Merge pull request #1480 from libigl/double-sided-lighting

Toggle double sided lighting

include/igl/opengl/MeshGL.cpp

@@ -220,6 +220,7 @@ R"(#version 150
   uniform float specular_exponent;
   uniform float lighting_factor;
   uniform float texture_factor;
+  uniform float double_sided;
   out vec4 outColor;
   void main()
   {
@@ -228,13 +229,13 @@ R"(#version 150
     vec3 vector_to_light_eye = light_position_eye - position_eye;
     vec3 direction_to_light_eye = normalize (vector_to_light_eye);
     float dot_prod = dot (direction_to_light_eye, normalize(normal_eye));
-    float clamped_dot_prod = max (dot_prod, 0.0);
+    float clamped_dot_prod = abs(max (dot_prod, -double_sided));
     vec3 Id = Ld * vec3(Kdi) * clamped_dot_prod;    // Diffuse intensity
 
     vec3 reflection_eye = reflect (-direction_to_light_eye, normalize(normal_eye));
     vec3 surface_to_viewer_eye = normalize (-position_eye);
     float dot_prod_specular = dot (reflection_eye, surface_to_viewer_eye);
-    dot_prod_specular = float(abs(dot_prod)==dot_prod) * max (dot_prod_specular, 0.0);
+    dot_prod_specular = float(abs(dot_prod)==dot_prod) * abs(max (dot_prod_specular, -double_sided));
     float specular_factor = pow (dot_prod_specular, specular_exponent);
     vec3 Is = Ls * vec3(Ksi) * specular_factor;    // specular intensity
     vec4 color = vec4(lighting_factor * (Is + Id) + Ia + (1.0-lighting_factor) * vec3(Kdi),(Kai.a+Ksi.a+Kdi.a)/3);

include/igl/opengl/ViewerCore.cpp

@@ -172,6 +172,7 @@ IGL_INLINE void igl::opengl::ViewerCore::draw(
   GLint lighting_factori      = glGetUniformLocation(data.meshgl.shader_mesh,"lighting_factor");
   GLint fixed_colori          = glGetUniformLocation(data.meshgl.shader_mesh,"fixed_color");
   GLint texture_factori       = glGetUniformLocation(data.meshgl.shader_mesh,"texture_factor");
+  GLint double_sidedi         = glGetUniformLocation(data.meshgl.shader_mesh,"double_sided");
 
   glUniform1f(specular_exponenti, data.shininess);
   glUniform3fv(light_position_eyei, 1, light_position.data());
@@ -185,6 +186,7 @@ IGL_INLINE void igl::opengl::ViewerCore::draw(
     {
       // Texture
       glUniform1f(texture_factori, is_set(data.show_texture) ? 1.0f : 0.0f);
+      glUniform1f(double_sidedi, data.double_sided ? 1.0f : 0.0f);
       data.meshgl.draw_mesh(true);
       glUniform1f(texture_factori, 0.0f);
     }

include/igl/opengl/ViewerData.cpp

@@ -23,6 +23,8 @@ IGL_INLINE igl::opengl::ViewerData::ViewerData()
 : dirty(MeshGL::DIRTY_ALL),
   show_faces        (~unsigned(0)),
   show_lines        (~unsigned(0)),
+  face_based        (false),
+  double_sided      (false),
   invert_normals    (false),
   show_overlay      (~unsigned(0)),
   show_overlay_depth(~unsigned(0)),
@@ -449,6 +451,8 @@ IGL_INLINE void igl::opengl::ViewerData::clear()
   labels_strings.clear();
 
   face_based = false;
+  double_sided = false;
+  invert_normals = false;
   show_texture = false;
 }
 

include/igl/opengl/ViewerData.h

@@ -240,6 +240,9 @@ public:
   // Enable per-face or per-vertex properties
   bool face_based;
 
+  // Enable double-sided lighting on faces
+  bool double_sided;
+
   // Invert mesh normals
   bool invert_normals;
 
@@ -321,6 +324,7 @@ namespace igl
       SERIALIZE_MEMBER(show_faceid);
       SERIALIZE_MEMBER(show_labels);
       SERIALIZE_MEMBER(show_texture);
+      SERIALIZE_MEMBER(double_sided);
       SERIALIZE_MEMBER(point_size);
       SERIALIZE_MEMBER(line_width);
       SERIALIZE_MEMBER(line_color);

include/igl/opengl/glfw/Viewer.cpp

@@ -1,4 +1,4 @@
-// This file is part of libigl, a simple c++ geometry processing library. 
+// This file is part of libigl, a simple c++ geometry processing library.
 //
 // Copyright (C) 2014 Daniele Panozzo <[email protected]>
 //
@@ -354,6 +354,7 @@ namespace glfw
     const std::string usage(R"(igl::opengl::glfw::Viewer usage:
   [drag]  Rotate scene
   A,a     Toggle animation (tight draw loop)
+  D,d     Toggle double sided lighting
   F,f     Toggle face based
   I,i     Toggle invert normals
   L,l     Toggle wireframe
@@ -527,6 +528,12 @@ namespace glfw
         core().is_animating = !core().is_animating;
         return true;
       }
+      case 'D':
+      case 'd':
+      {
+        data().double_sided = !data().double_sided;
+        return true;
+      }
       case 'F':
       case 'f':
       {