1. Collisions with Static Objects
Lecture 6
Collisions with Static Objects
MazeDemo Tutorial

2. 1. Choose the size of the game space.
game space= 1200 x 900 pixels.
2. Choose a block size.
blocksize = 30 x 30 pixels
3. Compute size of game region in blocks.
game region = 40 x 30 blocks

3. 4. Create textures for blocks.
FINISH
4. Create textures for blocks.
5. Design game space.
wall
floor
START

4. 6. Define a code for block types
floor block = 1
wall block = 2

5. 7. Generate a 2D array of these values that
7. Generate a 2D array of these values that
matches the maze you have created

6. 8. Decide on format of maze array CSV file
40,30
2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2
2,1,1,1,1,1,1,1,1,1,2,2,2,1,1,1,1,2,1,1,2,1,1,1,1,1,1,1,1,2,2,1,1,2,2,2,1,1,1,2
2,1,2,1,1,1,2,1,1,1,1,1,1,1,1,1,1,2,1,1,2,1,1,1,1,1,1,1,1,1,2,2,1,2,1,1,1,1,1,2
2,1,1,1,2,1,1,1,2,1,2,1,2,1,1,1,1,2,1,1,2,1,2,2,2,1,2,2,2,1,1,1,1,2,1,2,1,1,1,2
2,1,2,1,1,1,2,1,1,1,2,1,2,1,1,1,1,2,1,1,2,1,1,1,2,1,2,1,2,2,2,1,2,2,1,2,1,1,1,2
2,1,1,1,2,1,1,1,2,1,2,1,2,1,1,1,1,2,1,1,2,2,2,1,2,1,2,1,2,2,2,1,1,2,1,2,2,2,2,2
2,1,2,1,1,1,2,1,1,1,2,1,2,1,1,1,1,2,1,1,2,1,1,1,2,1,2,1,2,1,1,1,2,2,1,1,1,1,1,2
2,1,1,1,2,1,1,1,2,1,2,1,2,1,1,1,1,2,1,1,1,1,2,2,2,1,2,1,2,1,2,2,2,2,2,1,2,1,1,2
2,1,2,1,1,1,2,1,1,1,2,1,2,1,1,1,1,2,2,2,2,2,2,2,2,1,2,1,2,1,2,1,2,1,2,2,2,1,1,2
2,1,1,1,2,1,1,1,2,1,2,1,2,2,2,2,1,2,1,1,1,1,1,1,1,1,2,1,2,1,2,1,2,1,1,1,2,1,1,2
2,1,1,1,1,1,1,1,1,1,2,1,1,1,2,1,1,2,1,1,1,1,2,2,2,1,2,1,1,1,1,1,2,1,2,1,2,1,1,2
2,2,2,2,2,2,2,2,2,2,2,1,1,1,2,2,2,2,1,1,1,1,2,1,2,1,2,1,2,2,2,2,2,1,2,1,2,1,1,2,
2,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,2,1,2,1,2,1,1,1,1,1,2,1,2,1,1,1,1,2
2,1,2,2,2,2,2,2,2,1,1,1,1,1,2,2,2,2,1,1,1,1,2,1,2,1,2,2,2,2,2,1,2,1,2,2,2,2,2,2
2,1,2,1,1,1,1,1,2,1,1,1,1,1,2,1,1,2,1,1,1,1,2,1,2,1,1,1,1,1,2,1,2,1,2,1,1,1,1,2
2,1,2,1,1,1,1,1,2,1,1,1,2,2,2,1,1,2,1,1,1,1,2,1,2,2,2,2,2,1,2,1,2,1,2,1,2,1,1,2
8. Decide on format of maze array
CSV file
header with num cols and num rows

7. The Cell Class Define a Cell class for the maze.
class Cell {
public int Block;
public Vector2 Pos;
public Cell(int block, int xpos, int ypos)
Block = block;
Pos.X = xpos;
Pos.Y = ypos; }
Define a Cell class for the maze.
type of texture block for the current Cell
position (upper left corner of cell in pixels

8. Class Level Variables 2D array of Cells defines the Maze
wall, floor, and player sprites
number of rows and columns of the Maze
width and height of the game space
size of each cell in units of pixels
KeyboardState object for monitoring keyboard events - used in update( )
speed of player in units of pixels
Cell[,] Maze;
Texture2D wall;
Texture2D floor;
Texture2D player;
Vector2 playerPos;
int nrow, ncol;
int gWidth = 1200;
int gHeight = 900;
int cellSize = 30;
KeyboardState kbrd;
int speed = 2;

