I'll have a go at converting to DBC, but I'm not sure when it'll be ready. However the basic principles are in the code, so you could try and disect the code and have a go yourself.
EDIT
I've converted the code to work with DBC, I took quicker than I thought.
`****************************************************************************************
`**************************** HOW TILE BASED COLLISION WORKS ****************************
`**************************** by pizzaman ****************************
`**************************** Date: 14/6/04 ****************************
`**************************** Time to complete: 1 hour ****************************
`****************************************************************************************
`THE PRINCIPLE -
`The visible screen is devided up into boxes which we call tiles. This means that each
`tile is sitting on a range of coordinates. For example a 20 pixel by 20 pixel tile that
`is the top-left most tile is sitting on the coordinates (0,0) to (19,19). Since we know
`each tile is sitting on a range of coordinates we can check to see whether a sprite (or
`image) has the same coordinates as the tile. However, we must take into consideration
`that a sprite (or image) is usually bigger than a pixel, so we have to form a collision
`box around the sprite.
`HOW TO IMPLEMENT A TILE BASED COLLISION SYSTEM -
`Firstly we need a 2 dimensional array to store tile data in (Tile data is the image
`numbers of the of the images you are going to use; e.g. 1 could be a wall, 2 could be
`a grass image etc. Note: the image sizes should be the same as the tile size you will
`use.
`Secondly we store the data in the array. Note: you could already store data in an array
`and just load the array - this would be faster for loading times.
`Next we create some collision points around our sprite, usually 4 points which would
`be placed at the corners of the sprite creating a collision box, you could have more
`collision points if a collision box is not suitable.
`Next we have to figure out which tile in the array each collision point is on to do
`this you have to use the formula
`
` Tile = (x / Tile Sise, y / Tile size)
`
` where Tile is the tile in the array, x is the x coordinate of the
` collision point your checking for and y is the y coordinate of the
` collision point your checking for
`
`Now if the tile is a tile you dont want your sprite to go on; just reset the sprites
`coordinates to what they were before the collision and voila!!!! you've got tile
`based collision.
`****************************************************************************************
`*********************************** SCROLLING THE MAP **********************************
`****************************************************************************************
`THE PRINCIPLE -
`To scroll a tile based map, you simply have to move all the tiles in the given direction
`then when the tiles have moved more pixels then the size of the tiles, the tiles get
`reset to the positions they were in before they were moved, but their images changed
`to simulated the tiles have moved, and generating a seamless transition.
`HOW TO IMPLEMENT A SCROLLING TILE BASED MAP -
`Instead of using a system that relies on screen coordinates, we need to build our map
`on a global coordinate system where coordinates (0,0) is the first tile (usually the
`top-left most tile). Everything we do will be based in this global coordinate system,
`which will include the player and their collision system. The coordinates then will be
`transferred to screen coordinates, where the images can be pasted correctly.
`Note that an extra row and column of tiles are pasted to the screen, this is to
`generate the seamless scrolling.
`****************************************************************************************
`*********************************** Start of program ***********************************
`****************************************************************************************
`gosubs are here instead of actual code, just to make things look neat
gosub screensetup
gosub DeclareVariables
gosub createimages
gosub loaddata
gosub makeplayer
`start the main loop
do
`exit the loop if space bar is pressed - effectively ending the program
`Note: it has to be place here and not in a gosub as it wont work
if spacekey() = 1 then exit
gosub controls
gosub collision
gosub ScrollScreen
gosub displayplayer
gosub DisplayDebugInfo
`update screen
sync
loop
gosub cleanup
`end the program
end
`****************************************************************************************
`************************************* End of program ***********************************
`****************************************************************************************
screensetup:
`set screen resolution
set display mode 800,600,32
`setup syncing
sync on
sync rate 150
hide mouse
return
DeclareVariables:
`store how many horizontal/verticle tiles there are
NumOfTilesX = 40
NumOfTilesY = 40
`store the size (in pixels) of a tile
TileSizeX = 40
TileSizeY = 40
`store the speed of the tile
SpeedX = 2
SpeedY = 2
`store the coordinates that will make the player be at the centre of the screen
ScreenCentreX = 380
ScreenCentreY = 280
`store predefined coordinates of player
X1 = ScreenCentreX
Y1 = ScreenCentreY
`store predefined coordinates of map
MapX = 0
MapY = 0
return
createimages:
`create a green box
cls rgb(0,255,0)
get image 1,0,0,TileSizeX,TileSizeY
`create a yellow/orange box as the player
cls rgb(255,128,0)
get image 2,0,0,TileSizeX,TileSizeY
`create a red box
cls rgb(255,0,0)
get image 10,0,0,TileSizeX,TileSizeY
`create a blue box
cls rgb(0,0,255)
get image 11,0,0,TileSizeX,TileSizeY
return
loaddata:
`create an array called TileMap - we will use this to store the tile data.
