Add Containers scene for testing specular maps; name scenes

- Add Scene::name and show it in the scene selector (falls back to
  "Scene N" when empty; ImGui IDs keep equal names apart)
- Add a Containers scene: container2 with its specular map, arranged
  on a floor as a pyramid, a stack, loose crates and one large crate.
  Lit by 8 point and 4 spot lights, with the directional light's
  diffuse and specular turned off
- create_textured_material() takes an optional specular map, loaded
  without the checkerboard fallback like in the OBJ loader
- Add create_floor() and use it for the Backpack scene too (same
  position as before)

src/main.cpp

@@ -105,7 +105,10 @@ Rc<Scene> create_sponza_scene(const Rc<Shader>& shader);
 Rc<Scene> create_car_scene(const Rc<Shader>& shader);
 Rc<Scene> create_backpack_scene(const Rc<Shader>& shader, const Rc<Mesh>& cube_mesh);
 Rc<Scene> create_cubes_scene(const Rc<Shader>& shader, const Rc<Mesh>& cube_mesh);
-Rc<Material> create_textured_material(const Rc<Shader>& shader, const std::string& texture_path);
+Rc<Scene> create_containers_scene(const Rc<Shader>& shader, const Rc<Mesh>& cube_mesh);
+Entity create_floor(const Rc<Shader>& shader, const Rc<Mesh>& cube_mesh, float top_y);
+Rc<Material> create_textured_material(const Rc<Shader>& shader, const std::string& diffuse_path,
+                                      const std::string& specular_path = "");
 void add_random_lights(Scene& scene, int point_light_count, int spot_light_count, unsigned int seed);
 
 // Frame
@@ -210,12 +213,14 @@ std::vector<Rc<Scene>> create_scenes(const Rc<Shader>& shader, const Rc<Mesh>& c
         create_car_scene(shader),
         create_backpack_scene(shader, cube_mesh),
         create_cubes_scene(shader, cube_mesh),
+        create_containers_scene(shader, cube_mesh),
     };
 }
 
 Rc<Scene> create_sponza_scene(const Rc<Shader>& shader)
 {
     auto scene = make_rc<Scene>();
+    scene->name = "Sponza";
 
     Entity sponza = load_obj("./assets/sponza/sponza.obj", shader);
     sponza.transform.position = {0.0f, -0.5f, 0.0f};
@@ -229,6 +234,7 @@ Rc<Scene> create_sponza_scene(const Rc<Shader>& shader)
 Rc<Scene> create_car_scene(const Rc<Shader>& shader)
 {
     auto scene = make_rc<Scene>();
+    scene->name = "Audi R8";
 
     scene->add_entity(load_obj("./assets/audi_r8/Audi_R8_2017.obj", shader));
 
@@ -239,13 +245,10 @@ Rc<Scene> create_car_scene(const Rc<Shader>& shader)
 Rc<Scene> create_backpack_scene(const Rc<Shader>& shader, const Rc<Mesh>& cube_mesh)
 {
     auto scene = make_rc<Scene>();
+    scene->name = "Backpack";
 
     scene->add_entity(load_obj("./assets/backpack/backpack.obj", shader, true));
-
+    scene->add_entity(create_floor(shader, cube_mesh, -2.5f));
-    Entity floor{cube_mesh, create_textured_material(shader, "./assets/textures/wall.jpg")};
-    floor.transform.position = {0.0f, -3.0f, 0.0f};
-    floor.transform.scale = {20.0f, 1.0f, 20.0f};
-    scene->add_entity(floor);
 
     add_random_lights(*scene, 4, 4, 37);
     return scene;
@@ -254,6 +257,8 @@ Rc<Scene> create_backpack_scene(const Rc<Shader>& shader, const Rc<Mesh>& cube_m
 Rc<Scene> create_cubes_scene(const Rc<Shader>& shader, const Rc<Mesh>& cube_mesh)
 {
     auto scene = make_rc<Scene>();
+    scene->name = "Cubes";
+
     auto material = create_textured_material(shader, "./assets/textures/container.jpg");
 
     const std::vector<glm::vec3> positions{
@@ -274,11 +279,88 @@ Rc<Scene> create_cubes_scene(const Rc<Shader>& shader, const Rc<Mesh>& cube_mesh
     return scene;
 }
 
