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Managing Game Rules

Let's create the LevelManager component to manage game rules, level states and the User Interface. The manager creates a graphical user interface and shows the time left until the game is over. It also checks and shows the number of objects left to clear away from the Play Area.

Step 1. Set Up Timer and Game UI#

A node with the LevelManager component assigned should be present in the world for rules to take effect. It will manage the timer and update the widget user interface for the game.

  1. Create a new C++ component and call it LevelManager.
  2. Write the following code in an IDE and save the solution. Build and run the solution to generate a property file for the component.
    Notice
    Take note that the LevelManager component's init() method is set to be called in the 2nd order to make sure it is initialized after the ObjectGenerator component which creates and parents all physical objects to it (ObjectGenerator's initialization order is set to 1st).
    LevelManager.h (С++)
    #pragma once
    #include <UnigineComponentSystem.h>
    
    #include <UnigineWidgets.h>
    #include <UnigineGame.h>
    #include <UnigineString.h>
    
    class LevelManager : public Unigine::ComponentBase
    {
    public:
    	// declare constructor and destructor for our class and define a property name. 
    	COMPONENT_DEFINE(LevelManager, ComponentBase)
    	// declare methods to be called at the corresponding stages of the execution sequence
    	COMPONENT_INIT(init, 2); // 2nd initialization order
    	COMPONENT_UPDATE(update);
    	COMPONENT_SHUTDOWN(shutdown);
    	// level timer
    	PROP_PARAM(Float, timer, 100.0f);
    
    	void decPhysicalObjectsNum();
    	void setEndGameCallback(Unigine::CallbackBase *callback) { endGameEvent = callback; }
    
    protected:
    	void init();
    	void update();
    	void shutdown();
    
    	void initGUI();
    
    private:
    	Unigine::CallbackBase *endGameEvent = nullptr;
    
    	bool isCounting = true;
    
    	int physicalObjectsNum;
    
    	Unigine::WidgetLabelPtr widget_timer, widget_goal;
    
    	Unigine::ObjectTextPtr endText;
    };
    LevelManager.cpp (С++)
    #include "LevelManager.h"
    
    using namespace Unigine;
    using namespace Math;
    
    REGISTER_COMPONENT(LevelManager);
    
    void LevelManager::init()
    {
    	LevelManager::initGUI();
    
    	// find the object text node of the widget
    	endText = checked_ptr_cast<ObjectText>(Game::getPlayer()->findNode("header_text", 1)); //check again
    
    	// count dynamic objects in the level
    	physicalObjectsNum = node->getNumChildren();
    }
    
    void LevelManager::initGUI()
    {
    	// get a GUI pointer
    	GuiPtr gui = Gui::get();
    
    	// create a label widget and set up its parameters
    	widget_timer = WidgetLabel::create(gui, "Time Left:");
    	widget_timer->setPosition(10, 10);
    	widget_timer->setFontColor(vec4::RED);
    
    	widget_goal = WidgetLabel::create(gui, "Objects Left: ");
    	widget_goal->setPosition(10, 30);
    	widget_goal->setFontColor(vec4::BLUE);
    
    	// add widgets to the GUI
    	gui->addChild(widget_timer, Gui::ALIGN_OVERLAP);
    	gui->addChild(widget_goal, Gui::ALIGN_OVERLAP);
    }
    
    void LevelManager::update()
    {
    	// decrease the timer
    	if (isCounting)
    	{
    		timer = timer - Game::getIFps();
    		if (timer <= 0)
    		{
    			//set end game text
    			endText->setText("Game Over");
    			if (endGameEvent) endGameEvent->run();
    			isCounting = false;
    		}
    	}
    
    	//win
    	if (physicalObjectsNum <= 0)
    	{
    		endText->setText("Success!");
    		if (endGameEvent) endGameEvent->run();
    		isCounting = false;
    	}
    
    	// show the current time and objects left to clear
    	if (isCounting)
    	{
    		widget_timer->setText(String::format("Time Left: %.2f s", timer.get()));
    		widget_goal->setText((String)"Objects Left: " + String::itoa(physicalObjectsNum, 10));
    	}
    	//hide the widgets on endgame
    	else
    	{
    		widget_timer->setEnabled(false);
    		widget_goal->setEnabled(false);
    	}
    }
    
    void LevelManager::shutdown()
    {
    	widget_timer->deleteLater();
    	widget_goal->deleteLater();
    }
    
    void LevelManager::decPhysicalObjectsNum()
    {
    	physicalObjectsNum--;
    }
  3. Create a new Dummy Node called level_manager and place it somewhere in the world.
  4. Add a LevelManager component to the level_manager node via the Parameters window in the UnigineEditor.

We created the system GUI via the API from the code. The alternative method is to use UI files.

Step 2. Detect Physical Objects#

Only the level_manager's children nodes shall be deleted by the Kill Zone's trigger. Let's add each physical object as a child to the level_manager node. For the rules to function properly you also need to add a new condition and a method call to the KillZone component that checks if the entered node has a parent with the LevelManager component attached.

