1. Sprite Sheets, Game States
Arjan Egges & Paul Bergervoet

2. Overzicht

3. Sprite sheets Strips vs. Sheets Strip is handiger met tekenen 
Soms is een strip te breed om in het videogeheugen te passen 
Sheet kan meer sprites bevatten dan strip 
Sheet is wat onhandiger om te tekenen 

4. Sprite strip tekenen in Jewel Jam
public override void Draw(GameTime gameTime, SpriteBatch s) {
if (!visible)
return;
Rectangle source = new Rectangle(variation * sprite.Height, 0,
sprite.Height, sprite.Height);
s.Draw(sprite, GlobalPosition, source, Color.White);
glitters.Draw(gameTime, spriteBatch); }

5. Nieuwe klasse SpriteSheet
SpriteSheet heeft een aantal rijen en kolommen
Er is een ‘sheet index’ die aangeeft welk element van de sheet we willen tekenen.
4 kolommen 1 2 3 4 5 6 7
2 rijen

6. SpriteSheet class SpriteSheet { protected Texture2D sprite;
protected int sheetIndex;
protected int sheetColumns;
protected int sheetRows;
protected bool mirror;
public SpriteSheet(string assetname, int sheetIndex = 0)
... }

7. Sprite sheet instellingen
Bij het laden van een asset zijn er dan drie mogelijkheden:
Het is een enkele sprite
Het is een sprite strip
Het is een sprite sheet
Trucje: encodering in de filenaam!
spr_help.jpg

8. String ‘ontleden’ in de constructor
sprite = PenguinPairs.AssetManager.getSprite(assetname);
this.sheetIndex = sheetIndex;
this.sheetColumns = 1;
this.sheetRows = 1;
string[] assetSplit =
if (assetSplit.Length <= 1)
return;
string sheetNrData = assetSplit[assetSplit.Length - 1];
string[] colrow = sheetNrData.Split('x');
this.sheetColumns = int.Parse(colrow[0]);
if (colrow.Length == 2)
this.sheetRows = int.Parse(colrow[1]);
Levert een array op van strings.
Blijkbaar is het geen
strip of sheet.
sheet (rijen en kolommen)

9. Properties public int Width { get return sprite.Width / sheetColumns;}
public int Height
return sprite.Height / sheetRows;
Deel door het aantal kolommen
voor de juiste breedte.
Deel door het aantal rijen
voor de juiste hoogte.

10. Meer properties public int NumberSheetElements {
get { return this.sheetColumns * this.sheetRows; } }
public int SheetIndex
get { return this.sheetIndex; }
set
if (value < NumberSheetElements && value >= 0)
this.sheetIndex = value;
= totaal aantal elementen
Alleen toekennen als het mag.

11. SpriteSheet tekenen
public override void Draw(SpriteBatch spriteBatch, Vector2 position,
Vector2 origin) {
int columnIndex = sheetIndex % sheetColumns;
int rowIndex = sheetIndex / sheetColumns;
Rectangle spritePart = new Rectangle(columnIndex * this.Width,
rowIndex * this.Height,
this.Width, this.Height);
SpriteEffects spriteEffects = SpriteEffects.None;
if (mirror)
spriteEffects = SpriteEffects.FlipHorizontally;
spriteBatch.Draw(sprite, position, spritePart, Color.White,
0.0f, origin, 1.0f, spriteEffects, 0.0f); }
Bereken de juiste
rij/kolom waarden.

12. SpriteGameObject klasse
protected SpriteSheet sprite;
protected Vector2 origin;
public SpriteGameObject(string assetname, int layer = 0,
string id = "", int sheetIndex = 0) : base(layer, id) {
if (assetname != "")
sprite = new SpriteSheet(assetname, sheetIndex);
else
sprite = null; }
public override void Draw(GameTime gameTime, SpriteBatch s) {
if (!visible || sprite == null)
return;
sprite.Draw(spriteBatch, this.GlobalPosition, origin);

13. SpriteGameObject gebruiken
protected override void LoadContent() {
...
gameWorld = new GameObjectList();
gameWorld.Add(
new SpriteGameObject("spr_background_levelselect"));
SpriteGameObject penguin =
new 1, "penguin");
penguin.Position = new Vector2(500, 420);
gameWorld.Add(penguin); }

14. SpriteGameObject gebruiken
protected void HandleInput() {
inputHelper.Update();
if (inputHelper.KeyPressed(Keys.Escape))
this.Exit();
if (inputHelper.KeyPressed(Keys.F5))
SetFullScreen(!graphics.IsFullScreen);
gameWorld.HandleInput(inputHelper);
SpriteGameObject penguin;
penguin = gameWorld.Find("penguin") as SpriteGameObject;
if (inputHelper.KeyPressed(Keys.Left))
penguin.SheetIndex--;
else if (inputHelper.KeyPressed(Keys.Right))
penguin.SheetIndex++; }

15. Menu’s
Tekst
Aan/uit knop
Slider

16. TextGameObject class TextGameObject : GameObject {
protected SpriteFont spriteFont;
protected Color color;
protected string text;
public TextGameObject(string assetname, int layer = 0, string id = "")
: base(layer, id)
spriteFont = PenguinPairs.AssetManager.Content.Load<SpriteFont>(assetname);
color = Color.White; }
...

