plotboilerplate
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A simple javascript plotting boilerplate for 2d stuff.
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JavaScript
/**
* @author Ikaros Kappler
* @date 2020-12-17
* @modified 2021-01-20 Added UID.
* @modified 2021-02-26 Fixed an error in the svg-arc-calculation (case angle<90deg and anti-clockwise).
* @modified 2024-01-30 Added a missing type in the `describeSVGArc` function.
* @modified 2024-03-01 Added the `getStartPoint` and `getEndPoint` methods.
* @modified 2024-03-08 Added the `containsAngle` method.
* @modified 2024-03-09 Added the `circleSectorIntersection` method to find coherent sector intersections..
* @modified 2024-03-09 Added the `angleAt` method to determine any angle at some ratio.
* @modified 2025-04-02 Adding the `CircleSector.lineIntersections` and `CircleSector.lineIntersectionTangents` and implementing `Intersectable`.
* @modified 2025-04-09 Adding the `CircleSector.move()` method.
* @modified 2025-04-19 Tweaking the `CircleSector.containsAngle` method: all values (input angle, start- and end- angle) are wrapped into [0,2*PI) now.
* @modified 2025-04-19 Class `CircleSector` implements interface `Bounded` now (method `getBounds` added).
* @version 1.2.0
**/
import { Bounds } from "./Bounds";
import { Circle } from "./Circle";
import { Line } from "./Line";
import { UIDGenerator } from "./UIDGenerator";
import { Vertex } from "./Vertex";
import { geomutils } from "./geomutils";
/**
* @classdesc A simple circle sector: circle, start- and end-angle.
*
* @requires Line
* @requires SVGSerializale
* @requires UID
* @requires UIDGenerator
* @requires XYCoords
**/
export class CircleSector {
/**
* Create a new circle sector with given circle, start- and end-angle.
*
* @constructor
* @name CircleSector
* @param {Circle} circle - The circle.
* @param {number} startAngle - The start angle of the sector.
* @param {number} endAngle - The end angle of the sector.
*/
constructor(circle, startAngle, endAngle) {
/**
* Required to generate proper CSS classes and other class related IDs.
**/
this.className = "CircleSector";
this.uid = UIDGenerator.next();
this.circle = circle;
this.startAngle = startAngle;
this.endAngle = endAngle;
}
//--- BEGIN --- Implement interface `IBounded`
/**
* Get the bounds of this ellipse.
*
* The bounds are approximated by the underlying segment buffer; the more segment there are,
* the more accurate will be the returned bounds.
*
* @method getBounds
* @instance
* @memberof VEllipse
* @return {Bounds} The bounds of this curve.
**/
getBounds() {
const _self = this;
const circleBounds = this.circle.getBounds();
// Calculage angles from east, west, north and south box points and check if they are inside
const candidates = [
circleBounds.getNorthPoint(),
circleBounds.getSouthPoint(),
circleBounds.getWestPoint(),
circleBounds.getEastPoint()
].filter((point) => {
// Check for each candidate points if they are contained in this sector. Drop if not.
const angle = new Line(_self.circle.center, point).angle();
return _self.containsAngle(angle);
});
// Compute bounds and inlcude start end end point (they are definitely part of the bounds)
return Bounds.computeFromVertices(candidates.concat([this.getStartPoint(), this.getEndPoint()]));
}
//--- BEGIN --- Implement interface `IBounded`
/**
* Move the circle sector by the given amount.
*
* @method move
* @param {XYCoords} amount - The amount to move.
* @instance
* @memberof CircleSector
* @return {CircleSector} this for chaining
**/
move(amount) {
this.circle.move(amount);
return this;
}
/**
* Checks wether the given angle (must be inside 0 and PI*2) is contained inside this sector.
*
* @param {number} angle - The numeric angle to check.
* @method containsAngle
* @instance
* @memberof CircleSector
* @return {boolean} True if (and only if) this sector contains the given angle.
