Print Page - Calculating angle from 2d point A to 2d point B

Title: Calculating angle from 2d point A to 2d point B
Post by: amoeba on August 20, 2004, 13:13:20

Currently my 'ships' in my game move using an x, y, velocity and angle variable. I want to be able to point at 'something' with the angle vector - i.e. another ship.

Is there an algorithm to give me Angle from x1,y2,x2,y2?

Thanks.

Title: Calculating angle from 2d point A to 2d point B
Post by: tomb on August 20, 2004, 14:11:18

Code Select


	/** Gets the angle of the vector given by (xp, yp)
	 */
	public static final double getAngleFromVector(double xp, double yp)
	{
		if ((xp!=0)&&(yp!=0))
	    {
    		//Calculate angle of vector
    		double angle=0;
    		if (xp!=0)
    		{
    			if ((xp>=0)&&(yp>=0))
    				angle=Math.atan(yp/xp);
    			if ((xp<0)&&(yp>=0))
    				angle=Math.PI-Math.atan(yp/-xp);
    			if ((xp<0)&&(yp<0))
    				angle=Math.PI+Math.atan(-yp/-xp);
    			if ((xp>=0)&&(yp<0))
    				angle=Math.PI*2-Math.atan(-yp/xp);
    		}
    		else
    		{
    			if (yp>=0)
    				angle=Math.PI/2;
    			else
    				angle=Math.PI+Math.PI/2;
    		}
    		return angle;
		}
		else
		{
			if (xp==0 && yp==0) return 0;
			if (xp==0 && yp>0) return Math.PI*0.5;
			if (xp==0 && yp<0) return -Math.PI*0.5;
			if (yp==0 && xp>0) return 0;
			else return Math.PI;
		}
	}

Title: Calculating angle from 2d point A to 2d point B
Post by: princec on August 20, 2004, 14:38:37

Doesn't Math.atan2() do all that for you in one call?

Cas :)

Title: Calculating angle from 2d point A to 2d point B
Post by: amoeba on August 20, 2004, 14:47:48

And to use that its;

getAngleFromVector( source.x-target.x, source.y-target.y)

?

Title: Calculating angle from 2d point A to 2d point B
Post by: amoeba on August 20, 2004, 15:06:38

Aaah excellent thanks.

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Programming => Lightweight Java Gaming Library => Topic started by: amoeba on August 20, 2004, 13:13:20