To radians function

[webocs]

Description

Added a toRadians function and a corresponding demo for this Feature Request https://github.com/metafizzy/zdog/issues/34.

Changes

• Added toRadians function in Boilerplate.js
• Added a demo for the function
• Added new dist using makefile script

[desandro]

Thanks for this contribution! I'm still evaluating if this feature is worth adding to Zdog and how. I think I may prefer Chris Gannon's suggestion of setting a Zdog-wide property like useDegrees. Otherwise, doing this conversion can be done on developer-side, with either your own helper function or inline:

rotate: { y: 45/360 * Zdog.TAU }

[webocs]

I see! no problem, this was pretty straightforward so I figured I could PR it even if it wasn't used!. Are you planning on converting to radians for each operation if the variable is set, thus leaving the engine as it is now. Or are you planning to change the math of the rotateProperty function?

function rotateProperty( vec, angle, propA, propB ) {
  if ( !angle || angle % TAU === 0 ) {
    return;
  }
  // It could be as simple as this??.  unless you want to change the math
  angle =  useDegrees? angle/360 * Zdog.TAU : angle;

  var cos = Math.cos( angle );
  var sin = Math.sin( angle );
  var a = vec[ propA ];
  var b = vec[ propB ];
  vec[ propA ] = a*cos - b*sin;
  vec[ propB ] = b*cos + a*sin;
}

[desandro]

Yeah, I was thinking a library-wide change in rotateProperty. I'm waffling on this feature as it feels un-Zdog-like in that its extra stuff for personal preference. I'm now thinking a good approach is to make rotateProperty a proper Vector method so you could duck punch it.

// if Vector.prototype.rotateProperty were a thing
Zdog.Vector.prototype.rotateProperty = function ( angle, propA, propB ) {
  if ( !angle || angle % 360 === 0 ) {
    return;
  }
  angle = angle / 360 * Zdog.TAU;
  var cos = Math.cos( angle );
  var sin = Math.sin( angle );
  var a = vec[ propA ];
  var b = vec[ propB ];
  this[ propA ] = a*cos - b*sin;
  this[ propB ] = b*cos + a*sin;
};

Another solution is to add type checking. Any string ending with deg would be treated as a degree. You could pass in '180deg'. So Zdog would support both degrees and radians interchangably.

function rotateProperty( vec, angle, propA, propB ) {
  var isDegree = typeof angle == 'string' && angle.match( /deg$/ );
  if ( isDegree ) {
    angle = parseFloat( angle ) / 360 * TAU;
  }
  if ( !angle || angle % TAU === 0 ) {
    return;
  }
  var cos = Math.cos( angle );
  var sin = Math.sin( angle );
  var a = vec[ propA ];
  var b = vec[ propB ];
  vec[ propA ] = a*cos - b*sin;
  vec[ propB ] = b*cos + a*sin;
}

[webocs]

The second option sounds great and more natural if you ask me. I imagine some people copying demos from the internet that won't work because they missed the config line at the beginning. This approach will eliminate that hazard.

[chrisgannon]

I think passing a string like '180deg' is cumbersome and unnecessary - passing a number for degrees would be ideal.