From bb27a78449216c92738c31b1fbf465e786f95aae Mon Sep 17 00:00:00 2001
From: Wallbreaker5th <3277946283@qq.com>
Date: Sat, 5 Jun 2021 17:33:54 +0800
Subject: [PATCH 1/2] fix: checking whether normal is facing the camera.

---
 manimlib/shaders/inserts/finalize_color.glsl | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/manimlib/shaders/inserts/finalize_color.glsl b/manimlib/shaders/inserts/finalize_color.glsl
index 0664deb0..f9d37cf3 100644
--- a/manimlib/shaders/inserts/finalize_color.glsl
+++ b/manimlib/shaders/inserts/finalize_color.glsl
@@ -17,16 +17,17 @@ vec4 add_light(vec4 color,
                float shadow){
     if(gloss == 0.0 && shadow == 0.0) return color;
 
-    // TODO, do we actually want this?  It effectively treats surfaces as two-sided
-    if(unit_normal.z < 0){
-            unit_normal *= -1;
-    }
-
     // TODO, read this in as a uniform?
     float camera_distance = 6;  
     // Assume everything has already been rotated such that camera is in the z-direction
     vec3 to_camera = vec3(0, 0, camera_distance) - point;
     vec3 to_light = light_coords - point;
+
+    // TODO, do we actually want this?  It effectively treats surfaces as two-sided
+    if(dot(to_camera,unit_normal) < 0){
+            unit_normal *= -1;
+    }
+
     vec3 light_reflection = -to_light + 2 * unit_normal * dot(to_light, unit_normal);
     float dot_prod = dot(normalize(light_reflection), normalize(to_camera));
     float shine = gloss * exp(-3 * pow(1 - dot_prod, 2));

From 442e7fc14daa3f3ddba467bfe606cf0754411c6d Mon Sep 17 00:00:00 2001
From: Wallbreaker5th <3277946283@qq.com>
Date: Sat, 5 Jun 2021 17:43:32 +0800
Subject: [PATCH 2/2] Use focal_distance as camera_distance in shaders.

---
 manimlib/shaders/inserts/finalize_color.glsl | 3 +--
 manimlib/shaders/surface/frag.glsl           | 1 +
 manimlib/shaders/textured_surface/frag.glsl  | 1 +
 manimlib/shaders/true_dot/frag.glsl          | 1 +
 4 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/manimlib/shaders/inserts/finalize_color.glsl b/manimlib/shaders/inserts/finalize_color.glsl
index f9d37cf3..e7b64eee 100644
--- a/manimlib/shaders/inserts/finalize_color.glsl
+++ b/manimlib/shaders/inserts/finalize_color.glsl
@@ -17,8 +17,7 @@ vec4 add_light(vec4 color,
                float shadow){
     if(gloss == 0.0 && shadow == 0.0) return color;
 
-    // TODO, read this in as a uniform?
-    float camera_distance = 6;  
+    float camera_distance = focal_distance;
     // Assume everything has already been rotated such that camera is in the z-direction
     vec3 to_camera = vec3(0, 0, camera_distance) - point;
     vec3 to_light = light_coords - point;
diff --git a/manimlib/shaders/surface/frag.glsl b/manimlib/shaders/surface/frag.glsl
index db905275..707621a1 100644
--- a/manimlib/shaders/surface/frag.glsl
+++ b/manimlib/shaders/surface/frag.glsl
@@ -3,6 +3,7 @@
 uniform vec3 light_source_position;
 uniform float gloss;
 uniform float shadow;
+uniform float focal_distance;
 
 in vec3 xyz_coords;
 in vec3 v_normal;
diff --git a/manimlib/shaders/textured_surface/frag.glsl b/manimlib/shaders/textured_surface/frag.glsl
index ab45dad6..616b06e2 100644
--- a/manimlib/shaders/textured_surface/frag.glsl
+++ b/manimlib/shaders/textured_surface/frag.glsl
@@ -6,6 +6,7 @@ uniform float num_textures;
 uniform vec3 light_source_position;
 uniform float gloss;
 uniform float shadow;
+uniform float focal_distance;
 
 in vec3 xyz_coords;
 in vec3 v_normal;
diff --git a/manimlib/shaders/true_dot/frag.glsl b/manimlib/shaders/true_dot/frag.glsl
index a8965359..0be9a2ab 100644
--- a/manimlib/shaders/true_dot/frag.glsl
+++ b/manimlib/shaders/true_dot/frag.glsl
@@ -4,6 +4,7 @@ uniform vec3 light_source_position;
 uniform float gloss;
 uniform float shadow;
 uniform float anti_alias_width;
+uniform float focal_distance;
 
 in vec4 color;
 in float radius;