From ebeb9148297b08554d0a2ba98460f17c02efc24f Mon Sep 17 00:00:00 2001
From: Mexicoco <146551569+Mexicoco@users.noreply.github.com>
Date: Wed, 17 Dec 2025 23:57:03 +0800
Subject: [PATCH] fix: correct 2D cross product formula in MathUtils
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The cross product formula was incorrect:
- Before: p1x * p2x - p1y * p2y (wrong)
- After: p1x * p2y - p1y * p2x (correct)

The 2D cross product (perp dot product) should compute:
A × B = Ax * By - Ay * Bx

This returns the z-component of the 3D cross product when
treating 2D vectors as 3D vectors with z=0.

Also fixed the example comment to show correct result.
---
 src/utils/MathUtils.ts | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/utils/MathUtils.ts b/src/utils/MathUtils.ts
index 0c775e5..fc8a8d4 100644
--- a/src/utils/MathUtils.ts
+++ b/src/utils/MathUtils.ts
@@ -56,7 +56,7 @@ export const lerp = mix;
  * @param p2y 第二个向量的y分量
  * @returns 叉积结果 (标量)
  * @example
- * cross(1, 0, 0, 1) // 返回 0
+ * cross(1, 0, 0, 1) // 返回 1
  */
 export function cross(
   p1x: number,
@@ -68,7 +68,7 @@ export function cross(
     if (!isNumber(p1x) || !isNumber(p1y) || !isNumber(p2x) || !isNumber(p2y)) {
       throw new Error("Invalid parameters for cross function");
     }
-    return p1x * p2x - p1y * p2y;
+    return p1x * p2y - p1y * p2x;
   } catch (error) {
     console.error("Error in cross function:", error);
     return 0;