mouse-pickeroni.cpp

// for the current mouse position on the screen, where does that correspond to in the world?
glm::vec2 Game::world_position_for_mouse(glm::vec2 const & position,
                                          glm::mat4 const & projection_matrix,
                                          glm::mat4 const & view_matrix) const
{
   auto window_dimensions = impl->main_window->get_dimensions();


   //   std::cout << fmt::format("computing world position for mouse from {} {}", mouse_x, mouse_y) << std::endl;

   float normalized_mouse_x =  (2.0f * position.x) / window_dimensions.width - 1.0f;
   float normalized_mouse_y = 1.0f - (2.0f * position.y) / window_dimensions.height;


   glm::vec3 normalized_mouse_vector = glm::vec3(normalized_mouse_x, normalized_mouse_y, 1.0f);

   glm::vec4 ray_clip = glm::vec4(normalized_mouse_vector.xy(), -1.0, 1.0);

   glm::vec4 ray_eye = glm::inverse(projection_matrix) * ray_clip;
   ray_eye = glm::vec4(ray_eye.xy(), -1.0, 0.0);

   glm::vec3 ray_world = (glm::inverse(view_matrix) * ray_eye).xyz();

   ray_world = glm::normalize(ray_world);

   float l = -(impl->camera.z / ray_world.z);


   return {impl->camera.x + l * ray_world.x, impl->camera.y + l * ray_world.y};
}