Week3 Examples:  Here is the source code to the examples.

1. Many Function Plots: (Last GTCSLib example)!
   • With proper abstraction, it is trivial to support large instances
   • XButton: cycles through all the plots
   • Try cycle through the plots and press-B button to see the PlotBox.
   • Bunch of random plots, interesting? May be yes? no? looks interestingly complex/chaotic, and yet we have absolute control!!
   • Class to check out: FunctionPlot:
     • Abstract the area upon which to plot the function as: PlotBox
     • Abstract x/y coverage of function to plot (mFunctionXCoverage and mFunctionYCoverage).
     • Notice: we can implement PlotFunction() even though we have no idea what is the function!!
     • GetYValue(x): is a virtual function, subclass can implement any function!
     • Check out the SineFunctionPath: implements a sine function.
   • Class to check out: ParabolaFunctionPath:
     • GetUseX(x):
       • must translate x by PlotBox.Width/2 (to see the negative side of the x values)
       • Scale the x values to cover the entire width of the PlotBox.
       • Notice that in UI, when you change the xCoverage, the plot does not change! (because we compensate the by the above scale).
       • This is done to show the curve stretching/squeezing with the PlotBox scale.
     • GetYValue(x):
       • Must call GetUseX(x) to offset and properly scale the x value
       • Scale the y-value such that, yCoverage value touches the upper corners of the plot area.
       • This means, when yCoverage is larger than plotBox.height, the traveling circle will go outside of bounds.
   • Class to check out: FunctionPath:
     • the update function now accepts a rotDelta (delta rotate) parameter.
     • causes the PlotBox to rotate.
   • Class to check out: PlotBox
     • Is a Rectangle: must set Center/Width/Height to be seen!
     • ComputePosition: uses the center position and width to compute LeftCenterPos.
     • Instance variable: NormalDir: this variable is always 90-degrees of FrontDirection
     • With FrontDirection and NormalDir, we have the x (FrontDirection) and y (NormalDir) directions.
     • In GetBoxPosition(x, y): we compute the actual position in the box by offsets to the x-direction vector (FrontDirectoin) and y-direction vector (NormalDir).
   
   
2. Unity in 2D with basic control: set to look in the positive z-direction. (default 2D window)
   • Main GUI: Game Editor Window, Inspector, Hierarchy, Project
   • Remember: to create defualt 2D game  (no worries if you don't remember, just set the MainCamera accordingly).
   • Unity project file: under Assets folder. Make sure you know where is your project!
   • 2D Environment: Main Camera setting (refer to the Inspector):
     • Position: (0, 0, -10)
     • Rotation: (0, 0. 0)
     • Projection: Orthographic
     • Size: 100 (this is half the world vertical size, from the middle of the screen to the top of game window)
     • Clipping Planes: Near (0.3 is good). Far: 1000
     • Now, our world:
       • +-100 in height (notice the total vertical size is actuall 200)
       • Left/Right is X (transform.right is the unit X-vector)
       • Up/Down is Y (transform.up is the unit Y-vector)
       • transform.forward: is the z axis direction.
   • To view the 3-D world: click on the 2D button at the top/left of the game editor window
   • To zoom into the game camera:, select "Main Camera" (from Hierarchy view):
     • GameObject-> Align View to Selected
   • The "Arrow" is an empty GameObject:
     • GameObject->CreateEmpty
     • Select the newly created object, in Inspector->Add Component -> Rendering -> Sprite Renderer
     • Drag image into the Project folder (import the image, will copy the image over to the project folder)
     • Drag the image from Project/Assets to SpriteRenderer->Sprite
     • Make Arrow size 10x10 (otherwise, you can't see it ... 1x1 can be difficult to see)
   • InteractiveControl.cs script:
     • this.transform.poition: location of the object
     • this.transform.up: Up/Down direction (use the up/down arrow)
     • this.transform.right: Right/Left direction (left/right arrows)
     • this.transform.RotateAround(Vector3.up, radians): rotates the object where Up/Right is rotated appropriatedly. After rotation, Up points in the rotated up direction.
     • Time.smoothDeltaTime (in second units). Hero's speed is 20 units per second and rotates at 45-degress per second.
     • Try this: for the HeroSpeed, change the private declaration to public and notice this becomes changeable from the UI (in the Inspector).
       • WARNING: any changes made in game mode will not be saved! (e.g., in this case if you change the HeroSpeed while in game mode, this change WILL NOT be saved!)
   • Debug: You can stop in the script, single step, examine variables, etc! 
     • Start game from Unity: in IDE Run->Attach Unity Debugger
     • in IDE: Green Button (Attach to Unity) [next time you run the game, debugger will be active]
        
