Merge pull request #6955 from HaasJona/add/circleSegment

Add path.circleSegment() function

config/changelog.yaml

@@ -2,6 +2,7 @@ Unreleased:
   Added:
     core:
       - The `Path.rotate()` method was added to the core API.
+      - The `Path.circleSegment()` method was added to the core API.
 
   Changed:
     brian:

designs/sandy/src/curved-waistband.mjs

@@ -89,11 +89,11 @@ export function draftCurvedWaistband({
     )
     points.centerNotch = new Path()
       .move(points.ex1Rotated)
-      .curve(points.ex1cFlippedRotated, points.ex2cFlippedRotated, points.ex2FlippedRotated)
+      .circleSegment(-(an + anExtra), points.center)
       .shiftAlong(store.get('waistbandOverlap') / 2)
     points.buttonNotch = new Path()
       .move(points.ex2Rotated)
-      .curve(points.ex2cRotated, points.ex1cRotated, points.ex1Rotated)
+      .circleSegment(an + anExtra, points.center)
       .shiftAlong(store.get('waistbandOverlap'))
     macro('sprinkle', {
       snippet: 'notch',

markdown/dev/reference/api/path/circlesegment/en.md

@@ -0,0 +1,52 @@
+---
+title: Path.circleSegment()
+---
+
+The `Path.circleSegment()` method draws a circle segment
+starting from the current endpoint of the path around the given origin with a given angle.
+
+A positive angle results in a counter-clockwise arc.
+
+A negative angle results in a clockwise arc.
+
+<Tip>
+The new endpoint of this path is the same point
+that 
+```js
+path.end().rotate(deg, origin)
+```
+would return.
+</Tip>
+
+## Signature
+
+```js
+Path path.circleSegment(deg, origin)
+```
+
+<Tip compact>This method is chainable as it returns the `Path` object</Tip>
+
+## Example
+
+<Example caption="Example of the Path.circleSegment() method">
+```js
+({ Point, points, Path, paths, part }) => {
+
+points.from = new Point(10, 20)
+points.origin = new Point(40, 0)
+
+paths.line = new Path()
+.move(points.from)
+.circleSegment(90, points.origin)
+.setText("→ Path.circleSegment() →", "text-sm center fill-note")
+
+paths.helper = new Path()
+.move(paths.line.start())
+.line(points.origin)
+.line(paths.line.end())
+.setClass('dotted stroke-sm')
+
+return part
+}
+```
+</Example>

packages/core/src/path.mjs

@@ -2,6 +2,7 @@ import { Attributes } from './attributes.mjs'
 import { Point } from './point.mjs'
 import { Bezier } from 'bezier-js'
 import {
+  deg2rad,
   linesIntersect,
   lineIntersectsCurve,
   curvesIntersect,
@@ -200,6 +201,43 @@ Path.prototype.bbox = function () {
   return __bbbbox(bbs)
 }
 
+/**
+ * Adds a circle section to this path.
+ * Positive angles create a counter-clockwise arc starting from the current point,
+ * negative angles create a clockwise arc.
+ *
+ * Note: This is unrelated to SVG arc segments in paths, we approximate the circle segment using
+ * standard cubic Bézier curves
+ *
+ * @param {number} deg span of the new circle section in degrees.
+ * @param {Point} origin center point of the circle (rotation origin)
+ * @returns {Path} this
+ */
+Path.prototype.circleSegment = function (deg, origin) {
+  const radius = this.end().dist(origin)
+  // ensure a full circle gets 4 segments for a good approximation
+  // We could use more, but this is not necessary
+  const steps = Math.ceil(Math.abs(deg / 90))
+  const stepAngle = deg / steps
+  const stepAngleRad = deg2rad(stepAngle)
+
+  // magic formula, calculate distance of control points for a good circle segment approximation
+  const distance = radius * (4.0 / 3.0) * Math.tan(stepAngleRad / 4)
+
+  // Append individual segments for arc approximation
+  // steps is usually between 1 and 4
+  for (let i = 0; i < steps; i++) {
+    const startPoint = this.end()
+    const endPoint = startPoint.rotate(stepAngle, origin)
+    const startAngle = startPoint.angle(origin) - 90
+    const endAngle = endPoint.angle(origin) + 90
+    const cp1 = startPoint.shift(startAngle, distance)
+    const cp2 = endPoint.shift(endAngle, distance)
+    this.curve(cp1, cp2, endPoint)
+  }
+  return this
+}
+
 /**
  * Returns this after cleaning out in-place path operations
  *

