From ff090c016f320bafba498bff996bdd980057e980 Mon Sep 17 00:00:00 2001
From: Grant Sanderson <grant@3blue1brown.com>
Date: Thu, 22 Dec 2022 11:46:51 -0700
Subject: [PATCH] Use only anchors to compute area vector

---
 manimlib/mobject/types/vectorized_mobject.py | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/manimlib/mobject/types/vectorized_mobject.py b/manimlib/mobject/types/vectorized_mobject.py
index 3221beaf..c3ea4709 100644
--- a/manimlib/mobject/types/vectorized_mobject.py
+++ b/manimlib/mobject/types/vectorized_mobject.py
@@ -758,9 +758,10 @@ class VMobject(Mobject):
         if not self.has_points():
             return np.zeros(3)
 
+        nppc = self.n_points_per_curve
         points = self.get_points()
-        p0 = points[:-1]
-        p1 = points[1:]
+        p0 = points[0::nppc]
+        p1 = points[nppc - 1::nppc]
 
         # Each term goes through all edges [(x1, y1, z1), (x2, y2, z2)]
         return 0.5 * np.array([
@@ -1023,10 +1024,9 @@ class VMobject(Mobject):
         super().set_points(points)
         return self
 
+    @triggers_refreshed_triangulation
     def append_points(self, points: Vect3Array):
         super().append_points(points)
-        self.refresh_unit_normal()
-        self.refresh_triangulation()
         return self
 
     @triggers_refreshed_triangulation