17. TextGameObject
public override void Draw(GameTime gameTime, SpriteBatch s) {
if (visible)
spriteBatch.DrawString(spriteFont, text, this.GlobalPosition, color); }
public Color Color
get { return color; }
set { color = value; }
public string Text
get { return text; }
set { text = value; }

18. Knoppen: muisklik detecteren
Hoe weten we of op een knop geklikt wordt?
Muisknop ingedrukt
Muis is binnen de rechthoek die de knop omsluit
BoundingBox property toevoegen aan SpriteGameObject:
public override Rectangle BoundingBox {
get
int left = (int)(GlobalPosition.X - origin.X);
int top = (int)(GlobalPosition.Y - origin.Y);
return new Rectangle(left, top, Width, Height); }

19. Eenvoudige knop class Button : SpriteGameObject {
protected bool pressed;
public Button(string imageAsset, int layer = 0, string id = "")
: base(imageAsset, layer, id)
{ }
public override void HandleInput(InputHelper inputHelper) {
pressed = inputHelper.MouseLeftButtonPressed() &&
BoundingBox.Contains((int)inputHelper.MousePosition.X,
(int)inputHelper.MousePosition.Y); }
public bool Pressed
{ get { return pressed; } }

20. Aan/uit knop (toggle) class OnOffButton : SpriteGameObject {
public OnOffButton(string imageAsset, int layer = 0, string id = "")
: base(imageAsset, layer, id, 0) }
public override void HandleInput(InputHelper inputHelper)
if (inputHelper.MouseLeftButtonPressed() &&
BoundingBox.Contains((int)inputHelper.MousePosition.X,
(int)inputHelper.MousePosition.Y))
sheetIndex = (sheetIndex + 1) % 2;
...

21. Aan/uit knop (toggle) public bool On { get
return sprite.SheetIndex == 1; }
set
if (value)
sprite.SheetIndex = 1;
else
sprite.SheetIndex = 0;

22. Slider class Slider : GameObjectList {
protected SpriteGameObject back, front;
protected bool dragging;
protected int leftmargin, rightmargin;
public Slider(string sliderback, string sliderfront, int layer = 0,
string id = "") : base(layer, id) }
...

23. Slider
public Slider(string sliderback, string sliderfront, int layer = 0,
string id = "") : base(layer, id) {
leftmargin = 5;
rightmargin = 7;
back = new SpriteGameObject(sliderback, 0);
this.Add(back);
front = new SpriteGameObject(sliderfront, 1);
front.Position = new Vector2(leftmargin, 8);
this.Add(front);
dragging = false; }

24. Slider public override void HandleInput(InputHelper inputHelper) {
if (inputHelper.MouseLeftButtonDown()) {
if (back.BoundingBox.Contains((int)inputHelper.MousePosition.X,
(int)inputHelper.MousePosition.Y) || dragging)
float newxpos = MathHelper.Clamp(inputHelper.MousePosition.X -
back.GlobalPosition.X - front.Width / 2, back.Position.X + leftmargin,
back.Position.X + back.Width - front.Width - rightmargin);
front.Position = new Vector2(newxpos, front.Position.Y);
dragging = true; }
else
dragging = false;

25. Slider public float Value { get
return (front.Position.X - back.Position.X - leftmargin) /
(back.Width - leftmargin - rightmargin - front.Width); }
set
float newxpos = value * (back.Width - leftmargin - rightmargin –
front.Width) + back.Position.X + leftmargin;
front.Position = new Vector2(newxpos, front.Position.Y);

26. Game states Veel games hebben verschillende game toestanden Hoofdmenu
Optiemenu
Helpmenu
Aan het spelen
Game over
Highscore …

27. goede klassenstructuur!
Game states
Noemen we ook wel: Game states
Hoe representeren we die toestanden?
Hoe wisselen we tussen toestanden?
Maak gebruik van een
goede klassenstructuur!

