Fix light to consider object transformation

data/shaders/vertex.glsl

@@ -6,9 +6,11 @@ varying vec2 f_tex_coord;
 varying float light_weight;
 
 uniform mat4 mvp;
+uniform mat3 local_modelview;
 
 void main(void) {
   gl_Position = mvp * position;
   f_tex_coord = tex_coord;
-  light_weight = max(dot(normal, vec3(0.0, 0.0, 1.0)), 0.0);
+  vec3 transformed_normal = local_modelview * normal;
+  light_weight = max(dot(transformed_normal, vec3(0.0, 0.0, 1.0)), 0.0);
 }

src/gl.hpp

@@ -5,5 +5,6 @@
 #include <GL/glfw.h>
 
 extern GLuint mvp_uniform;
+extern GLuint local_modelview_uniform;
 
 #endif // _GL_HPP_

src/main.cpp

@@ -18,6 +18,8 @@ static GLFWCALL void on_key(int key, int action);
 static EM_BOOL on_em_mousemove(int event_type, const EmscriptenMouseEvent *mouse_event, void *user_data);
 
 GLuint mvp_uniform;
+GLuint local_modelview_uniform;
+
 static GLuint texture_uniform;
 
 static bool keys[GLFW_KEY_LAST];
@@ -58,6 +60,7 @@ int main()
   program.use();
 
   mvp_uniform = program.get_uniform_location("mvp");
+  local_modelview_uniform = program.get_uniform_location("local_modelview");
 
   texture_uniform = program.get_uniform_location("texture");
   glUniform1i(texture_uniform, 0);
@@ -73,7 +76,7 @@ int main()
   teapot1 = new Object(*teapot);
   teapot1->position.x = -2.0;
   teapot1->position.z = 1.0;
-  teapot1->rotation.z = 45;
+  teapot1->angles.z = 45;
 
   bunny1 = new Object(*bunny);
   bunny1->position.x = 2.0;
@@ -133,21 +136,21 @@ void iterate()
     pos_y -= 0.1 * sin(glm::radians(delta_z));
   }
 
-  suzanne1->rotation.y = glfwGetTime() * 360 / 4;
-  teapot1->rotation.x = glfwGetTime() * 360 / 6;
-  bunny1->rotation.z = glfwGetTime() * 360 / 2;
+  suzanne1->angles.y = glfwGetTime() * 360 / 4;
+  teapot1->angles.x = glfwGetTime() * 360 / 6;
+  bunny1->angles.z = glfwGetTime() * 360 / 2;
 
   glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
 
-  glm::mat4 model = glm::translate(glm::mat4(1.0f), glm::vec3(-pos_x, -pos_y, -2.0f));
+  const glm::mat4 model = glm::translate(glm::mat4(1.0f), glm::vec3(-pos_x, -pos_y, -2.0f));
 
-  glm::mat4 view = glm::mat4(1.0f)
+  const glm::mat4 view = glm::mat4(1.0f)
     * glm::rotate(glm::mat4(1.0f), glm::radians(delta_x - 90), glm::vec3(1.0f, 0.0f, 0.0f))
     * glm::rotate(glm::mat4(1.0f), glm::radians(delta_z), glm::vec3(0.0f, 0.0f, 1.0f));
 
-  glm::mat4 projection = glm::perspective(45.0f, (float)640 / (float)480, 0.1f, 10.0f);
+  const glm::mat4 projection = glm::perspective(45.0f, (float)640 / (float)480, 0.1f, 10.0f);
 
-  glm::mat4 mvp = projection * view * model;
+  const glm::mat4 mvp = projection * view * model;
 
   suzanne1->draw(mvp);
   teapot1->draw(mvp);

src/object.cpp

@@ -5,12 +5,18 @@
 
 void Object::draw(const glm::mat4 &mvp) const
 {
-  const glm::mat4 transform = glm::translate(mvp, position)
-    * glm::rotate(glm::mat4(1.0f), glm::radians(rotation.x), glm::vec3(1.0f, 0.0f, 0.0f))
-    * glm::rotate(glm::mat4(1.0f), glm::radians(rotation.y), glm::vec3(0.0f, 1.0f, 0.0f))
-    * glm::rotate(glm::mat4(1.0f), glm::radians(rotation.z), glm::vec3(0.0f, 0.0f, 1.0f));
+  const glm::mat4 translation = glm::translate(glm::mat4(1.0f), position);
 
+  const glm::mat4 rotation =
+    glm::rotate(glm::mat4(1.0f), glm::radians(angles.z), glm::vec3(0.0f, 0.0f, 1.0f))
+    * glm::rotate(glm::mat4(1.0f), glm::radians(angles.y), glm::vec3(0.0f, 1.0f, 0.0f))
+    * glm::rotate(glm::mat4(1.0f), glm::radians(angles.x), glm::vec3(1.0f, 0.0f, 0.0f));
+
+  const glm::mat4 transform = mvp * translation * rotation;
   glUniformMatrix4fv(mvp_uniform, 1, GL_FALSE, glm::value_ptr(transform));
 
+  const glm::mat3 local_modelview = glm::transpose(glm::inverse(glm::mat3(translation * rotation)));
+  glUniformMatrix3fv(local_modelview_uniform, 1, GL_FALSE, glm::value_ptr(local_modelview));
+
   _model.draw();
 }

src/object.hpp

@@ -12,7 +12,7 @@ public:
   void draw(const glm::mat4 &mvp) const;
 
   glm::vec3 position;
-  glm::vec3 rotation;
+  glm::vec3 angles;
 
 private:
   const Model &_model;