TraceLine/Intersection - Collision detection with height limit

[Frosttall]

Hey guys,

I'm currently working with Intersection and as you know do the maps have a height-limit, which is done with something like an invisible wall.

Even after trying various flags I'm at a loose end and I'd like to know if someone else already found the correct flag to check this.

Thank you

[Bananenbrot]

I would guess that the height limit is hard coded. Have you tried to measure your z coordinate in different places while flying at that border?
In that case you can just check the z of your end point of the intersection test if there were no other intersections.

[Frosttall]

Yes I've tried that already and it doesn't depend of the zone or something like that. For example can you see in the Twilight Highlands that this value isn't constant for a complete zone, because as more as you go to the east, as lower it becomes.

I'm pretty curious how the client detects that it collides with this wall.

[Bananenbrot]

Ok... flight boxes are definitely stored in the AFBO chunk. So start from CGUnit_C__PlayFlightBoundsFeedback, I'll go through it too and will post my findings.

Edit: Rubbish... ADT v23 isn't used in release. But nonetheless it's the right track. And of course, you could simply parse the MFBO chunk of the adt. But where is the fun in that?

Edit2: Okay, they compute the adt tile coordinate of your position and then calculate the maximum z which is allowed based on the planes given in MFBO. I don't know if they are unmodified or a z offset is added while parsing the adt... regardless, MFBO provides you with 2 planes à 3*3 z values (in a grid). They compute in which quarter of the adt you are and then perform the z calculation based on the plane equation... basically z = -(x*n1 + y*n2 - d) / n3, where (x, y, z) is the player's position (or rather his highest/lowest possible position at (x, y)). (n1, n2, n3) is the plane's normal of length 1. d is a value which you get if you solve the equation for a point in the plane (basically, a distance measurement to (0,0,0)). This is math, so look here. This is the easiest way I can think of (except for calling an ingame function).

Edit3: Ahh, you are injected... Then it is as simple as calling

BOOL __cdecl World::GetFlightBoundsUpper(const C3Vector& position, float& fbo)

at 0x7243C0 (not rebased).