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 Simpler way to calculate angle between two points?  (Read 3791 times) 0 Members and 1 Guest are viewing this topic.
appel

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 « Posted 2006-01-02 06:20:01 »

I'd like to know if there is a simpler way to calculate the angle between two points.

I'm currently using this method:

 1  2  3  4  5  6  7  8  9  10  11  12  13  14  15  16  17  18 public static float angle(float x1, float y1, float x2, float y2)    {        float dx=x2-x1,dy=y2-y1, PI=(float)Math.PI;        double angle=0.0f;                if(dx==0)           if(dy==0)angle=0;           else if(dy>0)angle=PI/2;           else angle=PI*3/2;        else if(dy==0)           if(dx>0)angle=0;           else angle=PI;        else if(dx<0)angle=Math.atan(dy/dx)+PI;        else if(dy<0)angle=Math.atan(dy/dx)+(2*PI);        else angle=Math.atan(dy/dx);        return (float)angle;    }

Seems like a awful alot for something simple as that.

I'd like the angle to be 0 at 3 o'clock, and moving clockwise it should be PI at 9 o'clock. Any ideas?

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kul_th_las
Guest
 « Reply #1 - Posted 2006-01-02 07:32:03 »

I would write it slightly different, but I think what you've got there is as simple as it gets when you're starting with a pair of (x, y) coordinates.

You could change your logic around a bit so you don't have so many if/then/else statements, but it doesn't look like you're doing any wasted work.
kevglass

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 « Reply #2 - Posted 2006-01-02 13:05:32 »

Math.atan2() does this doesn't it?

Kev

woogley
 « Reply #3 - Posted 2006-01-02 13:09:30 »

 1  2  3 protected double calcAngle(Point p1,Point p2) {     return Math.atan2(p2.y-p1.y,p2.x-p1.x)*180.0/Math.PI;}
appel

JGO Wizard

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 « Reply #4 - Posted 2006-01-02 13:31:16 »

Amazing, thanks kev and woogley. That was exactly the *simplicity* I was looking for

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