From acb4b1c6b3e12422c94ffc31a1fb61594543e9ac Mon Sep 17 00:00:00 2001
From: Grant Sanderson <grant@3blue1brown.com>
Date: Thu, 2 Feb 2023 12:04:23 -0800
Subject: [PATCH] Finalize color at the vertex level, rather than the fragment
 level, for fill

---
 manimlib/shaders/quadratic_bezier_fill/frag.glsl | 14 ++++++--------
 manimlib/shaders/quadratic_bezier_fill/geom.glsl | 10 ++++------
 2 files changed, 10 insertions(+), 14 deletions(-)

diff --git a/manimlib/shaders/quadratic_bezier_fill/frag.glsl b/manimlib/shaders/quadratic_bezier_fill/frag.glsl
index 22d0edfb..4cfed975 100644
--- a/manimlib/shaders/quadratic_bezier_fill/frag.glsl
+++ b/manimlib/shaders/quadratic_bezier_fill/frag.glsl
@@ -6,16 +6,12 @@ in vec4 color;
 in float fill_all;
 in float orientation;
 in vec2 uv_coords;
-in vec3 point;
-in vec3 unit_normal;
 
 out vec4 frag_color;
 
-#INSERT finalize_color.glsl
-
 void main() {
     if (color.a == 0) discard;
-    frag_color = finalize_color(color, point, unit_normal);
+    frag_color = color;
     /*
     We want negatively oriented triangles to be canceled with positively
     oriented ones. The easiest way to do this is to give them negative alpha,
@@ -33,9 +29,11 @@ void main() {
     cap is to make sure the original fragment color can be recovered even after
     blending with an (alpha = 1) color.
     */
-    float a = 0.95 * frag_color.a;
-    if(winding && orientation < 0) a = -a / (1 - a);
-    frag_color.a = a;
+    if(winding){
+        float a = 0.95 * frag_color.a;
+        if(orientation < 0) a = -a / (1 - a);
+        frag_color.a = a;
+    }
 
     if (bool(fill_all)) return;
 
diff --git a/manimlib/shaders/quadratic_bezier_fill/geom.glsl b/manimlib/shaders/quadratic_bezier_fill/geom.glsl
index c9428e67..99e10049 100644
--- a/manimlib/shaders/quadratic_bezier_fill/geom.glsl
+++ b/manimlib/shaders/quadratic_bezier_fill/geom.glsl
@@ -14,8 +14,6 @@ in vec3 v_unit_normal[3];
 out vec4 color;
 out float fill_all;
 out float orientation;
-out vec3 point;
-out vec3 unit_normal;
 // uv space is where the curve coincides with y = x^2
 out vec2 uv_coords;
 
@@ -28,9 +26,12 @@ const vec2 SIMPLE_QUADRATIC[3] = vec2[3](
 
 // Analog of import for manim only
 #INSERT emit_gl_Position.glsl
+#INSERT finalize_color.glsl
 
 
 void emit_triangle(vec3 points[3], vec4 v_color[3]){
+    vec3 unit_normal = v_unit_normal[1];
+
     orientation = sign(determinant(mat3(
         unit_normal,
         points[1] - points[0],
@@ -39,8 +40,7 @@ void emit_triangle(vec3 points[3], vec4 v_color[3]){
 
     for(int i = 0; i < 3; i++){
         uv_coords = SIMPLE_QUADRATIC[i];
-        color = v_color[i];
-        point = points[i];
+        color = finalize_color(v_color[i], points[i], unit_normal);
         emit_gl_Position(points[i]);
         EmitVertex();
     }
@@ -61,8 +61,6 @@ void main(){
     // the first anchor is set equal to that anchor
     if (verts[0] == verts[1]) return;
 
-    unit_normal = v_unit_normal[1];
-
     if(winding){
         // Emit main triangle
         fill_all = 1.0;