From d39fea0d4dffd793ce48cc79fd77206f361fd0fb Mon Sep 17 00:00:00 2001
From: Grant Sanderson <grant@3blue1brown.com>
Date: Wed, 18 Jan 2023 12:52:05 -0800
Subject: [PATCH] A few small fixes

---
 manimlib/shaders/quadratic_bezier_stroke/geom.glsl | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/manimlib/shaders/quadratic_bezier_stroke/geom.glsl b/manimlib/shaders/quadratic_bezier_stroke/geom.glsl
index 4fa7c8d1..9e2f5461 100644
--- a/manimlib/shaders/quadratic_bezier_stroke/geom.glsl
+++ b/manimlib/shaders/quadratic_bezier_stroke/geom.glsl
@@ -63,7 +63,7 @@ void create_joint(
     out vec3 changing_c1
 ){
     float cos_angle = joint_product.w;
-    if(cos_angle > COS_THRESHOLD || int(joint_type) == NO_JOINT){
+    if(abs(cos_angle) > COS_THRESHOLD || int(joint_type) == NO_JOINT){
         // No joint
         changing_c0 = static_c0;
         changing_c1 = static_c1;
@@ -105,7 +105,7 @@ void get_corners(
 
     // Add correction for sharp angles to prevent weird bevel effects
     if(v_joint_product[0].w < -0.5) buff0 *= 2 * (v_joint_product[0].w + 1.0);
-    if(v_joint_product[2].w < -0.5) buff2 *= 2 * (v_joint_product[0].w + 1.0);
+    if(v_joint_product[2].w < -0.5) buff2 *= 2 * (v_joint_product[2].w + 1.0);
 
     // Unit normal and joint angles
     vec3 normal0 = get_joint_unit_normal(v_joint_product[0]);
@@ -113,8 +113,9 @@ void get_corners(
     // Set global unit normal
     unit_normal = normal0;
 
-    // Make sure normals point in the same direction
-    if(dot(normal0, normal2) < 0) buff2 *= -1;
+    // Choose the "outward" normal direction
+    normal0 *= sign(normal0.z);
+    normal2 *= sign(normal2.z);
 
     vec3 p0_perp;
     vec3 p2_perp;