`an array is like a file cabinet - in each drawer of the file cabinet there are
`folders that hold our data. Therefore in our "file cabinet" we have 20 drawers; and
`inside of each drawer we 15 folders; which hold data we want to access.
`Also arrays can have up to 5 dimensions (ours has 2 dimensions) - you can visualise
`this as being more folders inside of the other folders and so on; and of course you
`can just have 1 dimension array as well (in other words just the drawers)
dim TileMap(NumOfTilesX - 1,NumOfTilesY - 1)
`load data into the array - basically the computer will read 20 bits of data from one
`data statment (at the end of the program), then move onto the next data statment
`until all 15 data statments are read. Note: all 15 data statments could have been
`combined into one large data statment of 300 items; the reason why its not currently
`like that is its hard to read also you can kind of see the map the way its currently
`written.
for y = 0 to NumOfTilesY - 1
for x = 0 to NumOfTilesX - 1
read TileMap(x,y)
next x
next y
return
makeplayer:
`make the player
sprite 1,X1,Y1,2
`this sets the sprites properties; by placing a 0 in the backsave flag the background
`behind sprite will not be saved by the computer, hence will speed up our program a
`little. We are not using the backsave feature because we will be replacing the
`background ourselves; this is due to when a sprite is created the 3d backdrop is
`automatically created (a blue screen wiping any 2d images previously draw to the
`screen) and cannot be turned off as long as you have a sprite on screen.
set sprite 1,0,1
return
controls:
`store the map's x and y coordinates into the variables OldMapX and OldMapY
OldMapX = MapX
OldMapY = MapY
`store the x and y coordinates of the player into the variables oldX1 and oldY1
OldX1 = X1
OldY1 = Y1
`makes the player move by altering the sprites coordinates
`makes the map move by altering the maps coordinates, if the player is roughly at the
`centre of the screen
if leftkey() = 1
if MapX < X1 - (ScreenCentreX - 5) and MapX > X1 - (ScreenCentreX + 5) then MapX = MapX - SpeedX
X1 = X1 - SpeedX
endif
if rightkey() = 1
if MapX < X1 - (ScreenCentreX - 5) and MapX > X1 - (ScreenCentreX + 5) then MapX = MapX + SpeedX
X1 = X1 + SpeedX
endif
if upkey() = 1
if MapY < Y1 - (ScreenCentreY - 5) and MapY > Y1 - (ScreenCentreY + 5) then MapY = MapY - SpeedY
Y1 = Y1 - SpeedY
endif
if downkey() = 1
if MapY < Y1 - (ScreenCentreY - 5) and MapY > Y1 - (ScreenCentreY + 5) then MapY = MapY + SpeedY
Y1 = Y1 + SpeedY
endif
return
collision:
`NOTE : you may have noticed the player sticking to the blocks, to stop this make the
` collision area of the player smaller and edit the players image to the same
` same size (so it doesn't look weird). You have to make the change in the
` players x and y sizes greater or equal to their speed or you wont notice a
` difference.
`the following 8 lines of code stores the old and new left,right,top,bottom edges of
`the sprite in the respective variables
`gets which tiles the current left and right co-ordinates of the player are on
LeftTileNum = int(X1 / TileSizeX)
RightTileNum = int((X1 + (TileSizeX - 1)) / TileSizeX)
`gets which tiles the current top and bottom co-ordinates of the player are on
TopTileNum = int(Y1 / TileSizeY)
BottomTileNum = int((Y1 + (TileSizeY - 1)) / TileSizeY)
`gets which tiles the old left and right co-ordinates of the player are on
OldLeftTileNum = int(oldX1 / TileSizeX)
OldRightTileNum = int((oldX1 + (TileSizeX - 1)) / TileSizeX)
`gets which tiles the old top and bottom co-ordinates of the player are on
OldTopTileNum = int(oldY1 / TileSizeY)
OldBottomTileNum = int((oldY1 + (TileSizeY - 1)) / TileSizeY)
`this is where we check for those 4 collision points; if the collision point is on a
`tile you are not able to pass through (in our case a tile that has an image number
`of 10 or greater), then the old coordinates of the sprite are restored.
`Note: to have sliding collision we must check the the current x tile against the
`old y tile and vice versa.
