Ellipse refactor

Signed-off-by: Mark Tolmacs <mark@lazycat.hu>

packages/excalidraw/charts.ts

@@ -1,5 +1,5 @@
 import type { Radians } from "../math";
-import { point } from "../math";
+import { point, radians } from "../math";
 import {
   COLOR_PALETTE,
   DEFAULT_CHART_COLOR_INDEX,
@@ -205,7 +205,7 @@ const chartXLabels = (
         x: x + index * (BAR_WIDTH + BAR_GAP) + BAR_GAP * 2,
         y: y + BAR_GAP / 2,
         width: BAR_WIDTH,
-        angle: 5.87 as Radians,
+        angle: radians(5.87),
         fontSize: 16,
         textAlign: "center",
         verticalAlign: "top",

packages/excalidraw/data/restore.ts

@@ -55,8 +55,8 @@ import {
   getNormalizedGridStep,
   getNormalizedZoom,
 } from "../scene";
-import type { LocalPoint, Radians } from "../../math";
-import { pointExtent, isFiniteNumber, point } from "../../math";
+import type { LocalPoint } from "../../math";
+import { pointExtent, isFiniteNumber, point, radians } from "../../math";
 
 type RestoredAppState = Omit<
   AppState,
@@ -153,7 +153,7 @@ const restoreElementWithProperties = <
     roughness: element.roughness ?? DEFAULT_ELEMENT_PROPS.roughness,
     opacity:
       element.opacity == null ? DEFAULT_ELEMENT_PROPS.opacity : element.opacity,
-    angle: element.angle || (0 as Radians),
+    angle: element.angle || radians(0),
     x: extra.x ?? element.x ?? 0,
     y: extra.y ?? element.y ?? 0,
     strokeColor: element.strokeColor || DEFAULT_ELEMENT_PROPS.strokeColor,

packages/excalidraw/element/binding.ts

@@ -73,6 +73,7 @@ import {
   pointFromPair,
   pointDistanceSq,
   clamp,
+  radians,
 } from "../../math";
 import { segmentIntersectRectangleElement } from "../../utils/geometry/shape";
 
@@ -845,7 +846,7 @@ export const avoidRectangularCorner = (
     element.x + element.width / 2,
     element.y + element.height / 2,
   );
-  const nonRotatedPoint = pointRotateRads(p, center, -element.angle as Radians);
+  const nonRotatedPoint = pointRotateRads(p, center, radians(-element.angle));
 
   if (nonRotatedPoint[0] < element.x && nonRotatedPoint[1] < element.y) {
     // Top left

packages/math/ellipse.test.ts

@@ -0,0 +1,45 @@
+import { radians } from "./angle";
+import { pointInEllipse, pointOnEllipse } from "./ellipse";
+import { point } from "./point";
+import type { Ellipse, GlobalPoint } from "./types";
+
+describe("point and ellipse", () => {
+  const ellipse: Ellipse<GlobalPoint> = {
+    center: point(0, 0),
+    angle: radians(0),
+    halfWidth: 2,
+    halfHeight: 1,
+  };
+
+  it("point on ellipse", () => {
+    [point(0, 1), point(0, -1), point(2, 0), point(-2, 0)].forEach((p) => {
+      expect(pointOnEllipse(p, ellipse)).toBe(true);
+    });
+    expect(pointOnEllipse(point(-1.4, 0.7), ellipse, 0.1)).toBe(true);
+    expect(pointOnEllipse(point(-1.4, 0.71), ellipse, 0.01)).toBe(true);
+
+    expect(pointOnEllipse(point(1.4, 0.7), ellipse, 0.1)).toBe(true);
+    expect(pointOnEllipse(point(1.4, 0.71), ellipse, 0.01)).toBe(true);
+
+    expect(pointOnEllipse(point(1, -0.86), ellipse, 0.1)).toBe(true);
+    expect(pointOnEllipse(point(1, -0.86), ellipse, 0.01)).toBe(true);
+
+    expect(pointOnEllipse(point(-1, -0.86), ellipse, 0.1)).toBe(true);
+    expect(pointOnEllipse(point(-1, -0.86), ellipse, 0.01)).toBe(true);
+
+    expect(pointOnEllipse(point(-1, 0.8), ellipse)).toBe(false);
+    expect(pointOnEllipse(point(1, -0.8), ellipse)).toBe(false);
+  });
+
+  it("point in ellipse", () => {
+    [point(0, 1), point(0, -1), point(2, 0), point(-2, 0)].forEach((p) => {
+      expect(pointInEllipse(p, ellipse)).toBe(true);
+    });
+
+    expect(pointInEllipse(point(-1, 0.8), ellipse)).toBe(true);
+    expect(pointInEllipse(point(1, -0.8), ellipse)).toBe(true);
+
+    expect(pointInEllipse(point(-1, 1), ellipse)).toBe(false);
+    expect(pointInEllipse(point(-1.4, 0.8), ellipse)).toBe(false);
+  });
+});