3. Movements within Game Window Bounds:
   • GameManager: an empty GameObject (hanging off the MainCamera)
     • GlobalBehavior.cs script is hanging off here
     • mWorldBound, mMainCamera: see how these are initialized
     • UpdateWorldWindowBound() // <-- MUST be called when MainCamera is moved/zoomed
       • Derived current bound by orthographicsSize and aspect ratio.
     • ObjectCollideWorldBound(): returns the public enum status of WorldBoundStatus
   • EnemyBehavior.cs: Notice:
     • NewDirection():
       • We can change transform.forward to set a new heading for the game object.
       • But! this method does not work well at all (notice the spinning airplane!)
       • How to fix this? Next example
     • Update():
       • How we access the globalBehavior object by using Find() + GetComponent()
   • InteractiveControl.cs:
     • Map left/right arrow to rotation, more intuitive?
        
4. Improved Enemy Behavior: All changes are in EnemyBehavior.cs
   • Smaller world
   • Desire behavior after colliding with the world boundary: new direction is towards the world center rather than random (which may be continue away from the world, and can result in enemy spinning at the world edge).
   • Notice the new control on EnemyBehavior: mTowardsCenter:
     • Range is between 0 to 1
     • 0: Random half circle towards the world center
     • 1: Fly exactly towards the world center
   • Algorithm: refer to code comments. Here is the explaination.
     
     
5. Creation of Prefab (drag to Project/Asset from Hierarchy) + Many Enemies:
   • Prefab creation: "programming by example" drag an object (Enemy) from Hierarchy to Asset!
     • Created a subfolder to keep Asset folder proper.
     • NOTE: the "Resources" folder name is not an option!! Resources.Load(): depends on it!!
     • Deleted the Enemy object from the world
     • Changed EnemyBehavior::Start() (random spawning locations)
   • GlobalBehavior.cs::SpawnAnEnemy
     • How we keep track of time.
     • How to load from Resources folder.
     • How to Instantiate() from sample.
       
       
6. Support for collision:
   1. Both colliding bodies: must have collider defined and enabled.
   2. To response to a collision: two attributes
      • isTriggered: flag on Collider2D must be on.
      • RigidBody2D: must be defined.
   3. You can choose for both bodies to response to collision, or just one.
   4. In our case: Hero shhots Eggs, Egg and Enemy collide, Eggs participate, Enemy responses.
   • Hero (Arrow): InteractiveBehavior
     • Check for "Fire1" (left control)
     • Instantiate Egg as projectile (again, Egg must be in the Resources folder)
     • Notice: use GetComponent<ClassName> to get access to EggBehavior to set forward direction
     • Note: can also change GameObject's attributes (to change the egg's position)
   • Egg:
     • Must put a "collider" on all the collision parties (Component->Physics2D->Circular Collider 2D [easy to work with]).
       • NO need to check the "isTriggered" flag: only the collision handler [Enemy, in this case] needs it.
     • Prefab game object (don't forget to drag in EggBehavior!)
     • Behavior: allows outside to set its forward direction and simply moves forward
     • Speed: 100 units per second (multiplied with the Time.smoothDeltaTime)
     • How to shoot eggs at a slower rate?
     • How to destroy eggs outside of bound?
   • Enemy (the plane): colliding GameObject must have RigidBody, and IsTriggered (on Collider) switched on
     • First: RigidBody
       • Component->Physics 2D -> RigidBody 2D
       • Set Gravity Scale to 0 (switching off gravity)
     • Second: Collider
       • CircleCollider2D: IsTrigger: switched on
     • Third: implement OnTriggerEntered2D()
       • Notice the Destroy(gameObject) function to remove an object
       • Notice: Unity3D run time instantiated object names: "Egg(Clone)"
          
7. Changing Texture + GUI Text:
   • Moved textures into Resources/Textures folder (for runtime loading)
   • All actions in GlobalBehavior.Update() function (SpaceBar to see what the effects)
   • To change texture:
     • 1. Find the object
     • 2. Get the "SpriteRenderer"
     • 3. Set the sprite with what we want, in this case we load a texture that is already imported into Unit3D
   • To echo gui text::
     • 1. Create GUIText object (GameObject->UI->GUIText), give the text a proper name
     • 2. At run time, simply get the object, get the Component, and change!
   • Also changed: EnemyBehavior.OnTriggerEnger2D
     • Change enemy to eggs :-)
   • Audio:
     • Background: e.g., hang off GlobalBehavior (Add Component->Audio->AudioSource)
       • Loop + Play on Awake (on)
     • Hero eggin:
       • Check out the source
   • Build: File->Build Setting