coordinates from => to, local client in bold; I'll ignore XSB with sloped runways enabled as that's an unusual setup)


  1. XP swift, sloped => XP swift, not sloped
  2. XP swift, sloped => other sim (e.g. FSX/P3D) with swift, not sloped
  3. XP swift, sloped => any sim, other client, not sloped
  4. any sim, any client, not sloped => XP swift, sloped


I would [Mod - Happy Thoughts]ume that cases 1 and 4 should look fine as swift corrects the height to ground level in XP (at least before takeoff and after landing)?


My guess is that swift might be able to correct the height of ground-level planes in other sims (FSX/P3D) as well, so case 2 may be OK as well.


The really interesting case is number 3; how would a swift X-Plane user on a sloped runway look to someone using vPilot or FSInn on FSX/P3D where sloped runways simply don't exist at all (except for very rare scenery addons)? I don't remember other clients being successful (or even attempting?) to correct other clients to ground level, so would that simply be another case of airplanes sinking into the ground/hovering in the air (same as it has always been) or does swift "normalize" heights before sending local coordinates to the network, so it would make swift users on ground compatible to other, less capable clients?

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As the vPilot developer, I can give some insight into how case 3 will behave with vPilot.


vPilot has a ground clamping feature where it will adjust the height of the aircraft to match your local terrain. So you will normally not see other users floating above ground, or sinking below ground. This works regardless of which simulator or pilot client the other pilot is using.


There is, however, one specific case where you could still end up seeing another user floating above ground. This is something I discovered recently and will be releasing a fix for in the near future.


The case is when the other pilot is using X-Plane with sloped runways enabled, and when they land, the runway elevation in their sim is below the runway elevation in the vPilot user's local sim. At the moment that the X-Plane user touches down, vPilot calculates a terrain offset. In this case, that terrain offset would be a positive number, for example 20 feet. That means that the local terain is 20 feet higher than the X-Plane terrain in the other pilot's sim. Then, if the user taxis along on the ground, and the sloped runway rises up to a higher elevation, then the vPilot user will see the X-Plane user's aircraft floating above ground, because vPilot will be continually applying that 20 foot offset to whatever altitude the X-Plane user's client is reporting. So if their altitude is rising due to a sloped runway, then their aircraft will rise in the vPilot user's view accordingly.


I will be releasing a fix for this at some point soon, which will cause vPilot to keep the aircraft glued to the ground as long as the other aircraft is still reporting itself as being on the ground. This will only work for new clients that support sending the "I'm on the ground" flag across the network, which swift does, as far as I know.


As for other clients (Squawkbox, FSInn) with case 3, I don't really know what'll happen, but I [Mod - Happy Thoughts]ume you'll get floating aircraft.

Developer: vPilot, VRC, vSTARS, vERAM, VAT-Spy

Senior Controller, Boston Virtual ARTCC

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  • 4 weeks later...

This is a good question. Yes, when the receiving client is either swift or vPilot, it should work fine, regardless of what the other client is.


But if swift is sending, and the receiving client is neither swift nor vPilot (e.g. it is XSB with contoured runways turned off) then the receiving client might see you floating or tunnelling above or below ground. But that has always been the problem with the legacy clients and scenery differences, swift can't solve that. It could be mitigated by disabling contoured runways on your X-Plane when using swift, but the legacy client users will still see some other aircraft floating or tunnelling due to scenery differences regardless of whether their contoured runways are turned on or off.

swift - Developer
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