packages/math/ellipse.ts

@@ -0,0 +1,231 @@
+import { radians } from "./angle";
+import { line } from "./line";
+import {
+  point,
+  pointDistance,
+  pointFromVector,
+  pointRotateRads,
+} from "./point";
+import type { Ellipse, GenericPoint, Line } from "./types";
+import { PRECISION } from "./utils";
+import {
+  vector,
+  vectorAdd,
+  vectorDot,
+  vectorFromPoint,
+  vectorScale,
+} from "./vector";
+
+export const pointInEllipse = <Point extends GenericPoint>(
+  p: Point,
+  ellipse: Ellipse<Point>,
+) => {
+  const { center, angle, halfWidth, halfHeight } = ellipse;
+  const translatedPoint = vectorAdd(
+    vectorFromPoint(p),
+    vectorScale(vectorFromPoint(center), -1),
+  );
+  const [rotatedPointX, rotatedPointY] = pointRotateRads(
+    pointFromVector(translatedPoint),
+    point(0, 0),
+    radians(-angle),
+  );
+
+  return (
+    (rotatedPointX / halfWidth) * (rotatedPointX / halfWidth) +
+      (rotatedPointY / halfHeight) * (rotatedPointY / halfHeight) <=
+    1
+  );
+};
+
+export const pointOnEllipse = <Point extends GenericPoint>(
+  point: Point,
+  ellipse: Ellipse<Point>,
+  threshold = PRECISION,
+) => {
+  return distanceToEllipse(point, ellipse) <= threshold;
+};
+
+export const ellipseAxes = <Point extends GenericPoint>(
+  ellipse: Ellipse<Point>,
+) => {
+  const widthGreaterThanHeight = ellipse.halfWidth > ellipse.halfHeight;
+
+  const majorAxis = widthGreaterThanHeight
+    ? ellipse.halfWidth * 2
+    : ellipse.halfHeight * 2;
+  const minorAxis = widthGreaterThanHeight
+    ? ellipse.halfHeight * 2
+    : ellipse.halfWidth * 2;
+
+  return {
+    majorAxis,
+    minorAxis,
+  };
+};
+
+export const ellipseFocusToCenter = <Point extends GenericPoint>(
+  ellipse: Ellipse<Point>,
+) => {
+  const { majorAxis, minorAxis } = ellipseAxes(ellipse);
+
+  return Math.sqrt(majorAxis ** 2 - minorAxis ** 2);
+};
+
+export const ellipseExtremes = <Point extends GenericPoint>(
+  ellipse: Ellipse<Point>,
+) => {
+  const { center, angle } = ellipse;
+  const { majorAxis, minorAxis } = ellipseAxes(ellipse);
+
+  const cos = Math.cos(angle);
+  const sin = Math.sin(angle);
+
+  const sqSum = majorAxis ** 2 + minorAxis ** 2;
+  const sqDiff = (majorAxis ** 2 - minorAxis ** 2) * Math.cos(2 * angle);
+
+  const yMax = Math.sqrt((sqSum - sqDiff) / 2);
+  const xAtYMax =
+    (yMax * sqSum * sin * cos) /
+    (majorAxis ** 2 * sin ** 2 + minorAxis ** 2 * cos ** 2);
+
+  const xMax = Math.sqrt((sqSum + sqDiff) / 2);
+  const yAtXMax =
+    (xMax * sqSum * sin * cos) /
+    (majorAxis ** 2 * cos ** 2 + minorAxis ** 2 * sin ** 2);
+  const centerVector = vectorFromPoint(center);
+
+  return [
+    vectorAdd(vector(xAtYMax, yMax), centerVector),
+    vectorAdd(vectorScale(vector(xAtYMax, yMax), -1), centerVector),
+    vectorAdd(vector(xMax, yAtXMax), centerVector),
+    vectorAdd(vector(xMax, yAtXMax), centerVector),
+  ];
+};
+
+const distanceToEllipse = <Point extends GenericPoint>(
+  p: Point,
+  ellipse: Ellipse<Point>,
+) => {
+  const { angle, halfWidth, halfHeight, center } = ellipse;
+  const a = halfWidth;
+  const b = halfHeight;
+  const translatedPoint = vectorAdd(
+    vectorFromPoint(p),
+    vectorScale(vectorFromPoint(center), -1),
