C# in Unity 101. Objects perform operations when receiving a request/message from a client

Transcription

1 C# in Unity 101 OOP What is OOP? Objects perform operations when receiving a request/message from a client Requests are the ONLY* way to get an object to execute an operation or change the object s internal data This means an object s internal state is encapsulated (invisible from outside the object) Stats playerstats = new Stats( 10, 10 ) playerstats.getpower() playerstats.gettoughness() (We don t always adhere to this rule for performance reasons ) 1

2 OOP Why use Object Oriented Programming? Encapsulate a variety of variables and methods into a single package Reuse existing functionality or override it! Variables have names, helping humans remember what they mean Restrictions can be imposed to stop inappropriate use Allows for programming that emulates reality OOP What Is Difficult About OOP? Decomposing a system into objects During decomposition we will think about: Encapsulation Granularity Dependency Flexibility Performance Evolution Reusability While there are design patterns to help us, many situations call for different strategies (and that is where it gets complex!) 2

3 OOP A class is a data type / object type A class is a template (blueprint) used to create objects Classes are abstract models for ideas or concepts Describes how to package data and procedures this.color this.maxspeed this.efficiency start() steer( angle) OOP An instance is an object generated from a class A class is just a definition To use a class, you need to create an instance! A class = blueprint, an instance = actual car 3

4 OOP Instance attributes are UNIQUE to the instance Each instance of a car has separate values (DEFAULT) this.color = null this.maxspeed = 0 this.efficiency = 0 this.color = Blue this.maxspeed = 65 this.efficiency = 48 this.color = Red this.maxspeed = 150 this.efficiency = 12 this.color = Black this.maxspeed = 80 this.efficiency = 24 this.color = Green this.maxspeed = 200 this.efficiency = 8 OOP When we write a class we are DEFINING a class We have not created an instance of the class We have instructed C# how to create the class We are telling C# what variables a car is composed of and what methods it has 4

5 OOP - Inheritance Inheritance allows for code reuse A class can be built off of an existing class to add additional functionality without rewriting all the previous methods and attributes A child class can also override previous functionality The following slides are an example for using inheritance: OOP - Inheritance Example Lets create a class to represent different NPC or player characters in a game: Lets start with the most general thing we can think of: An entity - something that exists in 3D space Entity will be a base class for classes needing a physical location A entity has attributes (member variables): string name Vector3 position Entity name position 5

6 OOP - Inheritance Example Entity is very simple If we want a new, more complex type of Entity we can reuse Entity When designing classes, we try to group common attributes together into base classes Entity name position This allows us to build upon previously developed code We do this through inheritance Something that is an Entity but more OOP - Inheritance Example A Human is an Entity It contains everything that an Entity is + more Human adds: hitpoints power toughness item int GetPower() int GetToughness() void SwapItem(item) bool IsAlive() Base Class Super Class Parent Class Entity Human Derived Class Sub Class Child Class Human Entity name position hitpoints power toughness item GetPower() GetToughness() SwapItem() IsAlive() 6

7 OOP Inheritence Entity Human Item Zombie The Bubble-Up Effect (Monolithic Classes) Too much inheritance can be a bad thing! Original Unreal Tournament had a monolithic class hierarchy The desire to share features across dissimilar classes causes features to bubble up the hierarchy Actor Brush Controller AIController PlayerController Info Light Inventory Ammunition Powerups Weapon Example: The desire to allow objects to float on water Eventually, flotation becomes a fundamental property of everything GameInfo HUD Pawn From: Game Engine Architecture Vehicle UnrealPawn 7

8 The Deadly Diamond Multiple Inheritance - inherit from more than one class C# does not allow you to do this because of what is called the DIAMOND OF DEATH, where multiple copies of vehicle could be initialized Vehicle LandVehicle WaterVehicle AmphibiousVehicle From: Game Engine Architecture C# Versions C# was first released in 2002 and has changed greatly over the years For Unity and in general, we ll be working with C# 3.0 / 3.5 This means all the latest features of the language might not be available, so be careful if you take C# tutorials 8

9 C# Monobehavior When working inside of Unity we write scripts, not programs Unity will handle compiling and building our project by assembling its code with our scripts We do not have a Main point of entry, the game engine handles all of that C# Monobehavior All scripts in Unity derive from MonoBehavior MonoBehavior s come with methods that provide you with important times in the game engine s cycle to perform actions: Awake() When the script instance is being loaded Start() Called when the script is enabled before any updates occur Update() Called every frame if enabled FixedUpdate() Fixed framerate frame update, good for physics LateUpdate() Called every frame after all updates occur OnDisable() Called when disabled OnEnable() Called when enabled OnTriggerEnter() OnTriggerExit() 9