packages/core/tests/path.test.mjs

@@ -3,6 +3,60 @@ import { round, Path, Point } from '../src/index.mjs'
 import { pathsProxy } from '../src/path.mjs'
 
 describe('Path', () => {
+  describe('circleSegment', () => {
+    it('Should draw a circleSegment', () => {
+      const points = {}
+      points.origin = new Point(10, 20)
+      // radius = 100
+      points.start = points.origin.shift(77, 100)
+
+      const test = new Path().move(points.start).circleSegment(90, points.origin)
+
+      const endPoint = test.end()
+      const expectedEndPoint = points.start.rotate(90, points.origin)
+
+      expect(round(endPoint.x)).to.equal(round(expectedEndPoint.x))
+      expect(round(endPoint.y)).to.equal(round(expectedEndPoint.y))
+      expect(endPoint.sitsOn(expectedEndPoint)).to.equal(true)
+      expect(Math.round(test.length())).to.equal(Math.round(Math.PI * 50))
+    })
+
+    it('Should draw a circleSegment with negative angle', () => {
+      const points = {}
+      points.origin = new Point(10, 20)
+      // radius = 100
+      points.start = points.origin.shift(-122, 100)
+
+      const test = new Path().move(points.start).circleSegment(-45, points.origin)
+
+      const endPoint = test.end()
+      const expectedEndPoint = points.start.rotate(-45, points.origin)
+
+      expect(round(endPoint.x)).to.equal(round(expectedEndPoint.x))
+      expect(round(endPoint.y)).to.equal(round(expectedEndPoint.y))
+      expect(endPoint.sitsOn(expectedEndPoint)).to.equal(true)
+      expect(Math.round(test.length())).to.equal(Math.round(Math.PI * 25))
+    })
+
+    it('Should draw a full circle', () => {
+      const points = {}
+
+      points.origin = new Point(0, 0)
+      // radius = 100
+      points.start = points.origin.shift(0, 100)
+
+      const test = new Path().move(points.start).circleSegment(360, points.origin)
+
+      const endPoint = test.end()
+
+      expect(round(endPoint.x)).to.equal(round(points.start.x))
+      expect(round(endPoint.y)).to.equal(round(points.start.y))
+      expect(endPoint.sitsOn(points.start)).to.equal(true)
+      expect(Math.round(test.length())).to.equal(Math.round(Math.PI * 200))
+      expect(test.ops.length).to.equal(5) // 1 move + 4 cubic curves
+    })
+  })
+
   describe('smurve', () => {
     it('Should draw a smurve', () => {
       const points = {}

plugins/plugin-ringsector/src/index.mjs

@@ -10,35 +10,10 @@ export const getIds = (keys, id) => {
   return ids
 }
 
-/*
- * Helper method to calculate the arc
- */
-const roundExtended = (radius, angle = 90, utils) => {
-  const arg = utils.deg2rad(angle / 2)
-
-  return (radius * 4 * (1 - Math.cos(arg))) / Math.sin(arg) / 3
-}
-
 /*
  * Short IDs
  */
-const keys = [
+const keys = ['center', 'in1', 'in2', 'ex1', 'ex2', 'in2Flipped', 'ex2Flipped']
-  'center',
-  'in1',
-  'in1c',
-  'in2',
-  'in2c',
-  'ex1',
-  'ex1c',
-  'ex2',
-  'ex2c',
-  'in2Flipped',
-  'in2cFlipped',
-  'in1cFlipped',
-  'ex1cFlipped',
-  'ex2cFlipped',
-  'ex2Flipped',
-]
 