  1. Open the KillZone component in your IDE, add a levelManager field and replace the content of the Enter callback function according to the following code.
    KillZone.h (C++)
    #pragma once
    #include <UnigineComponentSystem.h>
    
    #include <UnigineWorlds.h>
    #include "LevelManager.h"
    
    class KillZone : public Unigine::ComponentBase
    {
    public:
    	// declare constructor and destructor for our class and define a property name. 
    	COMPONENT_DEFINE(KillZone, ComponentBase)
    	// declare methods to be called at the corresponding stages of the execution sequence
    	COMPONENT_INIT(init);
    
    protected:
    	void init();
    	
    	void enterCallback(Unigine::NodePtr target);
    
    private:
    	// the area into which an object should fall
    	Unigine::WorldTriggerPtr trigger;
    
    //========================== NEW - BEGIN ===============================
    	LevelManager *levelManager;
    //=========================== NEW - END ================================	
    };
    KillZone.cpp (C++)
    #include "KillZone.h"
    
    using namespace Unigine;
    
    REGISTER_COMPONENT(KillZone);
    
    void KillZone::init()
    {
    	trigger = checked_ptr_cast<WorldTrigger>(node);
    
    	// set the callback to be executed when an object enters the area
    	if (trigger)
    		trigger->addEnterCallback(MakeCallback(this, &KillZone::enterCallback));
    }
    
    //========================== NEW - BEGIN ===============================
    void KillZone::enterCallback(NodePtr target)
    {
    	levelManager = getComponentInParent<LevelManager>(target);
    	// check if the parent node has a LevelManager component attached
    	if (levelManager)
    	{
    		// delete the entered node and decrease the amount of physical objects
    		levelManager->decPhysicalObjectsNum();
    		target->deleteLater();
    	}
    }
    //=========================== NEW - END ================================
  2. Let's set the level_manager node as a parent to physical objects. Open the ObjectGenerator component in your IDE and replace the code in the corresponding files with the following. Save the code in your IDE and switch back to UnigineEditor.
    ObjectGenerator.h (C++)
    #include <UnigineComponentSystem.h>
    #include <UnigineGame.h>
    
    #pragma once
    class ObjectGenerator : public Unigine::ComponentBase
    {
    
    public:
    	COMPONENT_DEFINE(ObjectGenerator, ComponentBase);
    	COMPONENT_INIT(init, 1);
    
    //========================== NEW - BEGIN ===============================
    	PROP_PARAM(Node, levelManager);
    //=========================== NEW - END ================================
    
    protected:
    	void init();
    };
    ObjectGenerator.cpp (C++)
    #include "ObjectGenerator.h"
    
    using namespace Unigine;
    
    REGISTER_COMPONENT(ObjectGenerator);
    
    void ObjectGenerator::init()
    {
    //========================== NEW - BEGIN ===============================
    	if (levelManager)
    	{
    //=========================== NEW - END ================================	
    		// cube 
    		MeshPtr meshBox = Mesh::create();
    		meshBox->addBoxSurface("box_surface", Math::vec3(1.0f));
    		ObjectMeshStaticPtr box = ObjectMeshStatic::create(meshBox);
    		//========================== NEW - BEGIN ===============================
    		box->setParent(levelManager);
    		//========================== NEW - END ===============================
    		box->setTriggerInteractionEnabled(1);
    		box->setIntersectionMask(0x00000080, meshBox->findSurface("box_surface")); // check the BulletIntersection bit
    		box->setWorldTransform(translate(Math::Vec3(0.5f, 7.5f, 1.0f)));
    		box->setMaterial("mesh_base_0", "*");
    		box->setName("box");
    		Unigine::BodyRigidPtr bodyBox = BodyRigid::create(box);
    		ShapeBoxPtr shapeBox = ShapeBox::create(bodyBox, Math::vec3(1.0f));
    		ShapeSphere::create(bodyBox, 0.5f);
    		bodyBox->setShapeBased(0);
    		bodyBox->setMass(2.0f);
    
    		// sphere
    		MeshPtr meshShpere = Mesh::create();
    		meshShpere->addSphereSurface("sphere_surface", 0.5f, 9, 32);
    		ObjectMeshStaticPtr sphere = ObjectMeshStatic::create(meshShpere);
    		//========================== NEW - BEGIN ===============================
    		sphere->setParent(levelManager);
    		//========================== NEW - END ===============================
    		sphere->setTriggerInteractionEnabled(1);
    		sphere->setIntersectionMask(0x00000080, meshShpere->findSurface("sphere_surface")); // check the BulletIntersection bit
    		sphere->setWorldTransform(translate(Math::Vec3(4.5f, 5.5f, 1.0f)));
    		sphere->setMaterial("mesh_base_1", "*");
    		sphere->setName("sphere");
    		BodyRigidPtr bodySphere = BodyRigid::create(sphere);
    		ShapeSphere::create(bodySphere, 0.5f);
    		bodySphere->setShapeBased(0);
    		bodySphere->setMass(2.0f);
    
    		// capsule
    		MeshPtr meshCapsule = Mesh::create();
    		meshCapsule->addCapsuleSurface("capsule_surface", 0.5f, 1.0f, 9, 32);
    		ObjectMeshStaticPtr capsule = ObjectMeshStatic::create(meshCapsule);
    		//========================== NEW - BEGIN ===============================
    		capsule->setParent(levelManager);
    		//========================== NEW - END ===============================
    		capsule->setTriggerInteractionEnabled(1);
    		capsule->setIntersectionMask(0x00000080, meshCapsule->findSurface("capsule_surface")); // check the BulletIntersection bit
    		capsule->setWorldTransform(translate(Math::Vec3(4.5f, 0.5f, 3.0f)));
    		capsule->setMaterial("mesh_base_2", "*");
    		capsule->setName("capsule");
    		BodyRigidPtr bodyCapsule = BodyRigid::create(capsule);
    		ShapeCapsule::create(bodyCapsule, 0.5f, 1.0f);
    		bodyCapsule->setShapeBased(0);
    		bodyCapsule->setMass(2.0f);
    //========================== NEW - BEGIN ===============================
    	}
    //=========================== NEW - END ================================
    }
  3. Select the object_generator node in the World Nodes window and drag the level_manager node to the corresponding field of the ObjectGenerator property.
  4. Save changes to the world. Go to File->Save World or press Ctrl+S hotkey.
  5. Switch to your IDE. Save changes to the solution and then build and run the game to see the game rules in action.
Last update: 2021-08-24
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