10 C# Class Structure C# Variables All of your favorite variable types make an appearance in C#: All of these variable names are actually aliases for.net types stored as structures in namespace System byte System.Byte sbyte System.byteSByte int System.Int32 uint System.UInt32 short System.Int16 ushort System.UInt16 long System.Int64 ulong System.UInt64 float System.Single double System.Double char System.Char bool System.Boolean object System.Object string System.String decimal System.Decimal DateTime System. DateTime 10

11 C# Variables Arrays are handled using square brackets float[] myarray = {1.0f, 2.0f}; float[] mysecondarray = new float[2]; float[] mythirdarray = new float[2] {1.0f, 2.0f}; int[,] my2darray = new int[2,2]; C# Value vs. Reference Most standard types are pass by value (they hold their actual value in its own memory space) When passing a value through a method, copies are created and changes don t persist when the method ends A reference type holds a pointer to a memory location where the value is stored Class by references include String, arrays, classes, and delegates Changes inside a method to a reference type will persist after the method ends By default all reference values have the type of null, meaning they are not pointing to any memory address 11

12 C# Interfaces Interfaces are not to be confused with classes, they contain declarations of methods & properties but not the implementation Interfaces are usually prefaced with the letter I: Interfaces allow you to extend and work with existing code by enforcing a set of methods that are needed to make it work Two difference classes can implement the same interface and be stored in the same array of that type class TestClass : InterfaceOne, InterfaceTwo, InterfaceThree{} C# Abstract Class Allows you to write in functionality that can be implemented or overridden It is an incomplete class that must be finished before it can be used abstract class ShapesClass{ abstract public int Area(); } class Square : ShapesClass { int side = 0; public Square(int n) { side = n; } public override int Area() { return side * side; } } Can use One Abstract Class, but Many Interfaces 12

13 C# Virtual & Base Keyword The virtual keyword allows child classes to override a method or property It is used in tandem with the keyword override in the child class, indicating that it is replacing the method The keyword base allows us to call the parent classes methods / constructors if we have overridden it public class Person { protected string ssn = " "; protected string name = "John L. Malgraine"; public virtual void GetInfo() { Console.WriteLine("Name: {0}", name); Console.WriteLine("SSN: {0}", ssn);}} class Employee : Person { public string id = "ABC567EFG"; public override void GetInfo(){ base.getinfo(); Console.WriteLine("Employee ID: {0}", id); } } C# Conditionals if(boolean expression){} else if(boolean expression){} else {} Boolean Expression? First : Second switch(expression) { case value1: break; case value2: break; default: break; } 13

14 C# For Loops for(int i = 0; i < somesize; i++) { do work } public class IterateSpanExample { { Span<int> numbers = new int[] { 3, 14, 15, 92, 6 }; foreach (int number in numbers) { Debug.Log(number.ToString()); } } while(boolean expression) {} C# Try Catch try { }...do something that might throw an error catch(exception e) { } 14

15 C# Methods Methods include access level, return type and parameters You are allowed to overload methods (same name different number of parameters) Methods can be declared as static so that an instance of the class does not need to exist: public static int GetInt() {return myinteger;} C# Delegates & Events Think of a delegate as a function pointer They are created using the keyword delegate with the signature of the method afterwards A delegate is able to hold a method and can use it to be called later It is the first part in creating Events, which fire off at the correct time public delegate int DelegateName(int x, float y) 15

16 C# Delegates & Events Events work with delegates to fire off when something important happens An event will notify everyone who is subscribed public event delegatetype InputRecieved; protected void OnInputReceived(){ if(inputreceived!= null) InputReceived();} void Update() { if(controllerinput.getbuttondown) OnInputReceived(); } C# Delegates & Events We can add and subtract methods to the event using the += and -= operators When the times comes, OnInputReceived calls the Event and everyone who has subscribed gets their method called Player OnInputReceived Movement Recorder Menu System 16

17 IEnumerators We may wish to wait a set amount of time before performing an action, or fire off some action and have it progress at a desired rate We can use Coroutines and methods that return IEnumerator objects to control execution based on time StartCoroutine( WaitForTime ); IEnumerator WaitForTime() { yield return new WaitForSeconds(5.0f); } Play/Pause Scene Hierarchy Scene View Inspector Project View 17

18 Play/Pause Scene Hierarchy Scene View Inspector Project View We can move around our scene using the following: Arrow keys on a keyboard Pan Middle Mouse Button Rotate Camera Right Mouse Button Rotate About Focus Point Alt + Left Mouse Button Zoom In / Out Alt + Right Mouse Button F Key Focus on selected object 18