*/
containsAngle(angle) {
var wrappedAngle = geomutils.mapAngleTo2PI(angle);
var wrappedStart = geomutils.mapAngleTo2PI(this.startAngle);
var wrappedEnd = geomutils.mapAngleTo2PI(this.endAngle);
// TODO: cleanup
// if (this.startAngle <= this.endAngle) {
// return angle >= this.startAngle && angle < this.endAngle;
// } else {
// // startAngle > endAngle
// return angle >= this.startAngle || angle < this.endAngle;
// }
if (wrappedStart <= wrappedEnd) {
return wrappedAngle >= wrappedStart && wrappedAngle < wrappedEnd;
}
else {
// startAngle > endAngle
return wrappedAngle >= wrappedStart || wrappedAngle < wrappedEnd;
}
}
/**
* Get the angle inside this sector for a given ratio. 0.0 means startAngle, and 1.0 means endAngle.
*
* @param {number} t - The ratio inside [0..1].
* @method angleAt
* @instance
* @memberof CircleSector
* @return {number} The angle inside this sector at a given ratio.
*/
angleAt(t) {
if (this.startAngle <= this.endAngle) {
const angleAtRatio = this.startAngle + (this.endAngle - this.startAngle) * t;
return angleAtRatio % (Math.PI * 2.0);
}
else {
// startAngle > endAngle
const angleAtRatio = this.startAngle + (Math.PI * 2 - this.startAngle + this.endAngle) * t;
return angleAtRatio % (Math.PI * 2.0);
}
}
/**
* Get the sectors starting point (on the underlying circle, located at the start angle).
*
* @method getStartPoint
* @instance
* @memberof CircleSector
* @return {Vertex} The sector's stating point.
*/
getStartPoint() {
return this.circle.vertAt(this.startAngle);
}
/**
* Get the sectors ending point (on the underlying circle, located at the end angle).
*
* @method getEndPoint
* @instance
* @memberof CircleSector
* @return {Vertex} The sector's ending point.
*/
getEndPoint() {
return this.circle.vertAt(this.endAngle);
}
/**
* Calculate the intersection of this circle sector and some other sector.
*
* If the two sectors do not corerently intersect (when not both points of the
* radical line are containted in both source sectors) then null is returned.
*
* See demo/53-circle-sector-intersections for a geometric visualisation.
*
* @method circleSectorIntersection
* @instance
* @memberof CircleSector
* @return {CircleSector | null} The intersecion of both sectors or null if they don't intersect.
*/
circleSectorIntersection(sector) {
const radicalLine = this.circle.circleIntersection(sector.circle);
if (!radicalLine) {
// The circles to not intersect at all.
return null;
}
// Circles intersect. Check if this sector interval intersects, too.
const thisIntersectionAngleA = this.circle.center.angle(radicalLine.a);
const thisIntersectionAngleB = this.circle.center.angle(radicalLine.b);
// Is intersection inside this sector?
if (!this.containsAngle(thisIntersectionAngleA) || !this.containsAngle(thisIntersectionAngleB)) {
// At least one circle intersection point is not located in this sector.
// -> no valid intersection at all
return null;
}
// Circles intersect. Check if the passed sector interval intersects, too.
const thatIntersectionAngleA = sector.circle.center.angle(radicalLine.a);
const thatIntersectionAngleB = sector.circle.center.angle(radicalLine.b);
// Is intersection inside this sector?
if (!sector.containsAngle(thatIntersectionAngleA) || !sector.containsAngle(thatIntersectionAngleB)) {
// At least one circle intersection point is not located in this sector.
// -> no valid intersection at all
return null;
}
// The radical line has no direction. Thus the resulting sector _might_ be in reverse order.
// Make a quick logical check: the center of the gap must still be located inside the result sector.
// If not: reverse result.
var gapSector = new CircleSector(this.circle, this.endAngle, this.startAngle);
var centerOfOriginalGap = gapSector.angleAt(0.5);
const resultSector = new CircleSector(new Circle(this.circle.center.clone(), this.circle.radius), thisIntersectionAngleA, thisIntersectionAngleB);
if (resultSector.containsAngle(centerOfOriginalGap)) {
resultSector.startAngle = thisIntersectionAngleB;
resultSector.endAngle = thisIntersectionAngleA;
}
return resultSector;
}
//--- BEGIN --- Implement interface `Intersectable`
/**
* Get the line intersections as vectors with this ellipse.
*
* @method lineIntersections
* @instance
* @param {VertTuple<Vector> ray - The line/ray to intersect this ellipse with.
* @param {boolean} inVectorBoundsOnly - (default=false) Set to true if only intersections within the vector bounds are of interest.
