Well you wana write a scroller eh?

Well lets begin. Were going to write a pixel*pixel scroller using a camera.

The camera is the key in making the hole thing.

Cameras are used in 3d as well as 2d. Now let us begin.

First of all we need a camera type:



type tagCamera

CamX		as integer

CamY		as integer

endtype





this will be used to keep the player in sight. Will explain;)

but.. now lets set up our vars



use this to check for collision with tiles



Xtile=INT(PlayerX/TileSizeX)  'Tile Collision

Ytile=INT(PlayerY/TileSizeY)



Just add that to the map and you'll get tile colision:

if Map(Xtile,Ytile) = Whatever is solid then

Collision

endif



Now it's time to set up our camera



dim Camera as tagCamera



Camera.CamX=PlayerX-160

Camera.CamY=PlayerY-100



thats to keep the camera at the edge of the map.



Now lets check for edge of map collision



if Camera.CamX > (MaxMapX*TileSizeX)-320 then Camera.CamX=(MaxMapX*TileSizeX)-320

if Camera.CamY > (MaxMapY*TileSizeY)-200 then Camera.CamY=(MaxMapY*TileSizeY)-200

Thats for the lower right corner



if Camera.CamX <0 then Camera.CamX=0

if Camera.CamY <0 then Camera.CamY=0

Thats for the upper left corner



Now! lets do our engine

Note: Drawing command not in qb

This will be from a lib called Rellib



ok!



Xtile=INT(Camera.CamX/TileSizeX)   'To get start of tiles

Ytile=Int(Camera.CamY/TileSizeY)



TileX=Camera.CamX mod TileSizeX   'To get position in tile to draw

TileY=Camera.CamY mod TileSizeY



For Y= 0 to MaxY

	For X= 0 to MaxX

	Tile=map(X+Xtile,Y+Ytile)  'Add to map to get right tile

   RelSprite VARSEG(Buffer(0)),(X*TileSizeX)-TileX,(Y*TileSizeY)-TileY,VARSEG(Tile(1)),VARPTR(Tile(TileIndex(Tile)))

Next X,Y





Now that wasn't so hard

But remeber that the draw rountine is from a lib

Oops fogot to inform you of some vars



TileSizeX,TileSizeY=Size of your tile

MaxX,MaxY= Your TileSizeX/320 and TileSizeY/200

Note: Very important to Know this or you will get errors

MaxMapX= Amount of tile going across X * TileSizeX

MaxMapY= ""     "" ""   ""     ""     "" * TileSizY

e.i

 MaxMapX=26*16     

 MaxMapY=30*16



    a 26x30 map and 16x16 tiles



ok,before i forget

Use this to put down your hereo sprite



Xpos=Playerx-Camera.CamX

Ypos=Playery-Camera.CamY



Use this for NPC's



NPCX=NPCX-Camera.CamX

NPCY=NPCY-Camera.CamY



Note: Use a different var for the player

like e.i



Xpos is a var to center him

do not use Playerx=Playerx-Camera.CamX

or etc.

use only for NPC's

NPCX=NPCX-Camera.CamX

 



ok, Now you can make a killer scroller with kick ass nPC'S

heh...;)



E-mail me if any probs  kack@qbrpgs.com



-Kackurot 

cya!