-Rc<Material> create_textured_material(const Rc<Shader>& shader, const std::string& texture_path)
+// Containers resting on a floor, for testing specular maps: the steel frame
+// shines, the wood doesn't
+Rc<Scene> create_containers_scene(const Rc<Shader>& shader, const Rc<Mesh>& cube_mesh)
+{
+    auto scene = make_rc<Scene>();
+    scene->name = "Containers";
+
+    scene->add_entity(create_floor(shader, cube_mesh, -0.5f));
+
+    auto material = create_textured_material(shader, "./assets/textures/container2.png",
+                                             "./assets/textures/container2_specular.png");
+
+    struct Placement
+    {
+        glm::vec3 position; // Center of the container
+        float yaw_degrees;
+        float size;
+    };
+
+    // Unit containers on the floor have their center at y = 0
+    const std::vector<Placement> placements{
+        // Pyramid in the middle
+        {{-1.05f, 0.0f,  0.0f},   0.0f, 1.0f},
+        {{ 0.0f,  0.0f,  0.0f},   0.0f, 1.0f},
+        {{ 1.05f, 0.0f,  0.0f},   0.0f, 1.0f},
+        {{-0.56f, 1.0f,  0.0f},   4.0f, 1.0f},
+        {{ 0.56f, 1.0f,  0.0f},  -3.0f, 1.0f},
+        {{ 0.0f,  2.0f,  0.0f},  12.0f, 1.0f},
+
+        // Stack of two on the left
+        {{-3.2f,  0.0f, -0.5f},  15.0f, 1.0f},
+        {{-3.2f,  1.0f, -0.5f},  35.0f, 1.0f},
+
+        // Loose containers around
+        {{-3.0f,  0.0f,  2.0f}, -20.0f, 1.0f},
+        {{ 2.0f,  0.0f, -2.5f},  45.0f, 1.0f},
+        {{ 1.5f,  0.0f,  3.0f},  70.0f, 1.0f},
+
+        // A big one in the back
+        {{-3.5f,  0.5f, -3.5f},  25.0f, 2.0f},
+    };
+
+    for (const Placement& placement : placements) {
+        Entity container{cube_mesh, material};
+        container.transform.position = placement.position;
+        container.transform.set_rotation(glm::radians(placement.yaw_degrees), {0.0f, 1.0f, 0.0f});
+        container.transform.scale = glm::vec3(placement.size);
+        scene->add_entity(container);
+    }
+
+    // Only the local lights shine here, so their highlights are easy to see.
+    // The directional light's ambient stays to keep unlit sides from going black
+    DirectionalLight& sun = scene->light_environment.directional_light;
+    sun.diffuse = glm::vec3(0.0f);
+    sun.specular = glm::vec3(0.0f);
+
+    // More point lights than the other scenes, for more highlights to compare
+    add_random_lights(*scene, 8, 4, 2718);
+    return scene;
+}
+
+// 20x20 slab with the wall texture, its top surface at height top_y
+Entity create_floor(const Rc<Shader>& shader, const Rc<Mesh>& cube_mesh, float top_y)
+{
+    Entity floor{cube_mesh, create_textured_material(shader, "./assets/textures/wall.jpg")};
+    floor.transform.position = {0.0f, top_y - 0.5f, 0.0f};
+    floor.transform.scale = {20.0f, 1.0f, 20.0f};
+    return floor;
+}
+
+Rc<Material> create_textured_material(const Rc<Shader>& shader, const std::string& diffuse_path,
+                                      const std::string& specular_path/* = ""*/)
 {
     auto material = make_rc<Material>();
     material->shader = shader;
-    material->diffuse_map = ResourceCache::load_texture(texture_path);
+    material->diffuse_map = ResourceCache::load_texture(diffuse_path);
+
+    // Optional, like in the OBJ loader: without it specular_color is used alone
+    if (!specular_path.empty()) {
+        material->specular_map = ResourceCache::load_texture(specular_path, false);
+    }
+
     return material;
 }
 
@@ -468,11 +550,21 @@ void draw_panel_window(AppState& app)
     ImGui::SeparatorText("Scene Selector");
 
     for (size_t i = 0; i < app.scenes.size(); ++i) {
+        const std::string& name = app.scenes[i]->name;
+
         char label[64];
+        if (name.empty()) {
             ImFormatString(label, IM_ARRAYSIZE(label), "Scene %zu", i);
+        } else {
+            ImFormatString(label, IM_ARRAYSIZE(label), "%s", name.c_str());
+        }
+
+        // ImGui identifies widgets by label, the index keeps equal names apart
+        ImGui::PushID(static_cast<int>(i));
         if (ImGui::RadioButton(label, app.selected_scene_index == i)) {
             app.selected_scene_index = i;
         }
+        ImGui::PopID();
     }
 
     ImGui::SeparatorText("Camera Settings");

src/scene.hpp

@@ -1,6 +1,7 @@
 #ifndef FAN_SCENE_HPP_
 #define FAN_SCENE_HPP_
 
+#include <string>
 #include <vector>
 
 #include "entity.hpp"
@@ -12,6 +13,7 @@ namespace Fan
 class Scene
 {
 public:
+    std::string name{};
     LightEnvironment light_environment{};
 
     // Stores a copy: later changes to the passed Entity don't affect the scene.