19 Our Hierarchy shows all the Game Objects in our scene We always start with a Main Camera and a Directional Light We can add additional Game Objects by Right Clicking in the window and selecting To move Game Objects around select one and a gizmo will appear This gizmo can be one of 3 types, for: Translate Rotate RGB = XYZ Scale 19

20 We can also create Game Objects by going under the GameObject menu at the top left of our Unity Window GameObjects aren t always created at the (0,0,0) position, but instead where the camera is looking We can use the inspector to see the position, rotation and scale of the object as well as reset it Objects selected in the Hierarchy panel will have their information displayed in the Inspector panel All Game Objects have a Transform component on top We can reset the transform component by typing manually or by pressing the gear and selecting reset 20

21 Two Game Objects differ from one another by having different components attached Select the Main Camera object from the hierarchy Notice that a Light has a Light component and a Camera has a Camera and an Audio Listener component ( to hear sounds with ) We do not need to rely on the GameObjects already supplied by Unity, we can build our own from a blank Game Object Right Click in the Hierarchy and create an Empty Game Object Note it has only a Transform Component and nothing else Click the Add Component button and type in Light in the search field Press enter and now your Game Object acts just like a Light 21

22 We can add lots of components to objects to give them various abilities Select a Game Object in the hierarchy and instead of using the Add Component button use the Component drop down menu at the upper right of the Unity window Try adding random components just to get used to working with them To add our own functionality to Unity, we need to create C# scripts, which are components we can attach to game objects Right Click on your project directory and create a new folder and name it Scripts Inside the folder right click and create a script called Pulse Double-click the script to open it in your chosen editor (usually Visual Studio) 22

23 Unity will automatically include 3 very useful namespaces into your script: System.Collections System.Collections.Generic UnityEngine All scripts that are components inherit from the class MonoBehavior It will also automatically add the Start method and the Update method, which get called by Unity at the appropriate time automatically We are going to make a Sphere Game Object scale up and down (Pulse) over time Create a Sphere Game Object in your hierarchy using one of the methods specified Select the sphere to see it in the inspector Select the Pulse script in your Project window and drag it over the empty portion of the inspector at the bottom to add it as a component of the sphere 23

24 Next we will alternate the colors of the sphere by manipulating the material of the object Create a new material by right clicking in your project and selecting new material, name it Sphere Drag the new material onto your Sphere in the scene view You should now notice your material in the inspector when you select the Sphere 24

25 A 3d object like the sphere we have is made using two components: MeshFilter MeshRenderer The Mesh Filter provides the point data The Mesh Renderer draws it to the screen We will need to grab the Mesh Renderer and the material from it to change the color of the object 25

26 The method GetComponent<Class> will grab a component from the Game Object if it exists If there is no Game Object it will return null, so make sure you check to see if it exists! We grab references to the Mesh Renderer and the Material in the Start method because we will continually be using them every Update By storing away references we don t have to perform costly searches for the components using GetComponent<>, which can slow things down if used too many times and too often Now that we have created a Game Object with some complexity, we might want to store it away for the future We can make our Game Object a Prefab, which is stored in our Project folder and reuse it over and over again To create a Prefab, grab the Sphere object and drag it into the Project Window Notice that the Sphere object s name in the Hierarchy is now blue 26

27 If we select the prefab in the project, it populates the inspector and any changes to it will spread to all other instances of the prefab in your scene If you select the prefab in the scene and make changes to it, you can push those changes to the global project prefab by pressing the Apply button at the top of the inspector You can also revert back to the project prefab if you made mistakes The Hierarchy panel also works as a Parent / Child Hierarchy display Create a new Cube Game Object and drag it onto the Sphere prefab Notice it is now nested within the Prefab Scale the Cube down and move it above the sphere so we can see it Try moving, rotating and scaling the prefab and you will see that it also impacts the child object 27

28 - Debug The Console window provides output from the program as it runs such as: Errors Warnings Logs We can output strings to the console using: Debug.Log( Hi, I am a string! ); - Debug Note that we can clear the console Collapse duplicate entries so they show only once Clear the next time we hit play Pause when errors occur Do not show log statements Do not show warnings Do not show errors Be careful with not showing errors, you might forget to turn it back on and wonder why nothing works 28

29 - Input Open up the Edit Menu at the upper right of the Unity Window Click on Project Settings and then Input The Inspector will now show the Input Manager with 18 predefined Inputs You can add more inputs by increasing the size of the array at the top - Input Many times the Action being performed is more important that what button is doing it We can name our Inputs and map them in multiple ways so that we can have several options available during gameplay The Type field allows us to switch from keyboard/mouse to mouse movement to joystick axes For now we only care about the names and what buttons we need to press, we ll cover this more deeply in the future 29

30 Input Methods 30