feat(geom): add splitNearPoint() for line & polyline, update Sampler

packages/geom3/src/internal/sampler.ts

@@ -128,6 +128,10 @@ export class Sampler {
         return [head, tail];
     }
 
+    splitNear(p: ReadonlyVec) {
+        return this.splitAt(this.closestT(p));
+    }
+
     indexAt(t: number) {
         const pts = this.points;
         const n = pts.length - 1;

packages/geom3/src/ops/split-near.ts

@@ -1,14 +1,37 @@
 import { defmulti } from "@thi.ng/defmulti";
+import { clamp01 } from "@thi.ng/math";
 import { ReadonlyVec } from "@thi.ng/vectors3";
 import {
     Cubic,
     IShape,
+    Line,
+    Polyline,
     Quadratic,
     Type
 } from "../api";
+import { closestCoeff } from "../internal/closest-point";
+import { copyPoints } from "../internal/copy-points";
 import { dispatch } from "../internal/dispatch";
-import { splitCubicNear, splitQuadraticNear } from "../internal/split";
+import { Sampler } from "../internal/sampler";
+import { splitCubicNear, splitLine, splitQuadraticNear } from "../internal/split";
 
+/**
+ * Similar to `splitAt`, but instead of taking a normalized parametric
+ * split position, splits the given curve at the closest point to `p`.
+ * Returns tuple of split shapes of same type as `shape`.
+ *
+ * Implemented for:
+ *
+ * - Cubic
+ * - Line
+ * - Polyline
+ * - Quadratic
+ *
+ * @see splitAt
+ *
+ * @param shape
+ * @param p
+ */
 export const splitNearPoint = defmulti<IShape, ReadonlyVec, IShape[]>(dispatch);
 
 splitNearPoint.addAll({
@@ -18,6 +41,19 @@ splitNearPoint.addAll({
             splitCubicNear(p, points[0], points[1], points[2], points[3])
                 .map((pts) => new Cubic(pts, { ...attribs })),
 
+    [Type.LINE]:
+        ($: Line, p) => {
+            const t = closestCoeff(p, $.points[0], $.points[1]) || 0;
+            return splitLine($.points[0], $.points[1], clamp01(t))
+                .map((pts) => new Line(pts, { ...$.attribs }));
+        },
+
+    [Type.POLYLINE]:
+        ($: Polyline, p) =>
+            new Sampler($.points)
+                .splitNear(p)
+                .map((pts) => new Polyline(copyPoints(pts), { ...$.attribs })),
+
     [Type.QUADRATIC]:
         ({ points, attribs }: Quadratic, p) =>
             splitQuadraticNear(p, points[0], points[1], points[2])