text: //
  // Copyright (c) 2008-2022 the Urho3D project.
  //
  // Permission is hereby granted, free of charge, to any person obtaining a copy
  // of this software and associated documentation files (the "Software"), to deal
  // in the Software without restriction, including without limitation the rights
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  // copies of the Software, and to permit persons to whom the Software is
  // furnished to do so, subject to the following conditions:
  //
  // The above copyright notice and this permission notice shall be included in
  // all copies or substantial portions of the Software.
  //
  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  // THE SOFTWARE.
  //
  
  #include <Urho3D/Core/CoreEvents.h>
  #include <Urho3D/Engine/Engine.h>
  #include <Urho3D/Graphics/Camera.h>
  #include <Urho3D/Graphics/DebugRenderer.h>
  #include <Urho3D/Graphics/Graphics.h>
  #include <Urho3D/Graphics/Light.h>
  #include <Urho3D/Graphics/Material.h>
  #include <Urho3D/Graphics/Model.h>
  #include <Urho3D/Graphics/Octree.h>
  #include <Urho3D/Graphics/Renderer.h>
  #include <Urho3D/Graphics/StaticModel.h>
  #include <Urho3D/Graphics/Zone.h>
  #include <Urho3D/Input/Input.h>
  #include <Urho3D/IO/File.h>
  #include <Urho3D/IO/FileSystem.h>
  #include <Urho3D/Physics/CollisionShape.h>
  #include <Urho3D/Physics/PhysicsWorld.h>
  #include <Urho3D/Physics/RigidBody.h>
  #include <Urho3D/Resource/ResourceCache.h>
  #include <Urho3D/Scene/Scene.h>
  #include <Urho3D/UI/Font.h>
  #include <Urho3D/UI/Text.h>
  #include <Urho3D/UI/UI.h>
  
  #include "PhysicsStressTest.h"
  
  #include <Urho3D/DebugNew.h>
  
  
  PhysicsStressTest::PhysicsStressTest(Context* context) :
      Sample(context),
      drawDebug_(false)
  {
  }
  
  void PhysicsStressTest::Start()
  {
      // Execute base class startup
      Sample::Start();
  
      // Create the scene content
      CreateScene();
  
      // Create the UI content
      CreateInstructions();
  
      // Setup the viewport for displaying the scene
      SetupViewport();
  
      // Hook up to the frame update and render post-update events
      SubscribeToEvents();
  
      // Set the mouse mode to use in the sample
      Sample::InitMouseMode(MM_RELATIVE);
  }
  
  void PhysicsStressTest::CreateScene()
  {
      auto* cache = GetSubsystem<ResourceCache>();
  
      scene_ = new Scene(context_);
  
      // Create octree, use default volume (-1000, -1000, -1000) to (1000, 1000, 1000)
      // Create a physics simulation world with default parameters, which will update at 60fps. Like the Octree must
      // exist before creating drawable components, the PhysicsWorld must exist before creating physics components.
      // Finally, create a DebugRenderer component so that we can draw physics debug geometry
      scene_->CreateComponent<Octree>();
      scene_->CreateComponent<PhysicsWorld>();
      scene_->CreateComponent<DebugRenderer>();
  
      // Create a Zone component for ambient lighting & fog control
      Node* zoneNode = scene_->CreateChild("Zone");
      auto* zone = zoneNode->CreateComponent<Zone>();
      zone->SetBoundingBox(BoundingBox(-1000.0f, 1000.0f));
      zone->SetAmbientColor(Color(0.15f, 0.15f, 0.15f));
      zone->SetFogColor(Color(0.5f, 0.5f, 0.7f));
      zone->SetFogStart(100.0f);
      zone->SetFogEnd(300.0f);
  
      // Create a directional light to the world. Enable cascaded shadows on it
      Node* lightNode = scene_->CreateChild("DirectionalLight");
      lightNode->SetDirection(Vector3(0.6f, -1.0f, 0.8f));
      auto* light = lightNode->CreateComponent<Light>();
      light->SetLightType(LIGHT_DIRECTIONAL);
      light->SetCastShadows(true);
      light->SetShadowBias(BiasParameters(0.00025f, 0.5f));
      // Set cascade splits at 10, 50 and 200 world units, fade shadows out at 80% of maximum shadow distance
      light->SetShadowCascade(CascadeParameters(10.0f, 50.0f, 200.0f, 0.0f, 0.8f));
  
      {
          // Create a floor object, 500 x 500 world units. Adjust position so that the ground is at zero Y
          Node* floorNode = scene_->CreateChild("Floor");
          floorNode->SetPosition(Vector3(0.0f, -0.5f, 0.0f));
          floorNode->SetScale(Vector3(500.0f, 1.0f, 500.0f));
          auto* floorObject = floorNode->CreateComponent<StaticModel>();
          floorObject->SetModel(cache->GetResource<Model>("Models/Box.mdl"));
          floorObject->SetMaterial(cache->GetResource<Material>("Materials/StoneTiled.xml"));
  
