1. 2D Platform Games: Tiles & Scrolling

2. Platform Games Character jumps from platform to platform
World terrain is made of tiles
Add player, bad guys, power ups

3. Creating the game map Make the world (game map) for one level.
Don’t use one huge image!
Use grid – each slot points to a tile image or null

4. Issues with Drawing the World
Tile world is bigger than screen
Need to move the screen (instead of the player, often)
Often want background image that moves slower than the rest of the world

5. Calculate New Position
Keep the player in the middle of the screen…
Percentage of left and right of screen that makes the scroll happen
if (Player.Position.X < marginLeft)
cameraMovement = Player.Position.X - marginLeft

6. Offset Don’t scroll off ends:
float maxCameraPosition = Tile.Width * Width – viewport.Width;
That is, (the width of one tile * # tiles in a row) – (width of screen)
Screen

7. Drawing the Tiles Efficiency: only draw visible tiles:
int left = (int)Math.Floor(cameraPosition/Tile.Width);
int right = left + <viewport width>/Tile.Width;
right = Math.Min(right, Width-1) // where Width is the width of the 2D table.

8. Drawing the Sprites Not many – just draw all (brute force)
Many – only draw visible sprites
Keep sprites in a list ordered by position
Partition map into screen – sized portions, keep sprites from each portion

9. Drawing Backgrounds Choices:
Keep background static
Scroll background image at same rate as tiles
Scroll background image slower to mimic distance
Last method is known as Parallax Scrolling

10. Scrolling Often will have segments of backgrounds.
As scrolling happens, rotate backgrounds.
Usually no more than 2 backgrounds segments drawn at any given time.