`checks for top-left collision point
if TileMap(LeftTileNum, OldTopTileNum) >= 10 then X1 = oldX1 : MapX = OldMapX
if TileMap(OldLeftTileNum, TopTileNum) >= 10 then Y1 = oldY1 : MapY = OldMapY
`checks for top-right collision point
if TileMap(RightTileNum, OldTopTileNum) >= 10 then X1 = oldX1 : MapX = OldMapX
if TileMap(OldRightTileNum, TopTileNum) >= 10 then Y1 = oldY1 : MapY = OldMapY
`checks for bottom-left collision point
if TileMap(LeftTileNum, OldBottomTileNum) >= 10 then X1 = oldX1 : MapX = OldMapX
if TileMap(OldLeftTileNum, BottomTileNum) >= 10 then Y1 = oldY1 : MapY = OldMapY
`checks for bottom-right collision point
if TileMap(RightTileNum, OldBottomTileNum) >= 10 then X1 = oldX1 : MapX = OldMapX
if TileMap(OldRightTileNum, BottomTileNum) >= 10 then Y1 = oldY1 : MapY = OldMapY
`stops player from scrolling past the edges of the map by resetting the maps
`global coordinates to their maximum values. The maximum values are calculated by
`(TileSizeX * NumOfTilesInRow) - SpeedX - for MapX
`(TileSizeY * NumOfTilesInColumn) - SpeedY - for MapX
if MapX < 0 then MapX = 0
if MapX >= 798 then MapX = 798
if MapY < 0 then MapY = 0
if MapY >= 598 then MapY = 598
return
ScrollScreen:
`works out the tile number within array to start displaying tiles at
TileNumX = MapX / NumOfTilesX
TileNumY = MapY / NumOfTilesY
`cache calculation to tempX and TempY variables for a minor speed increase
`this calculation works out how many pixels to offset the position where the tile
`images should be placed.
TempX = MapX - (TileNumX * TileSizeX)
TempY = MapY - (TileNumY * TileSizeY)
`this pastes the images to screen in the correct order by working out where to start
`pasting the images from in the array, then displaying the images at the correct
`screen coordinates
for y = 0 to 15
for x = 0 to 20
paste image TileMap(x + TileNumX,y + TileNumY),(x * TileSizeX) - TempX,(y * TileSizeY) - TempY
next x
next y
return
displayplayer:
`display sprite
sprite 1,X1 - MapX,Y1 - MapY,2
return
DisplayDebugInfo:
text 0, 0,"FPS " + str$(screen fps())
text 0,20,"MapX " + str$(MapX)
text 0,40,"MapY " + str$(MapY)
text 0,60,"X1 " + str$(X1)
text 0,80,"Y1 " + str$(Y1)
text 100, 0,"Press spacebar to exit"
return
cleanup:
`delete any media involved in this program
for x = 1 to 11
if sprite exist(x) then delete sprite x
next x
delete image 1
delete image 2
delete image 10
delete image 11
return
`store tile data at the end of the program so its out of the way
data 10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10
data 10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10
data 10, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
data 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,10
data 10, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
data 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,10
data 10, 1, 1,11,11, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,11,11, 1, 1, 1
data 1, 1, 1,11,11, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,11,11, 1, 1,10
data 10, 1, 1,11,11, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,11,11, 1, 1, 1
data 1, 1, 1,11,11, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,11,11, 1, 1,10
data 10, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
data 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,10
data 10, 1, 1,11, 1,11, 1, 1, 1, 1, 1, 1, 1, 1,11, 1,11, 1, 1, 1
data 1, 1, 1,11, 1,11, 1, 1, 1, 1, 1, 1, 1, 1,11, 1,11, 1, 1,10
data 10, 1, 1,11, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,11, 1, 1, 1
data 1, 1, 1,11, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,11, 1, 1,10
data 10, 1, 1,11, 1,11, 1, 1, 1, 1, 1, 1, 1, 1,11, 1,11, 1, 1, 1
data 1, 1, 1,11, 1,11, 1, 1, 1, 1, 1, 1, 1, 1,11, 1,11, 1, 1,10
data 10, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
data 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,10
data 10, 1, 1,11,11, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,11,11, 1, 1, 1
data 1, 1, 1,11,11, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,11,11, 1, 1,10
data 10, 1, 1,11,11, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,11,11, 1, 1, 1
data 1, 1, 1,11,11, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,11,11, 1, 1,10
data 10, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
data 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,10
data 10, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
data 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,10
data 10, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
data 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,10
data 10, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
data 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,10
data 10, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
data 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,10
data 10, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
data 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,10
data 10, 1, 1,11,11, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,11,11, 1, 1, 1
data 1, 1, 1,11,11, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,11,11, 1, 1,10
data 10, 1, 1,11,11, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,11,11, 1, 1, 1
data 1, 1, 1,11,11, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,11,11, 1, 1,10
data 10, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
data 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,10
data 10, 1, 1,11, 1,11, 1, 1, 1, 1, 1, 1, 1, 1,11, 1,11, 1, 1, 1
data 1, 1, 1,11, 1,11, 1, 1, 1, 1, 1, 1, 1, 1,11, 1,11, 1, 1,10
data 10, 1, 1,11, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,11, 1, 1, 1
data 1, 1, 1,11, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,11, 1, 1,10
data 10, 1, 1,11, 1,11, 1, 1, 1, 1, 1, 1, 1, 1,11, 1,11, 1, 1, 1
data 1, 1, 1,11, 1,11, 1, 1, 1, 1, 1, 1, 1, 1,11, 1,11, 1, 1,10
data 10, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
data 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,10
data 10, 1, 1,11,11, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,11,11, 1, 1, 1
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data 10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10
data 10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10
