feat(geom): re-add arcLength() impls, update imports

packages/geom2/src/api.ts

@@ -7,6 +7,7 @@ import {
 import {
     DEFAULT,
     defmulti,
+    MultiFn1,
     MultiFn1O,
     MultiFn2O
 } from "@thi.ng/defmulti";
@@ -16,14 +17,14 @@ import { ReadonlyMat } from "@thi.ng/matrices/api";
 import { add } from "@thi.ng/vectors3/add";
 import { ReadonlyVec, Vec } from "@thi.ng/vectors3/api";
 import { copy } from "@thi.ng/vectors3/copy";
+import { max } from "@thi.ng/vectors3/max";
+import { min } from "@thi.ng/vectors3/min";
 import { mixN } from "@thi.ng/vectors3/mixn";
 import { mul } from "@thi.ng/vectors3/mul";
-import { min } from "@thi.ng/vectors3/min";
-import { max } from "@thi.ng/vectors3/max";
 import { neg } from "@thi.ng/vectors3/neg";
-import { sub } from "@thi.ng/vectors3/sub";
 import { perpendicularLeft2 } from "@thi.ng/vectors3/perpendicular";
 import { rotateZ } from "@thi.ng/vectors3/rotate";
+import { sub } from "@thi.ng/vectors3/sub";
 import { subdivKernel3 } from "./internal/subdiv-curve";
 import { warpPoints } from "./internal/warp";
 
@@ -209,6 +210,8 @@ export type VecPair = [Vec, Vec];
 
 const dispatch = (x: IShape) => x.type;
 
+export const arcLength: MultiFn1<IShape, number> = defmulti(dispatch);
+
 export const area: MultiFn1O<IShape, boolean, number> = defmulti(dispatch);
 area.add(DEFAULT, () => 0);
 

packages/geom2/src/circle.ts

@@ -13,27 +13,28 @@ import { mulN2 } from "@thi.ng/vectors3/muln";
 import { normalize } from "@thi.ng/vectors3/normalize";
 import { sub2 } from "@thi.ng/vectors3/sub";
 import { subN2 } from "@thi.ng/vectors3/subn";
-import { circumCenter } from "./internal/circumcenter";
-import "./polygon";
 import {
-    perimeter,
+    arcLength,
     area,
+    Attribs,
     bounds,
+    center,
     centroid,
     Circle2,
-    Type,
-    Attribs,
-    Rect2,
-    vertices,
+    classifyPoint,
+    closestPoint,
     DEFAULT_SAMPLES,
+    perimeter,
     pointAt,
     pointInside,
-    classifyPoint,
-    closestPoint,
-    translate,
-    center,
+    Rect2,
     SamplingOpts,
+    translate,
+    Type,
+    vertices
 } from "./api";
+import { circumCenter } from "./internal/circumcenter";
+import "./polygon";
 
 export function circle(pos: Vec, r = 1, attribs?: Attribs): Circle2 {
     return new Circle2(pos, r, attribs);
@@ -56,8 +57,13 @@ implementations(
 
     null,
 
+    arcLength,
+    (circle: Circle2) =>
+        TAU * circle.r,
+
     area,
-    (circle: Circle2) => PI * circle.r * circle.r,
+    (circle: Circle2) =>
+        PI * circle.r * circle.r,
 
     bounds,
     (circle: Circle2) =>

packages/geom2/src/ellipse.ts

@@ -8,25 +8,26 @@ import { copy } from "@thi.ng/vectors3/copy";
 import { madd2 } from "@thi.ng/vectors3/madd";
 import { mulN2 } from "@thi.ng/vectors3/muln";
 import { sub2 } from "@thi.ng/vectors3/sub";
-import "./polygon";
 import {
-    perimeter,
+    arcLength,
     area,
+    asPolygon,
+    Attribs,
     bounds,
+    center,
     centroid,
-    Ellipse2,
-    Type,
-    Attribs,
-    Rect2,
-    vertices,
-    Polygon2,
-    asPolygon,
     DEFAULT_SAMPLES,
+    Ellipse2,
+    perimeter,
     pointAt,
-    center,
-    translate,
+    Polygon2,
+    Rect2,
     SamplingOpts,
+    translate,
+    Type,
+    vertices
 } from "./api";
+import "./polygon";
 
 export function ellipse(pos: Vec, r = [1, 1], attribs?: Attribs): Ellipse2 {
     return new Ellipse2(pos, r, attribs);
@@ -37,8 +38,17 @@ implementations(
 
