TrackballControls triggering "change" event unnecessarily

[davidberneda]

(Don't know if its a bug or a feature)

Due to floating point precision, in some cases the following condition is always true:

if ( lastPosition.distanceToSquared( _this.object.position ) > 0 ) {
    _this.dispatchEvent( changeEvent );
   ....

Even when lastPosition and object.position are equal, the resulting distance never gets to absolute zero, is very very small ( ie: 2E-14 ) and the change event never stops.

A fix proposal:

var EPSILON = 0.001;

if ( lastPosition.distanceToSquared( _this.object.position ) > EPSILON ) {

[mrdoob]

Sounds good to me!

[WestLangley]

Just remember that this is a squared distance, so EPSILON should be very small.

[dubejf]

Epsilon added in #4530 by @WestLangley, circa r67 time frame. Closing.