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  [Java 2D FINAL Projectile Angle?] *solved*  (Read 759 times)
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Offline GabrielBailey74
« Posted 2013-01-17 01:09:48 »

Hello JGO, for the past few days I've been working on a new project. Roll Eyes

Happy to say that the fancy side of the project is done, added a animated background, loading screen, audio, lighting etc.
Now I'm at the point where I've implemented a 'Game Screen', at the moment it's just a moveable player, a 'Gun' that rotates towards the mouse:

(Can't see it in this picture, but there is a 'Sights Cursor' for aiming present)


At the moment, when the mouse is pressed I am adding a 'Projectile' to a LinkedList<Projectile> like so:
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final int centerX = absX + width / 2;
final int centerY = absY + height /2;
final Projectile t = new Projectile(centerX, centerY);
final double angle = Math.atan2(centerY - mX, centerX - mY); // mX standing for MouseX
t.setAngle(angle);
t.setVelX(8.0);
t.setVelY(8.0);
projectiles.add(t);


Final code Snippet is from the Projectile class, this method is polled in the Game Loop:
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/* Moves the Projectile correctly */
public void tick() {
   theta = Math.toRadians(angle);
   nextX = x + (velX * PROJETILE_SPEED) * -Math.cos(theta + Math.PI / 2);
   nextY = y + (velY * PROJETILE_SPEED) * -Math.sin(theta + Math.PI / 2);
   x = nextX;
   y = nextY;
}


The Issue that I'm having is:
After I set the Projectiles angle (Calculated off of the mouse's coordinates), if I proceed to move the mouse while the projectile's in motion, it Override's the first angle I set for that projectile?

Notes:
I've tried in the 'tick()' method only initializing the 'theta' once, that didn't work, it still resets the final angle to where the mouse currently is.
Hope somebody can help me, I'm not too familiar with radians etc, the issue seems to be 'constantly updating the angle'.

Offline HeroesGraveDev

JGO Kernel


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Exp: 3 years


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« Reply #1 - Posted 2013-01-17 01:28:24 »

Make it a feature!! Grin

EDIT: If you want to ignore ^that^ then try this:

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    nextX = x + (velX * PROJETILE_SPEED) * -Math.cos(theta); // REMOVED "+ Math.PI / 2"
    nextY = y + (velY * PROJETILE_SPEED) * -Math.sin(theta); // REMOVED "+ Math.PI / 2"


But you should seriously consider making this "glitch" a main feature of the gameplay. It could be quite interesting.

Offline GabrielBailey74
« Reply #2 - Posted 2013-01-17 01:43:54 »

Make it a feature!! Grin

EDIT: If you want to ignore ^that^ then try this:

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    nextX = x + (velX * PROJETILE_SPEED) * -Math.cos(theta); // REMOVED "+ Math.PI / 2"
    nextY = y + (velY * PROJETILE_SPEED) * -Math.sin(theta); // REMOVED "+ Math.PI / 2"


But you should seriously consider making this "glitch" a main feature of the gameplay. It could be quite interesting.

Thanks for the reply Wink, I 'almost' / 'temporarily' fixed it by increasing the velocity of it lolz, gives it no chance to modify it's angle before it's hit it's target.

EDIT
: The reason i had
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+ Math.PI / 2
is because that's what fixed it's angle.
If i remove that, the angle isn't relative to the mouses coordinates at all.
The Projectile just slams in some awkward angle o.O

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Offline HeroesGraveDev

JGO Kernel


Medals: 291
Projects: 11
Exp: 3 years


┬─┬ノ(ಠ_ಠノ)(╯°□°)╯︵ ┻━┻


« Reply #3 - Posted 2013-01-17 02:01:26 »

EDIT: Switch cos() and sin() around and then remove + Math.PI / 2.

Offline GabrielBailey74
« Reply #4 - Posted 2013-01-17 03:49:05 »

Thanks mate, everything's perfect naow with mah angles Grin
Looks like I need to learn more about translating the Projectiles coordinates for collision now Stare

I thought it would be like:
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void tick() {
     if (x >= GameWindow.WIDTH) { visible = false;
}


But I know I have to do more than that lol, it's cutting the projectiles off at weird distances o.O

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