9. Sizing the Game Space public Game1() {
graphics = new GraphicsDeviceManager(this);
graphics.PreferredBackBufferWidth = gWidth;
graphics.PreferredBackBufferHeight = gHeight;
Content.RootDirectory = "Content"; }

10. Initial Position of Player
protected override void Initialize() {
base.Initialize();
load_maze();
playerPos.X = cellSize + 1;
playerPos.Y = gHeight - 2*cellSize - 1; }

11. Loading the Maze Block Array
ncol
public void load_maze() {
string str;
StreamReader tr = new StreamReader("maze_data.csv");
str = tr.ReadLine();
string[] stary = str.Split(',');
ncol = Convert.ToInt32(stary[0]);
nrow = Convert.ToInt32(stary[1]);
Maze = new Cell[nrow, ncol];
for (int r = 0; r < nrow; r++)
stary = str.Split(',');
for (int c = 0; c < ncol; c++)
Maze[r, c] = new Cell(Convert.ToInt32(stary[c]),c*cellSize,r*cellSize); }
tr.Close();
. . .
nrow
. . .
. . .
maze_data.csv

12. Managing the Content Pipeline
protected override void LoadContent() {
spriteBatch = new SpriteBatch(GraphicsDevice);
wall = Content.Load<Texture2D>("awall");
floor = Content.Load<Texture2D>("afloor");
player = Content.Load<Texture2D>("aplayer"); }

13. controlling player motion
The Update( ) Method
controlling player motion
protected override void Update(GameTime gameTime) {
if (GamePad.GetState(PlayerIndex.One).Buttons.Back ==
ButtonState.Pressed || Keyboard.GetState().IsKeyDown(Keys.Escape))
Exit();
kbrd = Keyboard.GetState();
if (kbrd.IsKeyDown(Keys.Up) && moveOK(0, playerPos))
playerPos.Y -= speed;
if (kbrd.IsKeyDown(Keys.Down) && moveOK(2, playerPos))
playerPos.Y += speed;
if (kbrd.IsKeyDown(Keys.Left) && moveOK(3, playerPos))
playerPos.X -= speed;
if (kbrd.IsKeyDown(Keys.Right) && moveOK(1, playerPos))
playerPos.X += speed;
base.Update(gameTime); }
playerPos 1 2 3
direction of player motion

14. moveOK( ) r2,c2 r1,c1 r2,c2 r1,c1 r2,c2 r1,c1 r2,c2 r1,c1
public bool moveOK(int dir, Vector2 pos) {
int r1, c1, r2, c2;
bool rtnval = true;
if (dir == 0)
r1 = (int)(playerPos.Y+1-speed) / cellSize;
c1 = (int)(playerPos.X+1) / cellSize;
r2 = r1;
c2 = (int)(playerPos.X + cellSize-2) / cellSize;
if (Maze[r1, c1].Block == 2 || Maze[r2, c2].Block == 2)
rtnval = false; }
if (dir == 2)
r1 = (int)(playerPos.Y-1 + cellSize-2 + speed) / cellSize;
if (dir == 1) {
r1 = (int)(playerPos.Y + 1) / cellSize ;
c1 = (int)(playerPos.X + cellSize speed) / cellSize;
r2 = (int)(playerPos.Y + cellSize - 2) / cellSize;
c2 = c1;
if (Maze[r1, c1].Block == 2 || Maze[r2, c2].Block == 2)
rtnval = false; }
if (dir == 3)
r1 = (int)(playerPos.Y + 1) / cellSize;
c1 = (int)(playerPos.X - speed) / cellSize;
return rtnval;

15. the Draw( ) Method
protected override void Draw(GameTime gameTime) {
GraphicsDevice.Clear(Color.CornflowerBlue);
spriteBatch.Begin();
for (int r = 0; r < nrow; r++)
for (int c = 0; c < ncol; c++)
if (Maze[r, c].Block == 1)
spriteBatch.Draw(floor, Maze[r, c].Pos, Color.White);
else
spriteBatch.Draw(wall, Maze[r, c].Pos, Color.White); }
spriteBatch.Draw(player, playerPos, Color.White);
spriteBatch.End();
base.Draw(gameTime);
this section draws 1200 blocks for every frame of animation
if the maze layout is constant we could simply load it as a background image
this command draws the player