Cheat Engine

zm0d · Posted: Mon May 23, 2016 8:53 am Post subject: Flying object - prediction line

Hi

lets assume I have an object like an arrow that gets shot by a bow.

How can I calculate and draw a "prediction" line for this flying arrow?

Is there usually a data array that gets filled as soon as I shoot the arrow in the air with all the 3D position structures?

Would I read this array and then draw points on the screen regarding to all the positions I find in-memory?

++METHOS · Posted: Mon May 23, 2016 4:07 pm Post subject:

It depends on that target and how that data is being handled. For most games, the projectile has xyz coordinates, just like everything else. Also, if you have a reticle or crosshair (visible or not), these may also have xyz coordinates for 3-D and/or xy values for 2-D coordinates. In other words, you can determine where your arrow is going to go, three-dimensionally, before you even shoot it.

The xyz may not exist for the projectile until you fire your weapon. However, the xyz for reticle/crosshair etc. may always be present.

Not all games handle the data in this way, however.

mgr.inz.Player · Posted: Mon May 23, 2016 4:24 pm Post subject:

Mostly, projectile trajectory is calculated on the fly.

Assuming game has modern engine, like Unreal Engine, you can expect that for each arrow game will keep position (x,y,z), velocity vector (Vx,Vy,Vz) and acceleration vector (Ax,Ay,Az).

If game also takes aerodynamics into account, there will be additional factors.

https://en.wikipedia.org/wiki/Trajectory_of_a_projectile

hhhuut · Posted: Mon May 23, 2016 4:25 pm Post subject:

Depending on the game you may also have to take the game's physics into your calculation ...

zm0d · Posted: Tue May 24, 2016 2:11 am Post subject:

ParkourPenguin · Posted: Tue May 24, 2016 8:58 am Post subject:

zm0d · Posted: Tue May 31, 2016 8:58 am Post subject:

I also could use the games projectile trajectory function, or?
I guess I would need to use the games projectile trajectory function, because of collision/rebound from walls?

I would have to add a time factor to the projectile trajectory function, or? I mean it's not very helpful to know, where my projectile is in the next frame. It would be more useful to know, where it is in the e.g. 5 next seconds.

ParkourPenguin · Posted: Tue May 31, 2016 9:24 am Post subject:

Unless the game literally displays a prediction line for you to see, you have no basis to assume the game knows exactly where the projectile is going more than a frame or two in advance.

Take pong as a very basic example. The computer can't easily predict human movements- the ball could bounce off the paddle or it could go right past it if the paddle isn't in the way. Thus, it's impossible for the computer to predict where the ball will be many, many frames in advance of where it is now (I'm not going to take into account Schrödinger's cat; it would only play with the ball). However, the computer can predict where the ball will be in the next frame quite nicely, as it can check to see if the paddle is in the way right now.

If the system you're talking about is completely deterministic, free of any randomness or outside interference, then you can calculate where the projectile will be many seconds in advance. I'd guess most games don't take into account air resistance and simply use a quadratic equation as a basis for projectile motion calculations. Since the game likely calculates it every frame, you should loop through whatever equation(s) the game uses for projectile motion however many times you need to calculate it however many frames in advance you need it. Finding that subroutine might be hard, and it's usually viable to guess what the constants are and make your own through trial and error.