Rename add_light -> finalize_color and leave room for other color manipulations

manimlib/shaders/inserts/add_light.glsl

@@ -30,4 +30,14 @@ vec4 add_light(vec4 color,
             darkening * mix(color.rgb, vec3(1.0), shine),
             color.a
     );
+}
+
+vec4 finalize_color(vec4 color,
+                    vec3 point,
+                    vec3 unit_normal,
+                    vec3 light_coords,
+                    float gloss,
+                    float shadow){
+    // Put insertion here instead
+    return add_light(color, point, unit_normal, light_coords, gloss, shadow);
 }

manimlib/shaders/inserts/finalize_color.glsl

@@ -0,0 +1,42 @@
+///// INSERT COLOR_MAP FUNCTION HERE /////
+
+vec4 add_light(vec4 color,
+               vec3 point,
+               vec3 unit_normal,
+               vec3 light_coords,
+               float gloss,
+               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;
+    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));
+    float dp2 = dot(normalize(to_light), unit_normal);
+    float darkening = mix(1, max(dp2, 0), shadow);
+    return vec4(
+            darkening * mix(color.rgb, vec3(1.0), shine),
+            color.a
+    );
+}
+
+vec4 finalize_color(vec4 color,
+                    vec3 point,
+                    vec3 unit_normal,
+                    vec3 light_coords,
+                    float gloss,
+                    float shadow){
+    ///// INSERT COLOR FUNCTION HERE /////
+    // The line above may be replaced by arbitrary code snippets, as per
+    // the method Mobject.set_color_by_code
+    return add_light(color, point, unit_normal, light_coords, gloss, shadow);
+}

manimlib/shaders/quadratic_bezier_fill/geom.glsl

@@ -9,7 +9,7 @@ uniform float anti_alias_width;
 uniform vec2 frame_shape;
 uniform float focal_distance;
 uniform float is_fixed_in_frame;
-// Needed for add_light
+// Needed for finalize_color
 uniform vec3 light_source_position;
 uniform float gloss;
 uniform float shadow;
@@ -35,11 +35,11 @@ out float bezier_degree;
 #INSERT quadratic_bezier_geometry_functions.glsl
 #INSERT get_gl_Position.glsl
 #INSERT get_unit_normal.glsl
-#INSERT add_light.glsl
+#INSERT finalize_color.glsl
 
 
 void emit_vertex_wrapper(vec3 point, int index){
-    color = add_light(
+    color = finalize_color(
         v_color[index],
         point,
         v_global_unit_normal[index],

manimlib/shaders/quadratic_bezier_stroke/geom.glsl

@@ -52,7 +52,7 @@ const float PI = 3.141592653;
 #INSERT quadratic_bezier_geometry_functions.glsl
 #INSERT get_gl_Position.glsl
 #INSERT get_unit_normal.glsl
-#INSERT add_light.glsl
+#INSERT finalize_color.glsl
 
 
 void flatten_points(in vec3[3] points, out vec2[3] flat_points){
@@ -254,7 +254,7 @@ void main() {
         // Apply some lighting to the color before sending out.
         // vec3 xyz_coords = vec3(corners[i], controls[index_map[i]].z);
         vec3 xyz_coords = vec3(corners[i], controls[index_map[i]].z);
-        color = add_light(
+        color = finalize_color(
             v_color[index_map[i]],
             xyz_coords,
             v_global_unit_normal[index_map[i]],

manimlib/shaders/surface/frag.glsl

@@ -10,10 +10,10 @@ in vec4 v_color;
 
 out vec4 frag_color;
 
-#INSERT add_light.glsl
+#INSERT finalize_color.glsl
 
 void main() {
-    frag_color = add_light(
+    frag_color = finalize_color(
         v_color,
         xyz_coords,
         normalize(v_normal),

manimlib/shaders/textured_surface/frag.glsl

@@ -14,7 +14,7 @@ in float v_opacity;
 
 out vec4 frag_color;
 
-#INSERT add_light.glsl
+#INSERT finalize_color.glsl
 
 const float dark_shift = 0.2;
 
@@ -30,7 +30,7 @@ void main() {
         color = mix(dark_color, color, alpha);
     }
 
-    frag_color = add_light(
+    frag_color = finalize_color(
         color,
         xyz_coords,
         normalize(v_normal),

manimlib/shaders/true_dot/frag.glsl

@@ -12,7 +12,7 @@ in vec2 point;
 
 out vec4 frag_color;
 
-#INSERT add_light.glsl
+#INSERT finalize_color.glsl
 
 void main() {
     vec2 diff = point - center;
@@ -22,7 +22,7 @@ void main() {
         discard;
     }
     vec3 normal = vec3(diff / radius, sqrt(1 - (dist * dist) / (radius * radius)));
-    frag_color = add_light(
+    frag_color = finalize_color(
         color,
         vec3(point.xy, 0.0),
         normal,