EllipseCurve class
class EllipseCurve extends Curve2D {
num aX, aY;
num xRadius, yRadius;
num aStartAngle, aEndAngle;
bool aClockwise;
EllipseCurve(this.aX, this.aY, this.xRadius, this.yRadius,
this.aStartAngle, this.aEndAngle,
this.aClockwise) : super();
Vector2 getPoint( t ) {
var deltaAngle = aEndAngle - aStartAngle;
if ( !aClockwise ) {
t = 1 - t;
}
var angle = aStartAngle + t * deltaAngle;
var tx = aX + xRadius * Math.cos( angle );
var ty = aY + yRadius * Math.sin( angle );
return new Vector2( tx, ty );
}
}
Extends
Curve<Vector2> > Curve2D > EllipseCurve
Constructors
new EllipseCurve(num aX, num aY, num xRadius, num yRadius, num aStartAngle, num aEndAngle, bool aClockwise) #
Creates a new Object instance.
Object instances have no meaningful state, and are only useful through their identity. An Object instance is equal to itself only.
docs inherited from Object
EllipseCurve(this.aX, this.aY, this.xRadius, this.yRadius,
this.aStartAngle, this.aEndAngle,
this.aClockwise) : super();
Properties
Methods
List getLengths({num divisions: null}) #
inherited from Curve
List getLengths( {num divisions: null} ) {
if (divisions == null) divisions = (_arcLengthDivisions != null) ? (_arcLengthDivisions): 200;
if ( cacheArcLengths != null
&& ( cacheArcLengths.length == divisions + 1 )
&& !needsUpdate) {
//console.log( "cached", this.cacheArcLengths );
return cacheArcLengths;
}
needsUpdate = false;
var cache = [];
var current;
var last = getPoint( 0.0 );
var sum = 0;
cache.add( 0 );
for ( var p = 1; p <= divisions; p ++ ) {
current = getPoint ( p / divisions );
var distance;
// TODO(nelsonsilva) - Must move distanceTo to IVector interface os create a new IHasDistance
if (current is Vector3) {
distance = (current as Vector3).absoluteError( last as Vector3 );
} else {
distance = (current as Vector2).absoluteError( last as Vector2);
}
sum += distance;
cache.add( sum );
last = current;
}
cacheArcLengths = cache;
return cache; // { sums: cache, sum:sum }; Sum is in the last element.
}
Vector2 getNormalVector(t) #
inherited from Curve2D
Vector2 getNormalVector( t ) {
var vec = this.getTangent( t );
return new Vector2( -vec.y , vec.x );
}
Vector2 getPoint(t) #
Vector2 getPoint( t ) {
var deltaAngle = aEndAngle - aStartAngle;
if ( !aClockwise ) {
t = 1 - t;
}
var angle = aStartAngle + t * deltaAngle;
var tx = aX + xRadius * Math.cos( angle );
var ty = aY + yRadius * Math.sin( angle );
return new Vector2( tx, ty );
}
V getPointAt(u) #
inherited from Curve
V getPointAt( u ) {
var t = getUtoTmapping( u );
return getPoint( t );
}
List<V> getPoints([num divisions = null, closedPath = false]) #
inherited from Curve
List<V> getPoints( [num divisions = null, closedPath = false] ) {
if (divisions == null) divisions = 5;
var d, pts = [];
for ( d = 0; d <= divisions; d ++ ) {
pts.add( this.getPoint( d / divisions ) );
}
return pts;
}
List<V> getSpacedPoints([num divisions = 5, closedPath = false]) #
inherited from Curve
List<V> getSpacedPoints( [num divisions = 5, closedPath = false] ) {
var d, pts = [];
for ( d = 0; d <= divisions; d ++ ) {
pts.add( this.getPointAt( d / divisions ) );
}
return pts;
}
V getTangent(t) #
inherited from Curve
V getTangent( t ) {
var delta = 0.0001;
var t1 = t - delta;
var t2 = t + delta;
// Capping in case of danger
if ( t1 < 0 ) t1 = 0;
if ( t2 > 1 ) t2 = 1;
var pt1 = getPoint( t1 );
var pt2 = getPoint( t2 );
var vec = pt2 - pt1;
return vec.normalize();
}
V getTangentAt(u) #
inherited from Curve
V getTangentAt( u ) {
var t = getUtoTmapping( u );
return getTangent( t );
}
List<V> getUPoints([List uList, closedPath = false]) #
inherited from Curve
List<V> getUPoints( [List uList , closedPath = false] ) {
var pts = [];
for ( var u in uList ) {
pts.add( this.getPointAt( u ) );
}
return pts;
}
dynamic getUtoTmapping(u, {distance: null}) #
inherited from Curve
getUtoTmapping( u, {distance: null} ) {
var arcLengths = getLengths();
int i = 0, il = arcLengths.length;
var targetArcLength; // The targeted u distance value to get
if (distance != null) {
targetArcLength = distance;
} else {
targetArcLength = u * arcLengths[ il - 1 ];
}
//var time = Date.now();
// binary search for the index with largest value smaller than target u distance
var low = 0, high = il - 1, comparison;
while ( low <= high ) {
i = ( low + ( high - low ) / 2 ).floor().toInt(); // less likely to overflow, though probably not issue here, JS doesn't really have integers, all numbers are floats
comparison = arcLengths[ i ] - targetArcLength;
if ( comparison < 0 ) {
low = i + 1;
continue;
} else if ( comparison > 0 ) {
high = i - 1;
continue;
} else {
high = i;
break;
// DONE
}
}
i = high;
//console.log('b' , i, low, high, Date.now()- time);
if ( arcLengths[ i ] == targetArcLength ) {
var t = i / ( il - 1 );
return t;
}
// we could get finer grain at lengths, or use simple interpolatation between two points
var lengthBefore = arcLengths[ i ];
var lengthAfter = arcLengths[ i + 1 ];
var segmentLength = lengthAfter - lengthBefore;
// determine where we are between the 'before' and 'after' points
var segmentFraction = ( targetArcLength - lengthBefore ) / segmentLength;
// add that fractional amount to t
var t = ( i + segmentFraction ) / ( il -1 );
return t;
}