+  );
+  const [rotatedPointX, rotatedPointY] = pointRotateRads(
+    pointFromVector(translatedPoint),
+    point(0, 0),
+    radians(-angle),
+  );
+
+  const px = Math.abs(rotatedPointX);
+  const py = Math.abs(rotatedPointY);
+
+  let tx = 0.707;
+  let ty = 0.707;
+
+  for (let i = 0; i < 3; i++) {
+    const x = a * tx;
+    const y = b * ty;
+
+    const ex = ((a * a - b * b) * tx ** 3) / a;
+    const ey = ((b * b - a * a) * ty ** 3) / b;
+
+    const rx = x - ex;
+    const ry = y - ey;
+
+    const qx = px - ex;
+    const qy = py - ey;
+
+    const r = Math.hypot(ry, rx);
+    const q = Math.hypot(qy, qx);
+
+    tx = Math.min(1, Math.max(0, ((qx * r) / q + ex) / a));
+    ty = Math.min(1, Math.max(0, ((qy * r) / q + ey) / b));
+    const t = Math.hypot(ty, tx);
+    tx /= t;
+    ty /= t;
+  }
+
+  const [minX, minY] = [
+    a * tx * Math.sign(rotatedPointX),
+    b * ty * Math.sign(rotatedPointY),
+  ];
+
+  return pointDistance(point(rotatedPointX, rotatedPointY), point(minX, minY));
+};
+
+/**
+ * Calculate a maximum of two intercept points for a line going throug an
+ * ellipse.
+ */
+export function interceptPointsOfLineAndEllipse<Point extends GenericPoint>(
+  ellipse: Readonly<Ellipse<Point>>,
+  l: Readonly<Line<Point>>,
+): Point[] {
+  const rx = ellipse.halfWidth;
+  const ry = ellipse.halfHeight;
+  const nonRotatedLine = line(
+    pointRotateRads(l[0], ellipse.center, radians(-ellipse.angle)),
+    pointRotateRads(l[1], ellipse.center, radians(-ellipse.angle)),
+  );
+  const dir = vectorFromPoint(nonRotatedLine[1], nonRotatedLine[0]);
+  const diff = vector(
+    nonRotatedLine[0][0] - ellipse.center[0],
+    nonRotatedLine[0][1] - ellipse.center[1],
+  );
+  const mDir = vector(dir[0] / (rx * rx), dir[1] / (ry * ry));
+  const mDiff = vector(diff[0] / (rx * rx), diff[1] / (ry * ry));
+
+  const a = vectorDot(dir, mDir);
+  const b = vectorDot(dir, mDiff);
+  const c = vectorDot(diff, mDiff) - 1.0;
+  const d = b * b - a * c;
+
+  const intersections: Point[] = [];
+
+  if (d > 0) {
+    const t_a = (-b - Math.sqrt(d)) / a;
+    const t_b = (-b + Math.sqrt(d)) / a;
+
+    if (0 <= t_a && t_a <= 1) {
+      intersections.push(
+        point(
+          nonRotatedLine[0][0] +
+            (nonRotatedLine[1][0] - nonRotatedLine[0][0]) * t_a,
+          nonRotatedLine[0][1] +
+            (nonRotatedLine[1][1] - nonRotatedLine[0][1]) * t_a,
+        ),
+      );
+    }
+
+    if (0 <= t_b && t_b <= 1) {
+      intersections.push(
+        point(
+          nonRotatedLine[0][0] +
+            (nonRotatedLine[1][0] - nonRotatedLine[0][0]) * t_b,
+          nonRotatedLine[0][1] +
+            (nonRotatedLine[1][1] - nonRotatedLine[0][1]) * t_b,
+        ),
+      );
+    }
+  } else if (d === 0) {
+    const t = -b / a;
+    if (0 <= t && t <= 1) {
+      intersections.push(
+        point(
+          nonRotatedLine[0][0] +
+            (nonRotatedLine[1][0] - nonRotatedLine[0][0]) * t,
+          nonRotatedLine[0][1] +
+            (nonRotatedLine[1][1] - nonRotatedLine[0][1]) * t,
+        ),
+      );
+    }
+  }
+
+  return intersections.map((point) =>
+    pointRotateRads(point, ellipse.center, ellipse.angle),
+  );
+}

