3 Dimensional projectiles

[icarus_uk]

Ok I have a script, and its not working!  The idea of the script is that it creates a shell at a position (_Launcher) and "shoots" it as a target (_target).



;Get the name of the target, the launcher, the type of munitions and the flight time

_Target = _This Select 0;
_Launcher = _This Select 1;
_shelltype = _This Select 2;
_FlightTime = _This Select 3;

#Fireone

;Get the difference in X co-ordinate (East/West)

_Xdistance = (Getpos _Target Select 0) - (Getpos _Launcher Select 0);



;Get the difference in Z co-ordinate (North/South)

_Zdistance = (Getpos _Target Select 1) - (Getpos _Launcher Select 1);



;Get the difference in Y co-ordinate (Up/Down)

_Ydistance = (Getpos _Target Select 2) - (Getpos _Launcher Select 2);



;Calculate the planar angle of attack, measured clockwise from the positive X axis

_planarangle = _Zdistance/(tan _Xdistance);



;Create the first projectile round slightly above the launcher.

_shell1 = _shelltype Camcreate [Getpos _Launcher Select 0, Getpos _Launcher Select 1, (Getpos _Launcher Select 2)+1]



;Give the Shell the correct velocity

_Shell1 SetVelocity [_Xdistance/_FlightTime, _Zdistance/_FlightTime, (_Ydistance- (0.5*(-9.*(_FlightTime^2)))/_FlightTime ];

~4

Goto "Fireone"

Now the script works at close range.  But over long distances the shells are falling short (very short).  I have a feeling its the Y velocity, but cant get my brain around the correct line.

[icarus_uk]

Cmon people, 14 views (15 now) and no replies? Have you all gone sissy?!  

I just had a brain fart,  does flashpoint model air resistance?

[icarus_uk]

Cmon peeps, this has been up 20 hours!  Heeeeelllllpppppp meeeeee  Im meeellllttttiiinngggg!

Ive had another brain fart!

If the position launcher is on the ground, and the target is on a hill 40 metres higher than the target, but also still on the ground, will both their Y co-ordinates be 0 ?

[LCD]

i like ur brain farts Icarus  

yes da getpos unitname select 2 - gives alwayz 0 4 men and 4 tanks (im not sure bout da tanks)

u need 2 find da altitude above sea level 4 both (i think ;D)

try dat function and mebe it wil work :wow: ;D

LCD OUT

[edit] - k da thing goes like dat  

da getpos unit select 2 alwayz gives high above ground - but if u try it on Tanks (and prooly soldiers and not armored vehicles - but im not sure) it gives less dan 1 alwayz

[Noon416]

I wouldn't say you need to adjust for "air resistance", so much as just adjusting for gravity alone, which is definitely modelled by the engine.

You'd need to find/create a function to either:
- adjust projectile velocity to scale with the distance to target, or;
- adjust the projectiles firing elevation to compensate for the increased drop over the larger distance.




Hope that helps, as I've just done serious damage to the last remaining brain cells I had ...

[icarus_uk]

As far as I know, Im already doing that.   Using the dynamics exquation;

(Initial Velocity) = (Displacment) - 0.5 * (acc of gravity) * (Flight Time) ^ 2 / (Flight Time)

Using that in each of the 3 axis (in the X and Z the acc due to gravity is 0) should make the projectile land on the target every time,  assuming of course that there is no drag caused by air resistance.

[Doolittle]

Welcome to OFP physics.  There is drag.

I couldn't figure it out.  This is as far as I got:

_dx = ((_pos select 0) - (_src select 0))
_dz = ((_pos select 1) - (_src select 1))
_dist = sqrt ((_dx ^ 2) + (_dz ^ 2))

_dir = _dz atan2 _dx
_angle = 20
_muzzle = sqrt (9.8 * _dist / sin (2 * _angle))

_vy = _muzzle * sin _angle
_hyp = _muzzle * cos _angle
_vx = _hyp * cos _dir
_vz = _hyp * sin _dir

_shell = _type createVehicle [_src select 0, _src select 1, 2]
_shell setVelocity [_vx, _vz, _vy]

Doolittle

[icarus_uk]

Thats all very frilly.  Mind explaining what the heck it means?

[LCD]

y not just cheat da engine ? ;D

use looped setpos   ;D

LCD OUT

[icarus_uk]

cause thats cheating!

Do tank shells still make that whistling noise when they are setpossed?  Either way, Id still like to work out the air resistance.

Doolittle, any help on understanding, and implementing your script there?

[Doolittle]

Actually mine does what you are doing, but you are doing it in a much nicer way.  I think they're both the same.

I have been working on combatting air resistance for a couple days now.  One thing I did that comes CLOSE is to cheat and have a loop with the shell until it explodes, in that loop you set the X and Z velocity to the same initial X and Z over and over.  This removes the DRAG from the horizontal movement, but now still need to "negate" the Y friction.

Doolittle

[KTottE]

This is teh advanced scriptarz, so I moved it here.

I'm way too tired to wrap my head around the maths involved here, but from a quick glance, Doolittle is on to something.
I suggest checking CareyBear's posts over on the official forum, he was working on a script similar to this.