From a54f7f087a222b9f684df232b1aee661c7b9da9c Mon Sep 17 00:00:00 2001
From: Erik Onarheim <erik.onarheim@gmail.com>
Date: Fri, 17 May 2024 21:20:22 -0500
Subject: [PATCH] perf: Polygon check winding on negative scale

---
 src/engine/Collision/Colliders/PolygonCollider.ts | 6 ++++--
 src/engine/Math/affine-matrix.ts                  | 4 ++++
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/src/engine/Collision/Colliders/PolygonCollider.ts b/src/engine/Collision/Colliders/PolygonCollider.ts
index 6411bdccd..0c2a6b6db 100644
--- a/src/engine/Collision/Colliders/PolygonCollider.ts
+++ b/src/engine/Collision/Colliders/PolygonCollider.ts
@@ -372,9 +372,11 @@ export class PolygonCollider extends Collider {
     for (let i = 0; i < len; i++) {
       this._transformedPoints[i] = this._globalMatrix.multiply(points[i].clone());
     }
-    // TODO possible optimization here only check if the transform has a potentially problematic value?
     // it is possible for the transform to change the winding, scale (-1, 1) for example
-    this._checkAndUpdateWinding(this._transformedPoints);
+    const scale = this._globalMatrix.getScale();
+    if (scale.x < 0 || scale.y < 0) {
+      this._checkAndUpdateWinding(this._transformedPoints);
+    }
   }
 
   /**
diff --git a/src/engine/Math/affine-matrix.ts b/src/engine/Math/affine-matrix.ts
index dfda55551..e89159f46 100644
--- a/src/engine/Math/affine-matrix.ts
+++ b/src/engine/Math/affine-matrix.ts
@@ -151,6 +151,8 @@ export class AffineMatrix {
 
     this._scale[0] = x;
     this._scale[1] = y;
+    this._scaleSignX = sign(x);
+    this._scaleSignY = sign(y);
     return this;
   }
 
@@ -406,6 +408,8 @@ export class AffineMatrix {
   public clone(dest?: AffineMatrix): AffineMatrix {
     const mat = dest || new AffineMatrix();
     mat.data.set(this.data);
+    mat._scaleSignX = this._scaleSignX;
+    mat._scaleSignY = this._scaleSignY;
     return mat;
   }