From 2a65bc90607c1b5e9b1beb460bc81a448b011427 Mon Sep 17 00:00:00 2001
From: tome9111991 <57866234+tome9111991@users.noreply.github.com>
Date: Sat, 10 Jan 2026 19:33:34 +0100
Subject: [PATCH] Fix dark color rendering in G-code preview by using additive
 specular lighting

---
 src/libvgcode/src/Shaders.hpp | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/src/libvgcode/src/Shaders.hpp b/src/libvgcode/src/Shaders.hpp
index 826f9a4805..2d9b293724 100644
--- a/src/libvgcode/src/Shaders.hpp
+++ b/src/libvgcode/src/Shaders.hpp
@@ -40,11 +40,13 @@ static const char* Segments_Vertex_Shader =
 "  float f = 1.0 / 255.0f;\n"
 "  return f * vec3(r, g, b);\n"
 "}\n"
-"float lighting(vec3 eye_position, vec3 eye_normal) {\n"
+"float get_diffuse(vec3 eye_normal) {\n"
 "  float top_diffuse = light_top_diffuse * max(dot(eye_normal, light_top_dir), 0.0);\n"
 "  float front_diffuse = light_front_diffuse * max(dot(eye_normal, light_front_dir), 0.0);\n"
-"  float top_specular = light_top_specular * pow(max(dot(-normalize(eye_position), reflect(-light_top_dir, eye_normal)), 0.0), light_top_shininess);\n"
-"  return ambient + top_diffuse + front_diffuse + top_specular + emission;\n"
+"  return ambient + top_diffuse + front_diffuse + emission;\n"
+"}\n"
+"float get_specular(vec3 eye_position, vec3 eye_normal) {\n"
+"  return light_top_specular * pow(max(dot(-normalize(eye_position), reflect(-light_top_dir, eye_normal)), 0.0), light_top_shininess);\n"
 "}\n"
 "void main() {\n"
 "  int id_a = int(texelFetch(segment_index_tex, gl_InstanceID).r);\n"
@@ -133,7 +135,7 @@ static const char* Segments_Vertex_Shader =
 "  vec3 eye_position = (view_matrix * vec4(pos, 1.0)).xyz;\n"
 "  vec3 eye_normal = (view_matrix * vec4(normalize(pos - endpoint_pos), 0.0)).xyz;\n"
 "  vec3 color_base = decode_color(texelFetch(color_tex, id).r);\n"
-"  color = color_base * lighting(eye_position, eye_normal);\n"
+"  color = color_base * get_diffuse(eye_normal) + vec3(get_specular(eye_position, eye_normal));\n"
 "  gl_Position = projection_matrix * vec4(eye_position, 1.0);\n"
 "}\n";
 
@@ -177,11 +179,13 @@ static const char* Options_Vertex_Shader =
 "  float f = 1.0 / 255.0f;\n"
 "  return f * vec3(r, g, b);\n"
 "}\n"
-"float lighting(vec3 eye_position, vec3 eye_normal) {\n"
+"float get_diffuse(vec3 eye_normal) {\n"
 "  float top_diffuse = light_top_diffuse * max(dot(eye_normal, light_top_dir), 0.0);\n"
 "  float front_diffuse = light_front_diffuse * max(dot(eye_normal, light_front_dir), 0.0);\n"
-"  float top_specular = light_top_specular * pow(max(dot(-normalize(eye_position), reflect(-light_top_dir, eye_normal)), 0.0), light_top_shininess);\n"
-"  return ambient + top_diffuse + front_diffuse + top_specular + emission;\n"
+"  return ambient + top_diffuse + front_diffuse + emission;\n"
+"}\n"
+"float get_specular(vec3 eye_position, vec3 eye_normal) {\n"
+"  return light_top_specular * pow(max(dot(-normalize(eye_position), reflect(-light_top_dir, eye_normal)), 0.0), light_top_shininess);\n"
 "}\n"
 "void main() {\n"
 "  int id = int(texelFetch(segment_index_tex, gl_InstanceID).r);\n"
@@ -195,7 +199,7 @@ static const char* Options_Vertex_Shader =
 "  vec3 eye_position = (view_matrix * vec4(scale_matrix * in_position + offset, 1.0)).xyz;\n"
 "  vec3 eye_normal = (view_matrix * vec4(in_normal, 0.0)).xyz;\n"
 "  vec3 color_base = decode_color(texelFetch(color_tex, id).r);\n"
-"  color = color_base * lighting(eye_position, eye_normal);\n"
+"  color = color_base * get_diffuse(eye_normal) + vec3(get_specular(eye_position, eye_normal));\n"
 "  gl_Position = projection_matrix * vec4(eye_position, 1.0);\n"
 "}\n";