          // Make the floor physical by adding RigidBody and CollisionShape components
          /*RigidBody* body = */floorNode->CreateComponent<RigidBody>();
          auto* shape = floorNode->CreateComponent<CollisionShape>();
          shape->SetBox(Vector3::ONE);
      }
  
      {
          // Create static mushrooms with triangle mesh collision
          const unsigned NUM_MUSHROOMS = 50;
          for (unsigned i = 0; i < NUM_MUSHROOMS; ++i)
          {
              Node* mushroomNode = scene_->CreateChild("Mushroom");
              mushroomNode->SetPosition(Vector3(Random(400.0f) - 200.0f, 0.0f, Random(400.0f) - 200.0f));
              mushroomNode->SetRotation(Quaternion(0.0f, Random(360.0f), 0.0f));
              mushroomNode->SetScale(5.0f + Random(5.0f));
              auto* mushroomObject = mushroomNode->CreateComponent<StaticModel>();
              mushroomObject->SetModel(cache->GetResource<Model>("Models/Mushroom.mdl"));
              mushroomObject->SetMaterial(cache->GetResource<Material>("Materials/Mushroom.xml"));
              mushroomObject->SetCastShadows(true);
  
              /*RigidBody* body = */mushroomNode->CreateComponent<RigidBody>();
              auto* shape = mushroomNode->CreateComponent<CollisionShape>();
              // By default the highest LOD level will be used, the LOD level can be passed as an optional parameter
              shape->SetTriangleMesh(mushroomObject->GetModel());
          }
      }
  
      {
          // Create a large amount of falling physics objects
          const unsigned NUM_OBJECTS = 1000;
          for (unsigned i = 0; i < NUM_OBJECTS; ++i)
          {
              Node* boxNode = scene_->CreateChild("Box");
              boxNode->SetPosition(Vector3(0.0f, i * 2.0f + 100.0f, 0.0f));
              auto* boxObject = boxNode->CreateComponent<StaticModel>();
              boxObject->SetModel(cache->GetResource<Model>("Models/Box.mdl"));
              boxObject->SetMaterial(cache->GetResource<Material>("Materials/StoneSmall.xml"));
              boxObject->SetCastShadows(true);
  
              // Give the RigidBody mass to make it movable and also adjust friction
              auto* body = boxNode->CreateComponent<RigidBody>();
              body->SetMass(1.0f);
              body->SetFriction(1.0f);
              // Disable collision event signaling to reduce CPU load of the physics simulation
              body->SetCollisionEventMode(COLLISION_NEVER);
              auto* shape = boxNode->CreateComponent<CollisionShape>();
              shape->SetBox(Vector3::ONE);
          }
      }
  
      // Create the camera. Limit far clip distance to match the fog. Note: now we actually create the camera node outside
      // the scene, because we want it to be unaffected by scene load / save
      cameraNode_ = new Node(context_);
      auto* camera = cameraNode_->CreateComponent<Camera>();
      camera->SetFarClip(300.0f);
  
      // Set an initial position for the camera scene node above the floor
      cameraNode_->SetPosition(Vector3(0.0f, 3.0f, -20.0f));
  }
  
  void PhysicsStressTest::CreateInstructions()
  {
      auto* cache = GetSubsystem<ResourceCache>();
      auto* ui = GetSubsystem<UI>();
  
      // Construct new Text object, set string to display and font to use
      auto* instructionText = ui->GetRoot()->CreateChild<Text>();
      instructionText->SetText(
          "Use WASD keys and mouse/touch to move\n"
          "LMB to spawn physics objects\n"
          "F5 to save scene, F7 to load\n"
          "Space to toggle physics debug geometry"
      );
      instructionText->SetFont(cache->GetResource<Font>("Fonts/Anonymous Pro.ttf"), 15);
      // The text has multiple rows. Center them in relation to each other
      instructionText->SetTextAlignment(HA_CENTER);
  
      // Position the text relative to the screen center
      instructionText->SetHorizontalAlignment(HA_CENTER);
      instructionText->SetVerticalAlignment(VA_CENTER);
      instructionText->SetPosition(0, ui->GetRoot()->GetHeight() / 4);
  }
  
  void PhysicsStressTest::SetupViewport()
  {
      auto* renderer = GetSubsystem<Renderer>();
  
      // Set up a viewport to the Renderer subsystem so that the 3D scene can be seen
      SharedPtr<Viewport> viewport(new Viewport(context_, scene_, cameraNode_->GetComponent<Camera>()));
      renderer->SetViewport(0, viewport);
  }
  
  void PhysicsStressTest::SubscribeToEvents()
  {
      // Subscribe HandleUpdate() function for processing update events
      SubscribeToEvent(E_UPDATE, URHO3D_HANDLER(PhysicsStressTest, HandleUpdate));
  
