UFO Flight Patterns

(Zaimoni: Some working notes. This plausibly should be moved to mainline when sufficiently detailed. While I do use MISSIONS.DAT notation to index the UFOs, this does not belong there.)

Common observations:

• In spite of the game having precomputed trig functions at 1/8 ° resolution, the "turning points" are not nearly so densely packed. (I suspect a sparse latitude-longitude grid, or an explicit valid list somewhere.) It should be possible to identify the precise intermediate destination in-game, at least when it's near the equator and not at the same latitude. UFOs are notably slower at turning points.
• When a UFO leaves its target region, it's leaving for good.
• The next "turning point" (or landing site, as the case may be) is only generated when the current one is reached.
• I have not been able to get a Retaliation mission scheduled when a UFO is shot down at the second or later "turning points". Scheduling is very unreliable even then, and is not a strict matter of either speed or accuracy.

Retaliation searching UFOs

• Searching Retaliation UFOs (before BattleShip) fly slow. With XComUtil craft, it may be possible to shoot them down with a Skyranger.
• Searching Retalation Battleships merely fly "normally".

I am tentatively assuming that the number of turning points is fixed, but that they may not necessarily be visible to the naked eye because of practical colinearity.

Research 0/0

• These do not land.
• Four turning points, leave.

Research 1/0

• Four turning points, land, leave.

Terror 0/0

• three turning points, land, three turning points, land, leave

Retaliation 0/0

• These do not land.
• five turning points, leave. (Didn't get a clear sample)

Retaliation 1/0

• These do not land.
• seven turning points, leave. The one I observed to count this did a very tight zigzag pattern...it would have touched any base in about 2/3rds of the nation of South Africa, and just about any base in Madagascar.