     null,
 
+    arcLength,
+    (ellipse: Ellipse2) => {
+        const [a, b] = ellipse.r;
+        // Ramanujan approximation
+        // https://www.mathsisfun.com/geometry/ellipse-perimeter.html
+        return PI * ((3 * (a + b)) - Math.sqrt((3 * a + b) * (3 * b + a)));
+    },
+
     area,
-    (ellipse: Ellipse2) => PI * ellipse.r[0] * ellipse.r[1],
+    (ellipse: Ellipse2) =>
+        PI * ellipse.r[0] * ellipse.r[1],
 
     asPolygon,
     (ellipse: Ellipse2, opts) =>

packages/geom2/src/internal/arc-length.ts

@@ -0,0 +1,15 @@
+import { ReadonlyVec } from "@thi.ng/vectors3/api";
+import { dist } from "@thi.ng/vectors3/dist";
+
+export const arcLength = (pts: ReadonlyVec[], closed = false) => {
+    const num = pts.length;
+    if (num < 2) return 0;
+    let res = 0;
+    let p = pts[0];
+    let q = pts[1];
+    for (let i = 1; i < num; i++ , p = q, q = pts[i]) {
+        res += dist(p, q);
+    }
+    closed && (res += dist(p, pts[0]));
+    return res;
+};

packages/geom2/src/line.ts

@@ -4,12 +4,8 @@ import { ReadonlyVec, Vec } from "@thi.ng/vectors3/api";
 import { dist } from "@thi.ng/vectors3/dist";
 import { mixN } from "@thi.ng/vectors3/mixn";
 import { sub } from "@thi.ng/vectors3/sub";
-import { direction } from "./internal/direction";
-import { intersectLines2 } from "./internal/line-intersection";
-import { offsetLine } from "./internal/offset";
-import { transformPoints } from "./internal/transform";
-import "./polygon";
 import {
+    arcLength,
     asCubic,
     asPolyline,
     Attribs,
@@ -24,13 +20,18 @@ import {
     Polygon2,
     Polyline2,
     Rect2,
+    resample,
     tangentAt,
     transform,
     Type,
     VecPair,
-    vertices,
-    resample,
+    vertices
 } from "./api";
+import { direction } from "./internal/direction";
+import { intersectLines2 } from "./internal/line-intersection";
+import { offsetLine } from "./internal/offset";
+import { transformPoints } from "./internal/transform";
+import "./polygon";
 
 export function line(a: Vec, b: Vec, attribs?: Attribs) {
     return new Line2([a, b], attribs);
@@ -52,6 +53,10 @@ implementations(
         ],
     },
 
+    arcLength,
+    (line: Line2) =>
+        dist(line.a, line.b),
+
     asCubic,
     (line: Line2) =>
         [Cubic2.fromLine(line.a, line.b, { ...line.attribs })],

packages/geom2/src/polygon.ts

@@ -16,20 +16,10 @@ import { add2 } from "@thi.ng/vectors3/add";
 import { ReadonlyVec, Vec } from "@thi.ng/vectors3/api";
 import { cartesian2 } from "@thi.ng/vectors3/cartesian";
 import { signedArea2 } from "@thi.ng/vectors3/signed-area";
-import "./container2";
-import { centerOfWeight2 } from "./internal/centroid";
-import { edges as _edges } from "./internal/edges";
-import { booleanOp } from "./internal/greiner-hormann";
-import { offset as _offset } from "./internal/offset";
-import { perimeter as _perimeter } from "./internal/perimeter";
-import { pointInside as _pointInside, polygonArea } from "./internal/polygon";
-import { Sampler } from "./internal/sampler";
-import { subdivideCurve } from "./internal/subdiv-curve";
-import { sutherlandHodgeman } from "./internal/sutherland-hodgeman";
-import { transformPoints } from "./internal/transform";
-import { tessellatePoints } from "./tessellate";
 import {
+    arcLength,
     area,
+    asPolygon,
     Attribs,
     bounds,
     centroid,
@@ -59,10 +49,22 @@ import {
     translate,
     Type,
     union,
-    vertices,
-    asPolygon,
+    vertices
 } from "./api";
+import "./container2";
+import { centerOfWeight2 } from "./internal/centroid";
+import { edges as _edges } from "./internal/edges";
+import { booleanOp } from "./internal/greiner-hormann";
+import { offset as _offset } from "./internal/offset";
+import { perimeter as _perimeter } from "./internal/perimeter";
+import { pointInside as _pointInside, polygonArea } from "./internal/polygon";
+import { Sampler } from "./internal/sampler";
+import { subdivideCurve } from "./internal/subdiv-curve";
+import { sutherlandHodgeman } from "./internal/sutherland-hodgeman";
+import { transformPoints } from "./internal/transform";
+import { tessellatePoints } from "./tessellate";
 import { douglasPeucker2 } from "./internal/douglas–peucker";
+import { arcLength as _arcLength } from "./internal/arc-length";
 
 export function polygon(points: Vec[], attribs?: Attribs): Polygon2 {
     return new Polygon2(points, attribs);
@@ -118,6 +120,10 @@ implementations(
         ]
     },
 
