#How to track arrow position in minecraft for graphing as quadratic function (without drag)?

1 messages · Page 1 of 1 (latest)

pale turtle
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not really, but i assume its quite counterintuitive. I guess the easiest way to do it would be to just run the "tracker" on repeat through the whole motion.. not really sure how to do that tho

hearty igloo
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nah it's not counterintuitive dw

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tl;dr is

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thing happens in game (someone shoots a bow) -> server fires event (ProjectileLaunchEvent) -> anything set up to listen for ProjectileLaunchEvent runs the relevant code in an event handler

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it's like if you fire a gun in a suburban area the police show up

pale turtle
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xD

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that makes sense

hearty igloo
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are you trying to get the real trajectory of the arrow or just convert its launch velocity and angle to an equation?

pale turtle
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i mean it should be the same

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bc i have eliminated drag

hearty igloo
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er, by real i mean

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if it hits a block midway, though that wouldn't fundamentally change the equation that maps its position

pale turtle
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the issue is i need all (at least the max and zero points) to be able to graph it as cuadratic

hearty igloo
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if you're only trying to do the latter, then you don't need to track its position at all

pale turtle
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id be doing it on a superflat anyways

hearty igloo
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aye

pale turtle
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its for a math project

hearty igloo
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okay that clears things up lmao

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uh

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thinking

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so basically you need to have the equation in X/Y/Z

pale turtle
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yeah

hearty igloo
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you can decompose it to a linear system

pale turtle
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id do only x and y or z and y

hearty igloo
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since all 3 components are independent of one another, I mean

pale turtle
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shooting the arrow as if it was a 2d plane as to9 not overcomplicate

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(straight liine not diagonal within the x/z axis)

hearty igloo
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Since drag doesn't matter, your X and Z won't really be all that important here

pale turtle
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wdym

hearty igloo
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like

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Sorry I should clarify - your X and Z velocities will remain constant, so you really only need to worry about your Y velocity

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since gravity

pale turtle
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oh yes

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yes

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honestly velocity isnt my priority anyways

hearty igloo
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tl;dr you can do this without needing to track the arrow, i'd argue trying to generate a best fit parabola for a set of points would actually be harder lol

pale turtle
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bc im just graphing the position\

hearty igloo
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especially with a low tickrate

pale turtle
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hmm

hearty igloo
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well, you can do two things

pale turtle
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fair poinmt

hearty igloo
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  1. obtain parameterized launch velocity in terms of time t with respect to x/y/z (i phrased this badly)
  2. use a timer to find the real time in flight for any given arrow
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You actually don't even have to do that much trig here, velocity is stored as a 3d vector on entities so you don't even have to worry about converting the direction vector

pale turtle
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yes

hearty igloo
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...that wouldn't be that hard either, come to think of it LOL i think this is entirely trig-agnostic since rotation/etc. is handled already

pale turtle
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yeah true

hearty igloo
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i'm p sure velocity is per tick

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and instantaneous in a given tick

pale turtle
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yes i think it is

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again i think its even simpler given that i only need the arrow's position

hearty igloo
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what you can honestly do is uh

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run that timer, right

pale turtle
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yeah

hearty igloo
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and just feed the time into the equation you have

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so like if the arrow starts out with a velocity of 10, 10, 10 and is in flight for 20 ticks (1 second)

pale turtle
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i see what you mean

hearty igloo
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you'd just do 10 * 20 for both x/z

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and then for y you'd want to factor in acceleration, which is just 1m/t^2

pale turtle
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however i dont have an equation yet

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for the parabola

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id probably get that from the actual position

hearty igloo
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well the launch position can tell you everything you need to know

pale turtle
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true

hearty igloo
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since that'll tell you what the x/y/z offsets are for one point on the parabola

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my main concern with tracking its position is gonna be

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minecraft servers run at 20 ticks per second

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it's very likely you'll miss the actual maximum of the parabola

pale turtle
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ohh

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yeah youre right

hearty igloo
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like it'd be simpler to track the arrow's position, sure

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but like for an arrow where you launch it at a relatively gentle angle, it'll pass the maximum at considerable speed

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this may help you

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this is like, physics 101

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kinematics

pale turtle
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ye ye im in physics HL

hearty igloo
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vf = final velocity
vi = initial velocity
delta x = change in position on that axis
a = acceleration

pale turtle
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however

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if the arrow only moves in each tick, wouldnt it reach the maximum during a tick?

hearty igloo
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depends on how the server handles things

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see

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the server only updates during a tick

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a good way to showcase what i'm talking about is uh

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make an arrow tracker and have it just spawn a particle at the arrow's location every tick

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you'll see how jank it is

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but you as the player will see the arrow moving smoothly

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that's because the game interpolates the arrow's location in the render loop

pale turtle
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true

hearty igloo
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otherwise you'd have every arrow moving at 20 fps

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it'd look like shit

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not just arrows -every entity

pale turtle
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yeah i see what you mean

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so ig its more convenient to go for the velocity approach?

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as the slope in the quadratic function x over y is going to be v anyways

hearty igloo
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quadratics don't have a slope, wym

pale turtle
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i mean

hearty igloo
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they have tangents

pale turtle
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like slope at a specific given point

hearty igloo
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yeah

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okay you meant those

pale turtle
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thats what i menat

hearty igloo
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wait what level of maths is this

pale turtle
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yes

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basic

hearty igloo
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okay so there's no calculus involved here

pale turtle
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nono

hearty igloo
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was gonna say if you wanted the arrow's velocity at any given point, velocity is a derivative of position and you could just write something really basic to derive it for the y component but that's outside the scope of this project

pale turtle
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yeah

hearty igloo
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so yeah for the core of what you're doing here

pale turtle
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however for that youd still need the position no?

hearty igloo
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nah

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not the exact position

hearty igloo
pale turtle
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i know how the speed is going to change given mcs gravity

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assuming it is vertical speed not horizontal

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use that and initial position to get the position at time t

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then i can probably js graph x/t

pale turtle
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anyways, thank you very much for the help. I'll let you know how it goes. Cya!

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How to track arrow position in minecraft for graphing as quadratic function (without drag)?

hearty igloo
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public class Trajectory {
  private float vx, vy, vz;
  static final float GRAVITY = -1.0f; // not where i'd put this, but for the sake of example
  public Trajectory(float vx, float vy, float vz) {
    this.vx = vx;
    this.vy = vy;
    this.vz = vz;
  }

  // returns the arrow's change in position t ticks after launch
  public Vector evaluate(float t) {
    // very simple since you don't have anything acting on vx/vz
    float dx = vx * t;
    float dz = vz * t;

    float dy = vy * t + 0.5f * GRAVITY * t * t;
    return new Vector(dx, dy, dz);
  }
}```
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something like that

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sorry i was afk

hearty igloo
pale turtle
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Ok

pale turtle
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I tried using eclipse with a code by chatgpt and just couldnt get it to work

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Apparently eclipse wasnt recognising my spigot 1.17 jar file so it kept showing errors

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I js need a way to implement it in mc

hearty igloo
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how new to programming are you?

hearty igloo
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chatgpt is shit

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you will not learn by using it

pale turtle
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Lol good point

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Mostly was a last resort

pale turtle
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😭

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How could i add the projectilelaunchevent detection to the game (just to get that initial position then its all math) to run it on a server?

hearty igloo
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very bare bones tutorial

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all you need

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incidentally