packages/math/index.ts

@@ -1,6 +1,7 @@
 export * from "./arc";
 export * from "./angle";
 export * from "./curve";
+export * from "./ellipse";
 export * from "./line";
 export * from "./path";
 export * from "./point";

packages/math/types.ts

@@ -143,3 +143,13 @@ export type Extent = {
 } & {
   _brand: "excalimath_extent";
 };
+
+// an ellipse is specified by its center, angle, and its major and minor axes
+// but for the sake of simplicity, we've used halfWidth and halfHeight instead
+// in replace of semi major and semi minor axes
+export type Ellipse<Point extends GenericPoint> = {
+  center: Point;
+  angle: Radians;
+  halfWidth: number;
+  halfHeight: number;
+};

packages/utils/collision.ts

@@ -1,9 +1,5 @@
 import type { Polycurve, Polyline } from "./geometry/shape";
-import {
-  pointInEllipse,
-  pointOnEllipse,
-  type GeometricShape,
-} from "./geometry/shape";
+import { type GeometricShape } from "./geometry/shape";
 import type { Curve, ViewportPoint } from "../math";
 import {
   lineSegment,
@@ -15,6 +11,8 @@ import {
   type GlobalPoint,
   type LocalPoint,
   type Polygon,
+  pointOnEllipse,
+  pointInEllipse,
 } from "../math";
 
 // check if the given point is considered on the given shape's border

packages/utils/geometry/geometry.test.ts

@@ -1,4 +1,4 @@
-import type { GlobalPoint, LineSegment, Polygon, Radians } from "../../math";
+import type { GlobalPoint, LineSegment, Polygon } from "../../math";
 import {
   point,
   lineSegment,
@@ -7,7 +7,6 @@ import {
   pointOnPolygon,
   polygonIncludesPoint,
 } from "../../math";
-import { pointInEllipse, pointOnEllipse, type Ellipse } from "./shape";
 
 describe("point and line", () => {
   const s: LineSegment<GlobalPoint> = lineSegment(point(1, 0), point(1, 2));
@@ -47,44 +46,3 @@ describe("point and polygon", () => {
     expect(polygonIncludesPoint(point(3, 3), poly)).toBe(false);
   });
 });
-
-describe("point and ellipse", () => {
-  const ellipse: Ellipse<GlobalPoint> = {
-    center: point(0, 0),
-    angle: 0 as Radians,
-    halfWidth: 2,
-    halfHeight: 1,
-  };
-
-  it("point on ellipse", () => {
-    [point(0, 1), point(0, -1), point(2, 0), point(-2, 0)].forEach((p) => {
-      expect(pointOnEllipse(p, ellipse)).toBe(true);
-    });
-    expect(pointOnEllipse(point(-1.4, 0.7), ellipse, 0.1)).toBe(true);
-    expect(pointOnEllipse(point(-1.4, 0.71), ellipse, 0.01)).toBe(true);
-
-    expect(pointOnEllipse(point(1.4, 0.7), ellipse, 0.1)).toBe(true);
-    expect(pointOnEllipse(point(1.4, 0.71), ellipse, 0.01)).toBe(true);
-
-    expect(pointOnEllipse(point(1, -0.86), ellipse, 0.1)).toBe(true);
-    expect(pointOnEllipse(point(1, -0.86), ellipse, 0.01)).toBe(true);
-
-    expect(pointOnEllipse(point(-1, -0.86), ellipse, 0.1)).toBe(true);
-    expect(pointOnEllipse(point(-1, -0.86), ellipse, 0.01)).toBe(true);
-
-    expect(pointOnEllipse(point(-1, 0.8), ellipse)).toBe(false);
-    expect(pointOnEllipse(point(1, -0.8), ellipse)).toBe(false);
-  });
-
-  it("point in ellipse", () => {
-    [point(0, 1), point(0, -1), point(2, 0), point(-2, 0)].forEach((p) => {
-      expect(pointInEllipse(p, ellipse)).toBe(true);
-    });
-
-    expect(pointInEllipse(point(-1, 0.8), ellipse)).toBe(true);
-    expect(pointInEllipse(point(1, -0.8), ellipse)).toBe(true);
-
-    expect(pointInEllipse(point(-1, 1), ellipse)).toBe(false);
-    expect(pointInEllipse(point(-1.4, 0.8), ellipse)).toBe(false);
-  });
-});