* @returns
*/
lineIntersections(ray, inVectorBoundsOnly = false) {
// First get all line intersections from underlying ellipse.
const ellipseIntersections = this.circle.lineIntersections(ray, inVectorBoundsOnly);
// Drop all intersection points that are not contained in the circle sectors bounds.
const tmpLine = new Line(this.circle.center, new Vertex());
return ellipseIntersections.filter((intersectionPoint) => {
tmpLine.b.set(intersectionPoint);
const lineAngle = tmpLine.angle();
return this.containsAngle(geomutils.wrapMinMax(lineAngle, 0, Math.PI * 2));
});
}
/**
* Get all line intersections of this polygon and their tangents along the shape.
*
* This method returns all intersection tangents (as vectors) with this shape. The returned array of vectors is in no specific order.
*
* @param line
* @param lineIntersectionTangents
* @returns
*/
lineIntersectionTangents(line, inVectorBoundsOnly = false) {
// Find the intersections of all lines plus their tangents inside the circle bounds
const interSectionPoints = this.lineIntersections(line, inVectorBoundsOnly);
return interSectionPoints.map((vert) => {
// Calculate angle
const lineFromCenter = new Line(this.circle.center, vert);
const angle = lineFromCenter.angle();
// console.log("angle", (angle / Math.PI) * 180.0);
// const angle = Math.random() * Math.PI * 2; // TODO
// Calculate tangent at angle
return this.circle.tangentAt(angle);
});
}
//--- END --- Implement interface `Intersectable`
/**
* This function should invalidate any installed listeners and invalidate this object.
* After calling this function the object might not hold valid data any more and
* should not be used.
*
* @method destroy
* @instance
* @memberof CircleSector
* @return {void}
*/
destroy() {
this.circle.destroy();
this.isDestroyed = true;
}
} // END class
CircleSector.circleSectorUtils = {
/**
* Helper function to convert polar circle coordinates to cartesian coordinates.
*
* TODO: generalize for ellipses (two radii).
*
* @param {number} angle - The angle in radians.
*/
polarToCartesian: (centerX, centerY, radius, angle) => {
return {
x: centerX + radius * Math.cos(angle),
y: centerY + radius * Math.sin(angle)
};
},
/**
* Helper function to convert a circle section as SVG arc params (for the `d` attribute).
* Found at: https://stackoverflow.com/questions/5736398/how-to-calculate-the-svg-path-for-an-arc-of-a-circle
*
* TODO: generalize for ellipses (two radii).
*
* @param {boolean} options.moveToStart - If false (default=true) the initial 'Move' command will not be used.
* @return [ 'A', radiusx, radiusy, rotation=0, largeArcFlag=1|0, sweepFlag=0, endx, endy ]
*/
describeSVGArc: (x, y, radius, startAngle, endAngle, options) => {
if (typeof options === "undefined")
options = { moveToStart: true };
const end = CircleSector.circleSectorUtils.polarToCartesian(x, y, radius, endAngle);
const start = CircleSector.circleSectorUtils.polarToCartesian(x, y, radius, startAngle);
// Split full circles into two halves.
// Some browsers have problems to render full circles (described by start==end).
if (Math.PI * 2 - Math.abs(startAngle - endAngle) < 0.001) {
const firstHalf = CircleSector.circleSectorUtils.describeSVGArc(x, y, radius, startAngle, startAngle + (endAngle - startAngle) / 2, options);
const secondHalf = CircleSector.circleSectorUtils.describeSVGArc(x, y, radius, startAngle + (endAngle - startAngle) / 2, endAngle, options);
return firstHalf.concat(secondHalf);
}
// Boolean stored as integers (0|1).
const diff = endAngle - startAngle;
var largeArcFlag;
var sweepFlag;
if (diff < 0) {
largeArcFlag = Math.abs(diff) < Math.PI ? 1 : 0;
sweepFlag = 1;
}
else {
largeArcFlag = Math.abs(diff) > Math.PI ? 1 : 0;
sweepFlag = 1;
}
const pathData = [];
if (options.moveToStart) {
pathData.push("M", start.x, start.y);
}
pathData.push("A", radius, radius, 0, largeArcFlag, sweepFlag, end.x, end.y);
return pathData;
}
};
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