Ballistics ( Bow - Arrow ) - is this Right?

Newbie & Debugging Questions
#1

Heya Guys!
Well im trying to make a little model of Ballistics to later implement in my game… I have something like this :

package balistica;

import com.badlogic.gdx.ApplicationListener;
import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.InputProcessor;
import com.badlogic.gdx.graphics.GL20;
import com.badlogic.gdx.graphics.Texture;
import com.badlogic.gdx.graphics.g2d.Sprite;
import com.badlogic.gdx.graphics.g2d.SpriteBatch;

/**
 *
 */
class View implements ApplicationListener, InputProcessor {

    private SpriteBatch batch;
    private Sprite ball;
    private Sprite box;

    private int boxPosX, boxPosY;
    public double ballPosX, ballPosY;

    private double angle;
    private double frameTime;

    @Override
    public void create() {
        Gdx.input.setInputProcessor(this);

        ball = new Sprite(new Texture(Gdx.files.internal("ball.png")));
        box = new Sprite(new Texture(Gdx.files.internal("cTest.png")));
        batch = new SpriteBatch();

        boxPosX = 10;
        boxPosY = 10;

        ballPosX = 0;
        ballPosY = 0;

        frameTime = -1;

    }

    @Override
    public void render() {
        Gdx.gl.glClearColor(0, 0, 0, 1);
        Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
        
        if (frameTime >= 0) {
            //getSX(double xo, double yo, double vo, double gravity, double angle, double time)
            ballPosX = Update.getSX(10,10,50,1, angle, frameTime);
            //getSY(double yo, double vo, double gravity, double angle, double time)
            ballPosY = Update.getSY(10,50, 1, angle, frameTime);

            System.out.println("x;y" + ballPosX + ";" + ballPosY);
            frameTime = frameTime + 0.1;
        }

        batch.begin();
        batch.draw(box, boxPosX, boxPosY);
        batch.draw(ball, (int) ballPosX, (int) ballPosY);
        batch.end();

    }

    @Override
    public void resize(int width, int height) {
    }

    @Override
    public void pause() {
    }

    @Override
    public void resume() {
    }

    @Override
    public void dispose() {
    }

    @Override
    public boolean keyDown(int keycode) {
        return true;
    }

    @Override
    public boolean keyUp(int keycode) {
        return true;
    }

    @Override
    public boolean keyTyped(char character) {
        return true;
    }

    @Override
    public boolean touchDown(int screenX, int screenY, int pointer, int button) {
        angle = Update.getAngle(boxPosX, screenX, boxPosY, screenY);
        System.out.println("Box = (" + boxPosX + ";" + boxPosY + ")");
        System.out.println("Screen = (" + screenX + ";" + screenY + ")");

        System.out.println("Angle" + angle);

        frameTime = 0;
        return true;
    }

    @Override
    public boolean touchUp(int screenX, int screenY, int pointer, int button) {
        return true;
    }

    @Override
    public boolean touchDragged(int screenX, int screenY, int pointer) {
        return true;
    }

    @Override
    public boolean mouseMoved(int screenX, int screenY) {
        return true;
    }

    @Override
    public boolean scrolled(int amount) {
        return true;
    }

}


package balistica;

public class Update {

    public static double getAngle(double xi,double xf, double yi, double yf) {
        double atan = Math.atan((yi-yf)/(xi-xf));

        return atan;
    }

    public static double getSX(double xo, double yo, double vo, double gravity, double angle, double time) {
        double dx = (xo + vo) * Math.cos(angle) * time;

        return dx;
    }

    public static double getSY(double yo, double vo, double gravity, double angle, double time) {

        double dy = (yo + vo) * (Math.sin(angle)) * (time - ((gravity / 2)) * (time * time));

        return dy;
    }

}

Im not sure its working… Would anyone have a look preety please?

#2

You’ll need to provide more details as to what the problem is. Sorry, I’m not going to sit here and try to guess what your code does.

#3

Ah im sorry,

well its a calculation to get the X;Y of the arrow after shooting it. It gets the angle and then you can use the angle to calculate.

