Get angle from 2 positions

Question

I have 2 objects and when I move one, I want to get the angle from the other.

For example:

Object1X = 211.000000, Object1Y = 429.000000 Object2X = 246.500000, Object2Y = 441.500000 

I have tried the following and every variation under the sun:

double radians = ccpAngle(Object1,Object2); double degrees = ((radians * 180) / Pi);  

But I just get 2.949023 returned where I want something like 45 degrees etc.

Answer 1

Does this other answer help?

How to map atan2() to degrees 0-360

I've written it like this:

- (CGFloat) pointPairToBearingDegrees:(CGPoint)startingPoint secondPoint:(CGPoint) endingPoint {     CGPoint originPoint = CGPointMake(endingPoint.x - startingPoint.x, endingPoint.y - startingPoint.y); // get origin point to origin by subtracting end from start     float bearingRadians = atan2f(originPoint.y, originPoint.x); // get bearing in radians     float bearingDegrees = bearingRadians * (180.0 / M_PI); // convert to degrees     bearingDegrees = (bearingDegrees > 0.0 ? bearingDegrees : (360.0 + bearingDegrees)); // correct discontinuity     return bearingDegrees; } 

Running the code:

CGPoint p1 = CGPointMake(10, 10); CGPoint p2 = CGPointMake(20,20);  CGFloat f = [self pointPairToBearingDegrees:p1 secondPoint:p2]; 

And this returns 45.

Hope this helps.

Answer 2

Here's how I'm doing it in Swift for those interested, it's based on @bshirley's answer above w/ a few modifications to help match to the calayer rotation system:

extension CGFloat {     var degrees: CGFloat {         return self * CGFloat(180) / .pi     } }  extension CGPoint {     func angle(to comparisonPoint: CGPoint) -> CGFloat {         let originX = comparisonPoint.x - x         let originY = comparisonPoint.y - y         let bearingRadians = atan2f(Float(originY), Float(originX))         var bearingDegrees = CGFloat(bearingRadians).degrees          while bearingDegrees < 0 {             bearingDegrees += 360         }          return bearingDegrees     } } 

This provides a coordinate system like this:

        90 180              0         270 

Usage:

point.angle(to: point2) CGPoint.zero.angle(to: CGPoint(x: 0, y: 1)) // 90