[Solved] Handling movement

Newbie & Debugging Questions
#1

So I know this is a mega newbie question, but I am trying to use an angle and hypotenuse to calculate the delta x and y.

Diagram:

The blue dot is a point that I already know, the 5 is a constant, and I know the angle theta. I just need to get dx and dy. My LWJGL is setup so that y 0 is at the top. The player’s position is a vector2f, and I just need to add the that vector.

My code so far:


float speed = Launcher.getSpeed();
float angle = getAngle(player.x, player.y);
if(Input.isKeyDown(Keyboard.KEY_W)){
	float dx = speed * (float) Math.sin(Math.toRadians(angle));
	float dy = speed * (float) Math.cos(Math.toRadians(angle));
	player.x -= dx;
	player.y -= dy;
}

Again, sorry for such a newbie question!

CopyableCougar4

#2

Is that really where the angle is? Is the blue dot the player, or what?

Either way, you have sin and cos switched for x and y.

#3

The angle is there, so I had to switch sin and cos for which side was opposite and adjacent.

CopyableCougar4

#4

To be honest if you know the distance from the point to the player then its much more efficient to just figure out the DX and DY through the equation of a straight line y = mx where m is the local variable in a loop , x is the gradient (Playery - pointy)/(Playerx - pointx) and y is y of course. If you then wanted to apply this to transforming your player position you would do transformfunction(m,y); As m is the increment and y is being increased by the increment * gradient. For implementing speed you would for example


float gradient = (Playery - pointy)/(Playerx - pointx);//calculate the gradient
for(int i = 0; i < (Playerx - pointx); i+=speed){//only go on for the distance (you might want to add checks because of that speed variable.
    transformfunction(i + Playerx,(i * gradient) + Playery);//apply the transformation.
}
#5

So I guess the issue is mostly solved, here is the code:


private Vector2f scratch = new Vector2f(); // Scratch vector
	public void move(float angle){
		float theta = (float) StrictMath.toRadians(360.0f - angle);
		float hypotenuse = 1.0f * Launcher.getSpeed();
		float dx = (float) Math.sin(theta) * hypotenuse;
		float dy = (float) Math.cos(theta) * hypotenuse;
		Vector2f.add(player, new Vector2f(-dx, -dy), scratch);
		if(map.collision(scratch, new Rectangle(0, 0, 100, 100))){
			Vector2f.add(scratch, new Vector2f(dx, dy), scratch);
		}
		player.set(scratch);
	}

To actually call this function


float angle = getAngle(Launcher.getWidth() / 2, Launcher.getHeight() / 2);
			if(Input.isKeyDown(Keyboard.KEY_W)){
				move(angle);
			}
			if(Input.isKeyDown(Keyboard.KEY_S)){
				move(180.0f + angle);
			}

CopyableCougar4