From ba78c98a747ab0029afbbc2e9e39f636a92de068 Mon Sep 17 00:00:00 2001
From: Schluffe <schluffe@cachyos>
Date: Wed, 25 Mar 2026 21:59:04 +0100
Subject: [PATCH] Add moveAndSlide

---
 engine/system/physics.ts     | 40 +++++++++++++++++++++++++++---------
 game/entities/hero/entity.ts | 17 ++++++---------
 2 files changed, 36 insertions(+), 21 deletions(-)

diff --git a/engine/system/physics.ts b/engine/system/physics.ts
index 624378e..69edbaa 100644
--- a/engine/system/physics.ts
+++ b/engine/system/physics.ts
@@ -2,7 +2,14 @@ import type { Circle } from "#/engine/Circle.ts";
 import type { Polygon } from "#/engine/Polygon.ts";
 import { createRect, fillRect, type Rect, strokeRect } from "#/engine/Rect.ts";
 import $ from "#/engine/Scene.ts";
-import { createVector, getDistance, type Vector } from "#/engine/Vector.ts";
+import {
+	createVector,
+	getDistance,
+	getDotProduct,
+	invScale,
+	setUnitNormal,
+	type Vector,
+} from "#/engine/Vector.ts";
 import { viewport } from "#/engine/Viewport.ts";
 
 export enum Shape {
@@ -41,9 +48,6 @@ export type Collider = {
 export type Collision = {
 	cid: string;
 	normal: Vector;
-	position: Vector;
-	depth: number;
-	angle: number;
 	time: number;
 };
 
@@ -149,9 +153,15 @@ function collideWithRect(
 	other: Collider,
 ) {
 	collision.cid = cid;
-	const inflX = other.aabb.position.x - self.aabb.width;
-	const inflY = other.aabb.position.y - self.aabb.height;
-	collision.depth = getDistance(createVector(inflX, inflY), self.aabb.position);
+	const x = self.aabb.position.x - other.aabb.position.x;
+	const y = self.aabb.position.y - other.aabb.position.y;
+	if (Math.abs(x) > Math.abs(y)) {
+		collision.normal.y = 0;
+		collision.normal.x = x > 0 ? 1 : -1;
+	} else {
+		collision.normal.x = 0;
+		collision.normal.y = y > 0 ? 1 : -1;
+	}
 }
 
 function collideWithPolygon(
@@ -209,9 +219,6 @@ function createCollision(): Collision {
 	return {
 		cid: "",
 		normal: createVector(),
-		position: createVector(),
-		depth: 0,
-		angle: 0,
 		time: 0,
 	};
 }
@@ -268,3 +275,16 @@ export function moveAndCollide(
 
 	return slice;
 }
+
+export function moveAndSlide(
+	id: string,
+	velocity: Vector,
+	delta: number,
+): void {
+	const collisions = moveAndCollide(id, velocity, delta);
+	for (const collision of collisions) {
+		const dot = getDotProduct(velocity, collision.normal);
+		velocity.x -= collision.normal.x * dot;
+		velocity.y -= collision.normal.y * dot;
+	}
+}
diff --git a/game/entities/hero/entity.ts b/game/entities/hero/entity.ts
index dd402c1..d38b781 100644
--- a/game/entities/hero/entity.ts
+++ b/game/entities/hero/entity.ts
@@ -14,10 +14,12 @@ import {
 	type Collision,
 	createCollider,
 	moveAndCollide,
+	moveAndSlide,
 	Shape,
 } from "#/engine/system/physics.ts";
 import {
 	createVector,
+	getDotProduct,
 	normalize,
 	scale,
 	type Vector,
@@ -55,24 +57,17 @@ process((id, delta) => {
 	velocity.x += keyboardInput.arrowRight ? 1 : 0;
 	velocity.y -= keyboardInput.arrowUp ? 1 : 0;
 	velocity.y += keyboardInput.arrowDown ? 1 : 0;
+
 	normalize(velocity);
 	scale(velocity, speed);
+	moveAndSlide(id, velocity, delta);
 
-	let cScale = 1;
-	const collisions = moveAndCollide(id, velocity, delta);
-	for (const collision of collisions) {
-		cScale = Math.min(0, collision.time - 0.001);
-	}
-
-	position.x += velocity.x * delta * cScale;
-	position.y += velocity.y * delta * cScale;
+	position.x += velocity.x * delta;
+	position.y += velocity.y * delta;
 
 	velocity.x = 0;
 	velocity.y = 0;
 
 	fillRect(viewport.ctx, collider.aabb, "orange");
 	strokeRect(viewport.ctx, collider.aabb, "red");
-	if (collisions.some((c: Collision) => c.cid.length > 0)) {
-		fillRect(viewport.ctx, collider.aabb, "red");
-	}
 });