28. Ad hoc manier in Jewel Jam
public override void HandleInput(InputHelper inputHelper) {
if (title.Visible) {
if (inputHelper.KeyPressed(Keys.Space))
title.Visible = false; }
else if (this.GameOver)
this.Reset();
else
...
Per game state andere
invoer afhandelen.

29. Ad hoc manier in Jewel Jam
Zelfde idee in Update.
public override void Update(GameTime gameTime) {
if (this.GameOver && !gameover.Visible)
gameover.Visible = true;
JewelJam.AssetManager.playSound("snd_gameover"); }
else if (!helpFrame.Visible && !title.Visible)
base.Update(gameTime);
Kan tot verwarring leiden!

30. Algemeen game loop object
Definieer een interface met daarin alle belangrijke game loop methoden.
interface IGameLoopObject {
void HandleInput(InputHelper inputHelper);
void Update(GameTime gameTime);
void Draw(GameTime gameTime, SpriteBatch spriteBatch);
void Reset(); }

31. Klassen implementeren de interface
Ook de GameObject klasse!
class GameObject : IGameLoopObject {
protected GameObject parent;
protected Vector2 position, velocity;
protected int layer;
protected string id;
protected bool visible;
... }

32. Game state manager class GameStateManager : IGameLoopObject {
protected Dictionary<string, IGameLoopObject> gameStates;
protected IGameLoopObject currentGameState;
public GameStateManager()
gameStates = new Dictionary<string, IGameLoopObject>();
currentGameState = null; }
...

33. Game state manager
public void AddGameState(string name, IGameLoopObject state) {
gameStates[name] = state; }
public IGameLoopObject GetGameState(string name)
return gameStates[name];
public IGameLoopObject CurrentGameState
get
return currentGameState;

34. public void SwitchTo(string name){
if (gameStates.ContainsKey(name))
currentGameState = gameStates[name]; }

35. Game state manager public void HandleInput(InputHelper inputHelper) {
if (currentGameState != null)
currentGameState.HandleInput(inputHelper); }
public void Update(GameTime gameTime) {
currentGameState.Update(gameTime);
public void Draw(GameTime gameTime, SpriteBatch spriteBatch) {
currentGameState.Draw(gameTime, spriteBatch);
...

36. In PenguinPairs Static membervariabele: Met property:
protected static GameStateManager gameStateManager;
public static GameStateManager GameStateManager {
get { return gameStateManager; } }

37. class TitleMenuState : GameObjectList {
protected Button playButton, optionButton, helpButton;
public TitleMenuState() {
// create the game objects... }
public override void HandleInput(InputHelper inputHelper) {
base.HandleInput(inputHelper);
if (playButton.Pressed)
PenguinPairs.GameStateManager.SwitchTo("levelMenu");
else if (optionButton.Pressed)
PenguinPairs.GameStateManager.SwitchTo("optionsMenu");
else if (helpButton.Pressed)
PenguinPairs.GameStateManager.SwitchTo("helpState");

38. class OptionsMenuState : GameObjectList {
protected Button backButton;
protected Slider musicVolumeSlider;
protected OnOffButton onOffButton;
public override void HandleInput(InputHelper inputHelper) {
base.HandleInput(inputHelper);
if (backButton.Pressed)
PenguinPairs.GameStateManager.SwitchTo("titleMenu"); }
public override void Update(GameTime gameTime) {
base.Update(gameTime);
MediaPlayer.Volume = musicVolumeSlider.Value;
...

39. In PenguinPairs protected override void LoadContent() {
spriteBatch = new SpriteBatch(GraphicsDevice);
screen = new Point(1200, 900);
this.SetFullScreen(false);
gameStateManager.AddGameState("titleMenu",
new TitleMenuState());
gameStateManager.AddGameState("optionsMenu",
new OptionsMenuState());
gameStateManager.AddGameState("levelMenu",
new LevelMenuState());
gameStateManager.AddGameState("helpState",
new HelpState());
gameStateManager.SwitchTo("titleMenu"); }

40. In PenguinPairs protected void HandleInput() { inputHelper.Update();
if (inputHelper.KeyPressed(Keys.Escape))
this.Exit();
if (inputHelper.KeyPressed(Keys.F5))
SetFullScreen(!graphics.IsFullScreen);
gameStateManager.HandleInput(inputHelper); }

41. In PenguinPairs protected override void Update(GameTime gameTime) {
HandleInput();
gameStateManager.Update(gameTime); }
protected override void Draw(GameTime gameTime)
GraphicsDevice.Clear(Color.Black);
spriteBatch.Begin(SpriteSortMode.Deferred, null, null, null, null,
null, spriteScale);
gameStateManager.Draw(gameTime, spriteBatch);
spriteBatch.End();