      // Subscribe HandlePostRenderUpdate() function for processing the post-render update event, during which we request
      // debug geometry
      SubscribeToEvent(E_POSTRENDERUPDATE, URHO3D_HANDLER(PhysicsStressTest, HandlePostRenderUpdate));
  }
  
  void PhysicsStressTest::MoveCamera(float timeStep)
  {
      // Do not move if the UI has a focused element (the console)
      if (GetSubsystem<UI>()->GetFocusElement())
          return;
  
      auto* input = GetSubsystem<Input>();
  
      // Movement speed as world units per second
      const float MOVE_SPEED = 20.0f;
      // Mouse sensitivity as degrees per pixel
      const float MOUSE_SENSITIVITY = 0.1f;
  
      // Use this frame's mouse motion to adjust camera node yaw and pitch. Clamp the pitch between -90 and 90 degrees
      IntVector2 mouseMove = input->GetMouseMove();
      yaw_ += MOUSE_SENSITIVITY * mouseMove.x_;
      pitch_ += MOUSE_SENSITIVITY * mouseMove.y_;
      pitch_ = Clamp(pitch_, -90.0f, 90.0f);
  
      // Construct new orientation for the camera scene node from yaw and pitch. Roll is fixed to zero
      cameraNode_->SetRotation(Quaternion(pitch_, yaw_, 0.0f));
  
      // Read WASD keys and move the camera scene node to the corresponding direction if they are pressed
      if (input->GetKeyDown(KEY_W))
          cameraNode_->Translate(Vector3::FORWARD * MOVE_SPEED * timeStep);
      if (input->GetKeyDown(KEY_S))
          cameraNode_->Translate(Vector3::BACK * MOVE_SPEED * timeStep);
      if (input->GetKeyDown(KEY_A))
          cameraNode_->Translate(Vector3::LEFT * MOVE_SPEED * timeStep);
      if (input->GetKeyDown(KEY_D))
          cameraNode_->Translate(Vector3::RIGHT * MOVE_SPEED * timeStep);
  
      // "Shoot" a physics object with left mousebutton
      if (input->GetMouseButtonPress(MOUSEB_LEFT))
          SpawnObject();
  
      // Check for loading / saving the scene
      if (input->GetKeyPress(KEY_F5))
      {
          File saveFile(context_, GetSubsystem<FileSystem>()->GetProgramDir() + "Data/Scenes/PhysicsStressTest.xml", FILE_WRITE);
          scene_->SaveXML(saveFile);
      }
      if (input->GetKeyPress(KEY_F7))
      {
          File loadFile(context_, GetSubsystem<FileSystem>()->GetProgramDir() + "Data/Scenes/PhysicsStressTest.xml", FILE_READ);
          scene_->LoadXML(loadFile);
      }
  
      // Toggle physics debug geometry with space
      if (input->GetKeyPress(KEY_SPACE))
          drawDebug_ = !drawDebug_;
  }
  
  void PhysicsStressTest::SpawnObject()
  {
      auto* cache = GetSubsystem<ResourceCache>();
  
      // Create a smaller box at camera position
      Node* boxNode = scene_->CreateChild("SmallBox");
      boxNode->SetPosition(cameraNode_->GetPosition());
      boxNode->SetRotation(cameraNode_->GetRotation());
      boxNode->SetScale(0.25f);
      auto* boxObject = boxNode->CreateComponent<StaticModel>();
      boxObject->SetModel(cache->GetResource<Model>("Models/Box.mdl"));
      boxObject->SetMaterial(cache->GetResource<Material>("Materials/StoneSmall.xml"));
      boxObject->SetCastShadows(true);
  
      // Create physics components, use a smaller mass also
      auto* body = boxNode->CreateComponent<RigidBody>();
      body->SetMass(0.25f);
      body->SetFriction(0.75f);
      auto* shape = boxNode->CreateComponent<CollisionShape>();
      shape->SetBox(Vector3::ONE);
  
      const float OBJECT_VELOCITY = 10.0f;
  
      // Set initial velocity for the RigidBody based on camera forward vector. Add also a slight up component
      // to overcome gravity better
      body->SetLinearVelocity(cameraNode_->GetRotation() * Vector3(0.0f, 0.25f, 1.0f) * OBJECT_VELOCITY);
  }
  
  void PhysicsStressTest::HandleUpdate(StringHash eventType, VariantMap& eventData)
  {
      using namespace Update;
  
      // Take the frame time step, which is stored as a float
      float timeStep = eventData[P_TIMESTEP].GetFloat();
  
      // Move the camera, scale movement with time step
      MoveCamera(timeStep);
  }
  
  void PhysicsStressTest::HandlePostRenderUpdate(StringHash eventType, VariantMap& eventData)
  {
      // If draw debug mode is enabled, draw physics debug geometry. Use depth test to make the result easier to interpret
      if (drawDebug_)
          scene_->GetComponent<PhysicsWorld>()->DrawDebugGeometry(true);
  }
  