 /*
  * The plugin object itself
@@ -52,7 +27,7 @@ export const plugin = {
       for (const id of Object.values(store.get([...storeRoot, 'paths']))) delete paths[id]
       for (const id of Object.values(store.get([...storeRoot, 'points']))) delete points[id]
     },
-    ringsector: function (mc, { utils, Point, points, Path, paths, store }) {
+    ringsector: function (mc, { Point, points, Path, paths, store }) {
       const {
         angle,
         insideRadius,
@@ -68,64 +43,30 @@ export const plugin = {
       const ids = getIds(keys, id)
       const pathIds = getIds(['path'], id)
 
-      /**
-       * Calculates the distance of the control point for the internal
-       * and external arcs using bezierCircleExtended
-       */
-      const distIn = roundExtended(insideRadius, angle / 2, utils)
-      const distEx = roundExtended(outsideRadius, angle / 2, utils)
       // The centre of the circles
       points[ids.center] = center.copy()
 
-      /**
-       * This function is expected to draft ring sectors for
-       * angles up to 180%. Since roundExtended works
-       * best for angles until 90º, we generate the ring
-       * sector using the half angle and then duplicate it
-       */
-
       /**
        * The first point of the internal arc, situated at
        * a insideRadius distance below the centre
        */
       points[ids.in1] = points[ids.center].shift(-90, insideRadius)
 
-      /**
-       * The control point for 'in1'. It's situated at a
-       * distance $distIn calculated with bezierCircleExtended
-       * and the line between it and 'in1' is perpendicular to
-       * the line between 'in1' and the centre, so it's
-       * shifted in the direction 0º
-       */
-      points[ids.in1c] = points[ids.in1].shift(0, distIn)
-
       /**
        * The second point of the internal arc, situated at
        * a $insideRadius distance of the centre in the direction
        * $angle/2 - 90º
        */
       points[ids.in2] = points[ids.center].shift(angle / 2 - 90, insideRadius)
-
-      /**
-       * The control point for 'in2'. It's situated at a
-       * distance $distIn calculated with bezierCircleExtended
-       * and the line between it and 'in2' is perpendicular to
-       * the line between 'in2' and the centre, so it's
-       * shifted in the direction $angle/2 + 180º
-       */
-      points[ids.in2c] = points[ids.in2].shift(angle / 2 + 180, distIn)
-
       /**
        * The points for the external arc are generated in the
        * same way, using $outsideRadius and $distEx instead
        */
       points[ids.ex1] = points[ids.center].shift(-90, outsideRadius)
-      points[ids.ex1c] = points[ids.ex1].shift(0, distEx)
       points[ids.ex2] = points[ids.center].shift(angle / 2 - 90, outsideRadius)
-      points[ids.ex2c] = points[ids.ex2].shift(angle / 2 + 180, distEx)
 
       // Flip all the points to generate the full ring sector
-      for (const id of ['in2', 'in2c', 'in1c', 'ex1c', 'ex2c', 'ex2']) {
+      for (const id of ['in2', 'ex2']) {
         points[ids[id + 'Flipped']] = points[ids[id]].flipX(center)
       }
 
@@ -148,12 +89,9 @@ export const plugin = {
       // Construct the path of the full ring sector
       paths[pathIds.path] = new Path()
         .move(points[ids.ex2Flipped])
-        .curve(points[ids.ex2cFlipped], points[ids.ex1cFlipped], points[ids.ex1])
+        .circleSegment(angle, points[ids.center])
-        .curve(points[ids.ex1c], points[ids.ex2c], points[ids.ex2])
         .line(points[ids.in2])
-        .curve(points[ids.in2c], points[ids.in1c], points[ids.in1])
+        .circleSegment(-angle, points[ids.center])
-        .curve(points[ids.in1cFlipped], points[ids.in2cFlipped], points[ids.in2Flipped])
-        .line(points[ids.ex2Flipped])
         .close()
 
       /*