#4
#5

It was incorrect. I still need to make some fixes but, heres what i changed so far :

package balistica;

public class Update {

    public static void main(String args[])
    {
        double angle = getAngle(20,200,20,200);
        System.out.println(angle);
    }
    
    public static double getAngle(double xi,double xf, double yi, double yf) {
        
        
        double atan = Math.atan((yi-yf)/(xi-xf));

        return atan;
    }

    public static double getSX(double xo, double yo, double vo, double gravity, double angle, double time) {
        double dx = (xo) + vo * Math.cos(angle) * time;

        return dx;
    }

    public static double getSY(double yo, double vo, double gravity, double angle, double time) {

        double dy = (yo) + vo * (Math.sin(angle) * time) - ((gravity / 2) * (time * time));

        return dy;
    }

}

package balistica;

import com.badlogic.gdx.ApplicationListener;
import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.InputProcessor;
import com.badlogic.gdx.graphics.GL20;
import com.badlogic.gdx.graphics.Texture;
import com.badlogic.gdx.graphics.g2d.Sprite;
import com.badlogic.gdx.graphics.g2d.SpriteBatch;

/**
*
*/
class View implements ApplicationListener, InputProcessor {

private SpriteBatch batch;
private Sprite ball;
private Sprite box;

private int boxPosX, boxPosY;
public double ballPosX, ballPosY;

private double angle;
private double frameTime;

@Override
public void create() {
    Gdx.input.setInputProcessor(this);

    ball = new Sprite(new Texture(Gdx.files.internal("ball.png")));
    box = new Sprite(new Texture(Gdx.files.internal("cTest.png")));
    batch = new SpriteBatch();

    boxPosX = 20;
    boxPosY = 20;

    ballPosX = 0;
    ballPosY = 0;

    frameTime = -1;

}

@Override
public void render() {
    Gdx.gl.glClearColor(0, 0, 0, 1);
    Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
    
    if (frameTime >= 0) {
        double vo = 60;
        double xo = 20;
        double yo = 20;
        double gravity = 10;
        //getSX(double xo, double yo, double vo, double gravity, double angle, double time)
        ballPosX = Update.getSX(xo,yo,vo,gravity,angle, frameTime);
        //getSY(double yo, double vo, double gravity, double angle, double time)
        ballPosY = Update.getSY(yo,vo,gravity, angle, frameTime);

        System.out.println("x;y" + ballPosX + ";" + ballPosY + "  at  " + "FrameTime : " + frameTime);
        frameTime = frameTime + 0.1;
    }

    batch.begin();
    batch.draw(box, boxPosX, boxPosY);
    batch.draw(ball, (int) ballPosX, (int) ballPosY);
    batch.end();

}

@Override
public void resize(int width, int height) {
}

@Override
public void pause() {
}

@Override
public void resume() {
}

@Override
public void dispose() {
}

@Override
public boolean keyDown(int keycode) {
    return true;
}

@Override
public boolean keyUp(int keycode) {
    return true;
}

@Override
public boolean keyTyped(char character) {
    return true;
}

@Override
public boolean touchDown(int screenX, int screenY, int pointer, int button) {
    angle = Update.getAngle(boxPosX, screenX, boxPosY, screenY);
    System.out.println("Box = (" + boxPosX + ";" + boxPosY + ")");
    System.out.println("Screen = (" + 200 + ";" + 200 + ")");

    System.out.println("Angle" + angle);

    frameTime = 0;
    return true;
}

@Override
public boolean touchUp(int screenX, int screenY, int pointer, int button) {
    return true;
}

@Override
public boolean touchDragged(int screenX, int screenY, int pointer) {
    return true;
}

@Override
public boolean mouseMoved(int screenX, int screenY) {
    return true;
}

@Override
public boolean scrolled(int amount) {
    return true;
}

}

#6

I just noticed that im stupid.

I forgot that in libgdx the Y is from the top to bottom.

SO…

 @Override
    public boolean touchDown(int screenX, int screenY, int pointer, int button) {
        System.out.println("Screen = (" + screenX + ";" + screenY + ")");
        screenY = Math.abs(Gdx.graphics.getHeight() - screenY);
        
        System.out.println("Fix ScreenY = " + screenY);
        angle = Update.getAngle(boxPosX, screenX, boxPosY, screenY);
        System.out.println("Box = (" + boxPosX + ";" + boxPosY + ")");

        System.out.println("Angle" + angle);

        frameTime = 0;
        return true;
    }
#7

why aren’t you using forces?
gravity force + some aerodynamic drag (just a force that pulles the arrow back, added to the plumes of the arrow)