Week 1 Examples: MVC + Speed + Direction + Velocity + Path SoruceCode zip flie

1. EmptyTemplate Project:
• Completely empty project.
• Good to begin programming with GTCS1Lib.
• API model: Init, Update, and Draw
• Assumption on underlying: there is a "model"
• What is the model? Well, you game!
• Assets: REQUIREMENT folder structure
• Resources with three subfolders: Audio/Fonts/Textures
• Spelling must be correct, organization is required
• Build property for the asset files!! ß Make sure you know what this is, otherwise, you will waste a lot of time!! (If you add in a texture but it does not show in your game, THIS IS THE CAUSE!)
• Things to note:
• Do not create graphical primitives before InitializeWorld() is called (system initialization may not be completed)
• Opaque texture on circle shows rectangle image
• SetWindowPixelDimension(): can only be called from InitalizeWorld() [bad limitation: cannot toggle full screen during runtime!]
• Development environment:
• Solution vs Project names
• Icon image
• Compile target name
• Default file and class names
• Default namespace names
• Default executable file location and name
• Default game window title bar name
• GUID name of the app.
• Useless stuff in the development environment that you should remove before sharing your source code
  
  
2. MVC: Model-View-Controller
• Model: user defined, should be in a separate class representing your game state. Must persist over Update/Draw cycles. In our case, instance variable of your class subclassing from XNACS1Base class.
• View: The DrawWorld() function. By default, drawing happens automatically. No need to do anything, except when you want to avoid drawing an object (RemoveFromAutoDrawSet()).
• Controller: The UpdateWorld() function, accepts user input and modify the Model accordingly.
• In this Examples
• Model: SoccerTarget, you can create one, update it (moves towards the right), and destroy it.
• Controller: A: to create, B: to destroy, Right-ThumbStick: to move it.
• Try: press-A button multiple times. See left over soccer, why? How to handle this? (RemoveFromAutoDrawSet());
  
  
3. Speed:
• A-Button to shoot the ball,
• Right-Thumb-Stick-Up/Down to change the speed
• Only function to pay attention to is: ComputeBallSpeed()
• This example (in fact most examples) are not designed according to MVC, this is for illustrating specific concept!
• Note the World.TicksInASecond constant, this is a not-very accurate approximation of number of UpdateWorld() functions call in a second.
• Note, it is accurate that we cover 100 units in exactly 200 updates.
• Our game world is defined against "Update" calls and not against wall clock.
• Notice:
• ShouldTravel
• Velocity (different from Speed)
• AutoDrawSet functions: AddTo and RemoveFrom (default: all created primitives are in AutoDrawSet)
  
  
4. Constant speed with changing direction:
• A-Button to assign a new direction for the ball.
• Only function to pay attention to is: SetRandomBallVelocityDir()
• Allocate a random direction (call RandomFloat())
• Normalize the direction
• Ball's velocity is the normalized random vector multiplied by the speed
• IMPORTANT: notice the UseXNACS1Lib compiler directive: the library supports setting velocity direction (mBall.VelocityDirectoin) and speed separately (mBall.Speed)
  
  
5. Constant direction with varying speed:
• A-Button to assign a new direction for the ball.
• Right-Thumb-Stick-Up/Down to change the speed
• Interesting point:
• UseXNACS1Lib: DOES NOT WORK!! As the speed decreases and approaches zero, the ball starts move randomly!! (lost direction information when speed is zero).
  
  
6. Vectors and Seeing Vectors:
• A-Button: to add a new Vector at the end of the current one
• B-Button: Clear all existing work
• Left-Thumb-Y: increase/decrease vector size
• Right-Thumb: change current vector direction
• ShowVector class:
• math: Pay attention to the UpdateEndPoints() function.
• XGCS1Lib: RemoveFromAutoDrawSet(),
• Update Vector by right thumbStick notice: Normalize() what happens if we don't call this function?
• Button-B: World.RemoveAllFromDrawSet()!
  
  
7. Changing velocity and speed:
• B-Button: to change direction of the ball (with same speed)
• A-Button: will change the speed without changing the direction
• Now, lets look at the colorful line again: constant speed (towards the right)
• But, what if instead of moving towards the right, I want to move in some other directions?
• Roads are now instance variables (to avoid re-creating rectangles)
• GenerateRandomBallVelocityDirection(): notice:
• RandomFloat function
• Normalize()
• SetEndPoints()
• How we line up the roads: line equation somewhere?
• The two options in the for loop for computing nextPos
• Notice: TopOfAutoDrawSet() (in button B Clicked)
  
  
8. Ball follow path: Define and implement a soccer ball that continuously follow the vector-segments defined (follow the direction). The soccer ball should cover each segment in a fixed amount of time (faster on the short segments and slower on the longer segments). This goal of this exercise/example is to demonstrate direction (velocity) and magnitude (speed) of vectors.
• Left Thumb-Stick-Y: Change current road segment length
• Left Thumb-Stick-X: Change how much time the soccer ball has to cover the segment
• Right Thumb-Stick: Change current road segment direction
• A-Button: Add in new road segment
• Ball follows current segment of road it is on
• MySoccer class: it has AI!? no!!
• A Simple Finite State Machine, treats each "Road Segment" as a distinct state
• mCurrentRoadSegment as indication of which "state" it is in
• State transitions:
• if travelled distance > current segment size, transit to next state (next road segment)
• if at the very last state (last segment), transit to the first state again.
• Road class: simple array of ShowVector
• Update(): of main program is simple:
• Handle User: Insert new road segment
• Handle User: Get new direction/size for current road segment
• Handle internal behavior (AI): Tell ball to update itself (because road's new values)
• Handle boundary condition (win/loose): Reset if necessary
• If last segment direction change while the ball is on it, have to make sure the ball follows!! Can we make the ball “stick” to the road?
  
  
9. Ball sticking to path using distance travelled: Identical to the above example, only differences are
• Instead of moving ball from what every position it is in towards the end of the current road-pathway, we make sure the ball is actually on the road.
• All the actions are in MySoccer::UpdateBallDirAndSpeed():
• travelled: distance already travelled along the road.
• Center = road.StartPos + travelled * dirOfRoad
• Notice, we try to adjust the Speed according to the remaining distance left.
  
  
10. Ball stick to path using number of ticks left: exactly the same as above, the only differences here are:
• mNumTicksLeft: this is the instance variable inside the MySoccer class telling us how many more ticks before we come to the end of the current road segment.
• Update(): notice the state transition condition is trivial now! Just check if we have use up all the ticks.
• Once again, all the actions are in the MySoccer::UpdateBallDirAndSpeed() function:
• Change mNumTicksLeft if this is negative (meaning we are beginning a new road segment)
• Center position is now a percentage of ticks that has happened, percentage of the entire road length
• User shortening path may cause ball to travel backwards!
• We still compute speed according to how much distance left we have to travel.
• General Observation:
• Process Button-A first or process Button-B first? (try it!)
• Does not really matter (unless you press both buttons at the same time J).