floaters and land sharks

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Keith Smith
Posts: 9939
Joined: Sat Oct 09, 2010 8:38 pm
Location: Pompton Plains, NJ
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floaters and land sharks

Post by Keith Smith »

We've all seen planes partially submerged under a taxiway with just their tails sticking out, planes floating 20-30ft in the air, or worse, failed to see aircraft at all because they're actually 30ft underground.

This is all caused by differences in terrain meshes. For example, here is the list that I know of:
-fs9
-fsx
-xplane stock terrain( sloped runways off)
-xplane stock DSF (sloped runways on)
-xplane altpilotx HD mesh (sloped runways off)
-xplane altpilotx HD mesh (sloped runways on)
- ortho4xp mesh (sloped runways off)
- ortho4xp mesh (sloped runways on)
- Glitter Gulch custom scenery for LAS...

and I'm sure there are many, many others.

At the moment, the PilotEdge plugin simply draws the planes exactly where it's told with no regard for terrain. This is changing as we speak. I've been reviewing approaches for a while and have finally had a chance to take a crack at the issue. I'm pleased with what I'm seeing so far.

To set expectations realistically, the goal is to avoid floaters and land sharks...but it's not likely to produce a perfect outcome for departing and arriving aircraft. There will some odd behavior (I'll explain it in more detail when the updated plugin is released). It will be a vast improvement over the current situation, though. A 100% solution would require a massive investment of resources, which has diminishing return. I believe that a quick surgical strike will yield a strong result, so that's what I'm working on for now.

I will lay out exactly what's going on, what the ideal solution would be, the reasons why we can't easily achieve that solution, and then explain the solution we're actually rolling out.

For now, though, back to coding I go.
gavink42
Posts: 171
Joined: Mon Apr 16, 2012 7:08 pm
Location: KMEM

Re: floaters and land sharks

Post by gavink42 »

Thanks Keith! I'm looking forward to getting back on the network soon. Your efforts are much appreciated!

- Gavin
- PP ASEL, instrument, complex, high performance
- Member AOPA, EAA, IMC Club, Piper Owner Society
- Cherokee 180C owner
rtataryn
Posts: 344
Joined: Wed Mar 04, 2015 10:19 pm
Location: Spokane, WA

Re: floaters and land sharks

Post by rtataryn »

Wonderful news Keith! Thank you for working on this!!! It will make group flights and events so much better. Looking forward to hearing more about your findings and solution.
Rod
PPL, Instrument, ASEL, ASES
2013 Cirrus SR22T N877MS
2018 Icon A5 N509BA
1946 Piper J3 Cub N7121H
1942 Stearman N2S N6848
Keith Smith
Posts: 9939
Joined: Sat Oct 09, 2010 8:38 pm
Location: Pompton Plains, NJ
Contact:

Re: floaters and land sharks

Post by Keith Smith »

Not gonna lie, this is a big step forward! The PilotEdge v1.3.1 xplane plugin is now available and supports the 'ground clamping' logic required to pretty much get rid of land sharks and floaters.

From the release notes for that plugin:
- initial release of clamping of targets (reducing floaters and land sharks). Logic is simple, if target is known to have weight on wheels, it will be drawn at ground level to the best of our ability. Without a weight on wheels indication, for aircraft < 100AGL, we clamp any non-helicopter traffic if it's doing 30kts or less over the ground. while helicopter traffic is clamped if it's doing 1kt or less.

If an aircraft would normally be drawn at what we consider to be LESS than a minimal viable altitude (based on terrain height, strut compression and known gear height), we draw it at ground level.

Between those two cases, we cover land sharks and floaters.

There are issues with this approach, namely a lack of smooth progression from clamped to non-clamped. Namely, a clamped floater will jump off the ground aggressively once it breaks ground. Conversely, land sharks linger on the runway during rotation (while their real altitude catches up to the artificially high altitude we are drawing them at to keep them above ground). This MAY be addressed in a future implementation with smoother progressions between clamped and non-clamped states.
As a reminder, for any of this to work properly, you MUST ditch your ENTIRE CSL collection and start over by downloading the latest plugin distribution and then downloading all of the HD CSLs again.

Why is this required? It's because most CSL models have their center point as either the CG or the nose of the aircraft, not the bottom of the tires. Consequently, if you tell the aircraft to draw at 0' AGL, the CENTER of the fuselage (about waist high for the pilot) will be at ground level. So, half the fuse will be underground along with the landing gear. As a result, we need the 'gear height offset' for EACH aircraft to know how much higher than ground level to draw the damned thing when it's time to float or clamp the airplane.

To be clear, the CSLs that now ship with the plugin as well as the HD CSLs that are available on the web site all have the required gear offsets. If you have 3rd party CSL libraries, you can still use them with PilotEdge, but the clamping code will not work well. I will see if I can disable the clamping logic for CSLs that do not specify any offset at all.

To check if a CSL has the gear offset, open the xsb_aircraft.txt file and look for the "OFFSET" line (if one is present at all). If it's there, the gear offset will be the THIRD parameter. If there are only TWO numbers (or no OFFSET at all), then there is no gear offset for that model.
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