packages/utils/geometry/shape.ts

@@ -14,6 +14,8 @@
 
 import type {
   Curve,
+  Ellipse,
+  GenericPoint,
   LineSegment,
   Polygon,
   Radians,
@@ -23,18 +25,15 @@ import {
   curve,
   lineSegment,
   point,
-  pointDistance,
   pointFromArray,
   pointFromVector,
   pointRotateRads,
   polygon,
   polygonFromPoints,
-  PRECISION,
   segmentsIntersectAt,
   vector,
   vectorAdd,
   vectorFromPoint,
-  vectorScale,
   type GlobalPoint,
   type LocalPoint,
 } from "../../math";
@@ -70,19 +69,7 @@ export type Polyline<Point extends GlobalPoint | LocalPoint | ViewportPoint> =
 export type Polycurve<Point extends GlobalPoint | LocalPoint | ViewportPoint> =
   Curve<Point>[];
 
-// an ellipse is specified by its center, angle, and its major and minor axes
-// but for the sake of simplicity, we've used halfWidth and halfHeight instead
-// in replace of semi major and semi minor axes
-export type Ellipse<Point extends GlobalPoint | LocalPoint | ViewportPoint> = {
-  center: Point;
-  angle: Radians;
-  halfWidth: number;
-  halfHeight: number;
-};
-
-export type GeometricShape<
-  Point extends GlobalPoint | LocalPoint | ViewportPoint,
-> =
+export type GeometricShape<Point extends GenericPoint> =
   | {
       type: "line";
       data: LineSegment<Point>;
@@ -403,150 +390,3 @@ export const segmentIntersectRectangleElement = <
     .map((s) => segmentsIntersectAt(segment, s))
     .filter((i): i is Point => !!i);
 };
-
-const distanceToEllipse = <
-  Point extends LocalPoint | GlobalPoint | ViewportPoint,
->(
-  p: Point,
-  ellipse: Ellipse<Point>,
-) => {
-  const { angle, halfWidth, halfHeight, center } = ellipse;
-  const a = halfWidth;
-  const b = halfHeight;
-  const translatedPoint = vectorAdd(
-    vectorFromPoint(p),
-    vectorScale(vectorFromPoint(center), -1),
-  );
-  const [rotatedPointX, rotatedPointY] = pointRotateRads(
-    pointFromVector(translatedPoint),
-    point(0, 0),
-    -angle as Radians,
-  );
-
-  const px = Math.abs(rotatedPointX);
-  const py = Math.abs(rotatedPointY);
-
-  let tx = 0.707;
-  let ty = 0.707;
-
-  for (let i = 0; i < 3; i++) {
-    const x = a * tx;
-    const y = b * ty;
-
-    const ex = ((a * a - b * b) * tx ** 3) / a;
-    const ey = ((b * b - a * a) * ty ** 3) / b;
-
-    const rx = x - ex;
-    const ry = y - ey;
-
-    const qx = px - ex;
-    const qy = py - ey;
-
-    const r = Math.hypot(ry, rx);
-    const q = Math.hypot(qy, qx);
-
-    tx = Math.min(1, Math.max(0, ((qx * r) / q + ex) / a));
-    ty = Math.min(1, Math.max(0, ((qy * r) / q + ey) / b));
-    const t = Math.hypot(ty, tx);
-    tx /= t;
-    ty /= t;
-  }
-
-  const [minX, minY] = [
-    a * tx * Math.sign(rotatedPointX),