+    arcLength,
+    (poly: Polygon2) =>
+        _arcLength(poly.points, true),
+
     area,
     (poly: Polygon2, signed = true) => {
         const area = polygonArea(poly.points);

packages/geom2/src/polyline.ts

@@ -5,6 +5,7 @@ import { map } from "@thi.ng/transducers/xform/map";
 import { add2 } from "@thi.ng/vectors3/add";
 import { ReadonlyVec, Vec } from "@thi.ng/vectors3/api";
 import {
+    arcLength,
     asCubic,
     Attribs,
     bounds,
@@ -30,6 +31,7 @@ import {
     vertices
 } from "./api";
 import "./container2";
+import { arcLength as _arcLength } from "./internal/arc-length";
 import { centroid as _centroid } from "./internal/centroid";
 import { edges as _edges } from "./internal/edges";
 import { offset as _offset } from "./internal/offset";
@@ -55,6 +57,10 @@ implementations(
         ],
     },
 
+    arcLength,
+    (poly: Polygon2) =>
+        _arcLength(poly.points),
+
     asCubic,
     (line: Polyline2) =>
         map((e) => Cubic2.fromLine(...e), _edges(line.points)),

packages/geom2/src/quad.ts

@@ -4,6 +4,7 @@ import { add2 } from "@thi.ng/vectors3/add";
 import { ReadonlyVec, Vec } from "@thi.ng/vectors3/api";
 import { mixBilinear2 } from "@thi.ng/vectors3/mix-bilinear";
 import {
+    arcLength,
     area,
     Attribs,
     bounds,
@@ -39,6 +40,7 @@ implementations(
             flip,
         ],
         [Type.POLYGON2]: [
+            arcLength,
             area,
             centroid,
             clipConvex,

packages/geom2/src/rect.ts

@@ -7,40 +7,41 @@ import { div2 } from "@thi.ng/vectors3/div";
 import { madd2 } from "@thi.ng/vectors3/madd";
 import { maddN2 } from "@thi.ng/vectors3/maddn";
 import { sub } from "@thi.ng/vectors3/sub";
-import { unionBounds } from "./internal/bounds";
-import { edges as _edges } from "./internal/edges";
-import { booleanOp } from "./internal/greiner-hormann";
-import { Sampler } from "./internal/sampler";
-import { sutherlandHodgeman } from "./internal/sutherland-hodgeman";
-import { transformPoints } from "./internal/transform";
-import "./polygon";
-import { tessellatePoints } from "./tessellate";
 import {
+    arcLength,
     area,
     Attribs,
     bounds,
     centroid,
     clipConvex,
     ClipMode,
+    edges,
     IShape,
     mapPoint,
     perimeter,
+    pointAt,
+    pointInside,
     Polygon2,
     Rect2,
+    resample,
+    SamplingOpts,
     tessellate,
     Tessellator,
+    transform,
+    translate,
     Type,
     union,
     unmapPoint,
-    vertices,
-    transform,
-    SamplingOpts,
-    edges,
-    translate,
-    resample,
-    pointAt,
-    pointInside,
+    vertices
 } from "./api";
+import { unionBounds } from "./internal/bounds";
+import { edges as _edges } from "./internal/edges";
+import { booleanOp } from "./internal/greiner-hormann";
+import { Sampler } from "./internal/sampler";
+import { sutherlandHodgeman } from "./internal/sutherland-hodgeman";
+import { transformPoints } from "./internal/transform";
+import "./polygon";
+import { tessellatePoints } from "./tessellate";
 
 export function rect(pos: Vec, size: Vec, attribs?: Attribs) {
     return new Rect2(pos, size, attribs);
@@ -58,6 +59,10 @@ implementations(
         ]
     },
 
+    arcLength,
+    (rect: Rect2) =>
+        2 * (rect.size[0] * rect.size[1]),
+
     area,
     (rect: Rect2) =>
         rect.size[0] * rect.size[1],

packages/geom2/src/triangle.ts

@@ -11,6 +11,7 @@ import { perpendicularLeft2 } from "@thi.ng/vectors3/perpendicular";
 import { signedArea2 } from "@thi.ng/vectors3/signed-area";
 import { sub } from "@thi.ng/vectors3/sub";
 import {
+    arcLength,
     area,
     Attribs,
     bounds,
@@ -50,6 +51,7 @@ implementations(
             bounds,
         ],
         [Type.POLYGON2]: [
+            arcLength,
             clipConvex,
             edges,
             perimeter,