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/controller/gamecontext.ts | 49 +++++++++++++++++++++++++++----------------
 src/math/line.ts              | 45 ++++++++++++++++++++-------------------
 2 files changed, 55 insertions(+), 39 deletions(-)

(limited to 'src')

diff --git a/src/controller/gamecontext.ts b/src/controller/gamecontext.ts
index cda47a5..295872d 100644
--- a/src/controller/gamecontext.ts
+++ b/src/controller/gamecontext.ts
@@ -6,7 +6,7 @@ import { loadMap } from '../view/map';
 import { Renderer } from '../view/renderer/renderer';
 import { SpriteView } from '../view/sprite';
 
-import { LineSegment } from '../math/line';
+import { LineSegment, Movement } from '../math/line';
 import { getJSON } from '../util';
 
 import { vec2 } from 'gl-matrix';
@@ -40,10 +40,25 @@ export class GameContext {
 	private readonly entityMovement: vec2 = vec2.create();
 
 	private readonly walls: LineSegment[] = [
-		new LineSegment(vec2.fromValues(1, 1), vec2.fromValues(1, 0), 10),
-		new LineSegment(vec2.fromValues(11, 1), vec2.fromValues(0, 1), 10),
-		new LineSegment(vec2.fromValues(11, 11), vec2.fromValues(-1, 0), 10),
-		new LineSegment(vec2.fromValues(1, 11), vec2.fromValues(0, -1), 10),
+		LineSegment.fromPoints(vec2.fromValues(1, 1), vec2.fromValues(11, 1)),
+
+		LineSegment.fromPoints(vec2.fromValues(11, 1), vec2.fromValues(11, 5)),
+		LineSegment.fromPoints(vec2.fromValues(11, 5), vec2.fromValues(12, 5)),
+		LineSegment.fromPoints(vec2.fromValues(12, 5), vec2.fromValues(12, 7)),
+		LineSegment.fromPoints(vec2.fromValues(12, 7), vec2.fromValues(11, 7)),
+		LineSegment.fromPoints(vec2.fromValues(11, 7), vec2.fromValues(11, 11)),
+
+		LineSegment.fromPoints(vec2.fromValues(11, 11), vec2.fromValues(7, 11)),
+		LineSegment.fromPoints(vec2.fromValues(7, 11), vec2.fromValues(7, 12)),
+		LineSegment.fromPoints(vec2.fromValues(7, 12), vec2.fromValues(5, 12)),
+		LineSegment.fromPoints(vec2.fromValues(5, 12), vec2.fromValues(5, 11)),
+		LineSegment.fromPoints(vec2.fromValues(5, 11), vec2.fromValues(1, 11)),
+
+		LineSegment.fromPoints(vec2.fromValues(1, 11), vec2.fromValues(1, 7)),
+		LineSegment.fromPoints(vec2.fromValues(1, 7), vec2.fromValues(0, 7)),
+		LineSegment.fromPoints(vec2.fromValues(0, 7), vec2.fromValues(0, 5)),
+		LineSegment.fromPoints(vec2.fromValues(0, 5), vec2.fromValues(1, 5)),
+		LineSegment.fromPoints(vec2.fromValues(1, 5), vec2.fromValues(1, 1)),
 	];
 
 	private constructor(
@@ -70,34 +85,32 @@ export class GameContext {
 	}
 
 	private updateStep(): void {
-		let move = new LineSegment(this.entityPos, this.entityMovement, this.speed);
-		const p = vec2.create();
+		const dest = vec2.scaleAndAdd(vec2.create(), this.entityPos, this.entityMovement, this.speed);
+		const dest2 = vec2.create();
 
 		let rescan = true;
 
 		while (rescan) {
 			rescan = false;
 
-			for (const w of this.walls) {
-				if (!w.collidesMove(move))
-					continue;
+			if (vec2.equals(dest, this.entityPos))
+				return;
 
-				move.getP2(p);
-				w.projectPoint(p, p);
+			const move = new Movement(this.entityPos, dest);
 
-				const move2 = LineSegment.fromPoints(this.entityPos, p);
-				if (move2.l === 0)
-					return;
+			for (const w of this.walls) {
+				if (!w.collidesMove(dest2, move))
+					continue;
 
-				if (!move.equals(move2)) {
-					move = move2;
+				if (!vec2.exactEquals(dest, dest2)) {
+					vec2.copy(dest, dest2);
 					rescan = true;
 					break;
 				}
 			}
 		}
 
-		move.getP2(this.entityPos);
+		vec2.copy(this.entityPos, dest);
 	}
 
 	private update(time: number): void {
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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