radians and degrees conversion

[casey]

I'm thoroughly confused about radians and degrees! Been a long time since high school math

I'd like to get the rotation of an object (currently being returned in radians),  convert that to degrees, and allow for a variance of a few degrees. So a player is rotating the object to line it up with another object, and I'm checking that the rotation is correct. 

The rotation should be 180 deg, give or take a few degs (so 175 to 185 deg). 

However, my rotation is converting as where approx 185 is shows up as -175... Basically once it hits 180 it converts into a negative number, backwards from 180.

I've got 

this.rot = rotationOfSprite;


var degs = this.getDegrees(this.rot);
console.log(degs);



getDegrees: function(){
   var degs = this.rot * 180/Math.PI;
   return degs;
}

 

 

 

SOLVED. Figured it out. Thanks (future ref:  if(this.rot<0) this.rot +=2*Math.PI.

[sebas86pl]

Most game engines have somewhere in code constants and just multiply values to perform conversion:
 

var rad2ang = 180/Math.PI;
var ang2rad = Math.PI/180;

/* [...] */

var angle = someObject.rotation /* in radians */ * rad2ang;

In this case you can easily avoid function call and code is still perfectly readable.

[casey]

Thank you: but does that account for the fact that the degrees here aren't  360, but 180 and -180   (which is why I had to resort to if(this.rot<0) this.rot +=2*Math.PI.)?

[sebas86pl]

It doesn't matter if it's range of <-180,180> or <-360-360> or even bigger values, it just works because trigonometric functions are periodic functions and math lib can handle it. You should just avoid extremely big values to avoid precision loose.

[mattstyles]

Most libraries also cache values (at least integer rotational values) and save themselves some processing cycles.