From 6a02ea105a4e15e9f36a5b2d7d0a26169164fb1d Mon Sep 17 00:00:00 2001
From: Matthias Schiffer <mschiffer@universe-factory.net>
Date: Sun, 4 Nov 2018 22:02:19 +0100
Subject: Fix rounding issues in collision handling

---
 src/math/line.ts | 45 ++++++++++++++++++++++++---------------------
 1 file changed, 24 insertions(+), 21 deletions(-)

(limited to 'src/math/line.ts')

diff --git a/src/math/line.ts b/src/math/line.ts
index 98e126b..902c9b6 100644
--- a/src/math/line.ts
+++ b/src/math/line.ts
@@ -37,9 +37,23 @@ export class Line {
 		const d2 = d / crossz(this.v, l2.v);
 		return vec2.scaleAndAdd(out, l2.p, l2.v, d2);
 	}
+}
+
+export class Movement {
+	public readonly v: vec2;
 
-	public equals(l2: Line): boolean {
-		return vec2.equals(this.p, l2.p) && vec2.equals(this.v, l2.v);
+	constructor(
+		public readonly p1: vec2,
+		public readonly p2: vec2,
+	) {
+		this.v = vec2.sub(vec2.create(), p2, p1);
+	}
+
+	public intersectLine(out: vec2, l: Line): vec2 {
+		const vp = vec2.sub(vec2.create(), l.p, this.p1);
+		const d = crossz(vp, this.v);
+		const d2 = d / crossz(this.v, l.v);
+		return vec2.scaleAndAdd(out, l.p, l.v, d2);
 	}
 }
 
@@ -69,30 +83,19 @@ export class LineSegment extends Line {
 		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))
+	public collidesMove(out: vec2, move: Movement): boolean {
+		if (this.distancePoint(move.p1) < 0)
 			return false;
 
-		return true;
-	}
+		if (this.distancePoint(move.p2) >= 0)
+			return false;
 
-	public collidesMove(move: LineSegment): boolean {
-		if (!this.collidesLineSegment(move))
+		const x = move.intersectLine(vec2.create(), this);
+		if (!this.collidesPoint(x))
 			return false;
 
-		const p2 = move.getP2(vec2.create());
-		return this.distancePoint(p2) < 0;
-	}
+		this.projectPoint(out, move.p2);
 
-	public equals(l2: LineSegment): boolean {
-		return super.equals(l2) && this.l === l2.l;
+		return true;
 	}
 }
-- 
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