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-rw-r--r--src/math/line.ts98
1 files changed, 98 insertions, 0 deletions
diff --git a/src/math/line.ts b/src/math/line.ts
new file mode 100644
index 0000000..98e126b
--- /dev/null
+++ b/src/math/line.ts
@@ -0,0 +1,98 @@
+import { mat2, vec2 } from 'gl-matrix';
+
+const rot90 = mat2.fromRotation(mat2.create(), Math.PI / 2);
+
+export function normal(out: vec2, a: vec2): vec2 {
+ return vec2.transformMat2(out, a, rot90);
+}
+
+export function crossz(a: vec2, b: vec2): number {
+ return a[0] * b[1] - a[1] * b[0];
+}
+
+export class Line {
+ constructor(
+ public readonly p: vec2,
+ public readonly v: vec2,
+ ) {}
+
+ public projectPointDistance(p2: vec2): number {
+ const v2 = vec2.sub(vec2.create(), p2, this.p);
+ return vec2.dot(this.v, v2);
+ }
+
+ public projectPoint(out: vec2, p2: vec2): vec2 {
+ const d = this.projectPointDistance(p2);
+ return vec2.scaleAndAdd(out, this.p, this.v, d);
+ }
+
+ public distancePoint(p2: vec2): number {
+ const v2 = vec2.sub(vec2.create(), p2, this.p);
+ return crossz(this.v, v2);
+ }
+
+ public intersectLine(out: vec2, l2: Line): vec2 {
+ const vp = vec2.sub(vec2.create(), l2.p, this.p);
+ const d = crossz(vp, this.v);
+ const d2 = d / crossz(this.v, l2.v);
+ return vec2.scaleAndAdd(out, l2.p, l2.v, d2);
+ }
+
+ public equals(l2: Line): boolean {
+ return vec2.equals(this.p, l2.p) && vec2.equals(this.v, l2.v);
+ }
+}
+
+export class LineSegment extends Line {
+ public static fromPoints(p1: vec2, p2: vec2): LineSegment {
+ const d = vec2.dist(p1, p2);
+ const v = vec2.sub(vec2.create(), p2, p1);
+ vec2.scale(v, v, 1 / d);
+
+ return new LineSegment(p1, v, d);
+ }
+
+ constructor(
+ p: vec2,
+ v: vec2,
+ public readonly l: number,
+ ) {
+ super(p, v);
+ }
+
+ public getP2(out: vec2): vec2 {
+ return vec2.scaleAndAdd(out, this.p, this.v, this.l);
+ }
+
+ public collidesPoint(p2: vec2): boolean {
+ const d = this.projectPointDistance(p2);
+ return (d >= 0 && d <= this.l);
+ }
+
+ public collidesLine(l2: Line): boolean {
+ const x = this.intersectLine(vec2.create(), l2);
+ return this.collidesPoint(x);
+ }
+
+ public collidesLineSegment(l2: LineSegment): boolean {
+ const x = this.intersectLine(vec2.create(), l2);
+ if (!this.collidesPoint(x))
+ return false;
+ if (!l2.collidesPoint(x))
+ return false;
+
+ return true;
+ }
+
+ public collidesMove(move: LineSegment): boolean {
+ if (!this.collidesLineSegment(move))
+ return false;
+
+ const p2 = move.getP2(vec2.create());
+ return this.distancePoint(p2) < 0;
+ }
+
+ public equals(l2: LineSegment): boolean {
+ return super.equals(l2) && this.l === l2.l;
+ }
+}