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Compare new setRotationCenter values after truncating to 32bit

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`Skin._rotationCenter` is a twgl vector or said another way a
Float32Array. JavaScript casts values stored in this array as 32 bit
floats instead of JavaScript's standard 64 bit floats. Comparing the
equality, like `setRotationCenter` does, of a 64 bit float against a
value stored in a 32 bit container will virtually always be false.
Truncating the new value into a 32 bit (losing precision) will give a
more useful comparison and remove a lot of current false positives.
This commit is contained in:
Michael "Z" Goddard 2017-11-07 17:18:23 -05:00
parent 998d3e129a
commit b060c07db1
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GPG Key ID: 762CD40DD5349872
1 changed files with 18 additions and 1 deletions
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19
src/Skin.js
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@ -4,6 +4,19 @@ const twgl = require('twgl.js');
const RenderConstants = require('./RenderConstants');
/**
* Truncate a number into what could be stored in a 32 bit floating point value.
* @param {number} num Number to truncate.
* @return {number} Truncated value.
*/
const toFloat32 = (function () {
const memory = new Float32Array(1);
return function (num) {
memory[0] = num;
return memory[0];
};
}());
class Skin extends EventEmitter {
/**
* Create a Skin, which stores and/or generates textures for use in rendering.
@ -79,7 +92,11 @@ class Skin extends EventEmitter {
*/
setRotationCenter (x, y) {
const emptySkin = this.size[0] === 0 && this.size[1] === 0;
const changed = x !== this._rotationCenter[0] || y !== this._rotationCenter[1];
// Compare a 32 bit x and y value against the stored 32 bit center
// values.
const changed = (
toFloat32(x) !== this._rotationCenter[0] ||
toFloat32(y) !== this._rotationCenter[1]);
if (!emptySkin && changed) {
this._rotationCenter[0] = x;
this._rotationCenter[1] = y;