-    b * ty * Math.sign(rotatedPointY),
-  ];
-
-  return pointDistance(point(rotatedPointX, rotatedPointY), point(minX, minY));
-};
-
-export const pointOnEllipse = <
-  Point extends LocalPoint | GlobalPoint | ViewportPoint,
->(
-  point: Point,
-  ellipse: Ellipse<Point>,
-  threshold = PRECISION,
-) => {
-  return distanceToEllipse(point, ellipse) <= threshold;
-};
-
-export const pointInEllipse = <
-  Point extends LocalPoint | GlobalPoint | ViewportPoint,
->(
-  p: Point,
-  ellipse: Ellipse<Point>,
-) => {
-  const { center, angle, halfWidth, halfHeight } = ellipse;
-  const translatedPoint = vectorAdd(
-    vectorFromPoint(p),
-    vectorScale(vectorFromPoint(center), -1),
-  );
-  const [rotatedPointX, rotatedPointY] = pointRotateRads(
-    pointFromVector(translatedPoint),
-    point(0, 0),
-    -angle as Radians,
-  );
-
-  return (
-    (rotatedPointX / halfWidth) * (rotatedPointX / halfWidth) +
-      (rotatedPointY / halfHeight) * (rotatedPointY / halfHeight) <=
-    1
-  );
-};
-
-export const ellipseAxes = <Point extends LocalPoint | GlobalPoint>(
-  ellipse: Ellipse<Point>,
-) => {
-  const widthGreaterThanHeight = ellipse.halfWidth > ellipse.halfHeight;
-
-  const majorAxis = widthGreaterThanHeight
-    ? ellipse.halfWidth * 2
-    : ellipse.halfHeight * 2;
-  const minorAxis = widthGreaterThanHeight
-    ? ellipse.halfHeight * 2
-    : ellipse.halfWidth * 2;
-
-  return {
-    majorAxis,
-    minorAxis,
-  };
-};
-
-export const ellipseFocusToCenter = <Point extends LocalPoint | GlobalPoint>(
-  ellipse: Ellipse<Point>,
-) => {
-  const { majorAxis, minorAxis } = ellipseAxes(ellipse);
-
-  return Math.sqrt(majorAxis ** 2 - minorAxis ** 2);
-};
-
-export const ellipseExtremes = <Point extends LocalPoint | GlobalPoint>(
-  ellipse: Ellipse<Point>,
-) => {
-  const { center, angle } = ellipse;
-  const { majorAxis, minorAxis } = ellipseAxes(ellipse);
-
-  const cos = Math.cos(angle);
-  const sin = Math.sin(angle);
-
-  const sqSum = majorAxis ** 2 + minorAxis ** 2;
-  const sqDiff = (majorAxis ** 2 - minorAxis ** 2) * Math.cos(2 * angle);
-
-  const yMax = Math.sqrt((sqSum - sqDiff) / 2);
-  const xAtYMax =
-    (yMax * sqSum * sin * cos) /
-    (majorAxis ** 2 * sin ** 2 + minorAxis ** 2 * cos ** 2);
-
-  const xMax = Math.sqrt((sqSum + sqDiff) / 2);
-  const yAtXMax =
-    (xMax * sqSum * sin * cos) /
-    (majorAxis ** 2 * cos ** 2 + minorAxis ** 2 * sin ** 2);
-  const centerVector = vectorFromPoint(center);
-
-  return [
-    vectorAdd(vector(xAtYMax, yMax), centerVector),
-    vectorAdd(vectorScale(vector(xAtYMax, yMax), -1), centerVector),
-    vectorAdd(vector(xMax, yAtXMax), centerVector),
-    vectorAdd(vector(xMax, yAtXMax), centerVector),
-  ];
-};