2d Collison advice - GameCreators Forum

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ConorH

22

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Joined: 5th Feb 2003

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Posted: 3rd Jan 2005 02:34

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Im trying to get my game to load a map and have the little sprite character walk about and not walk into certain things. Does anyone have any good resouces for tutorials or methods to create a system like mine. I noticed that DBPro has a dodgy Pixel perfect collison detection, but this doesnt bother me much as the map is based on 32*32 tiles.

Would it be wise to make each tile a sprite, or just to paste the whole map to the screen. I Also tried to use Sprite collision(1,0) but it returned it even when my only sprite on the screen is the main character (1). Any advice on that and anything else is appreciated

Thanks

its my new rat tail dog!

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pizzaman

21

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Joined: 18th Feb 2004

Location: Gateshead, UK

Posted: 3rd Jan 2005 05:04

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hi

Heres something I made a while ago - its kind of a mini tutorial. Its split into 2 programs, the first deals with collision of a tile map, the second part scrolls it with collision implemented. If you just run the code the second part is automatically run.

`****************************************************************************************
`**************************** 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.

`rem out along with the ending one to execute this program
remstart

`gosubs are here instead of actual code, just to make things look neat
gosub screensetup
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

`call our home made function for displaying the tiles
   PasteTiles()

gosub displayplayer

`update screen
   sync

loop

gosub cleanup

`end the program
end

`****************************************************************************************
`************************************* End of program ***********************************
`****************************************************************************************

screensetup:

`delete anything stored in video memory
   flush video memory

`set screen resolution
   set display mode 800,600,32

`setup syncing
   sync on
   sync rate 150

return

createimages:

`create a green box
   cls rgb(0,255,0)
   get image 1,0,0,40,40,1

`create a yellow box as the player
   cls rgb(255,255,0)
   get image 2,0,0,40,40,1

`create a red box
   cls rgb(255,0,0)
   get image 10,0,0,40,40,1

`create a blue box
   cls rgb(0,0,255)
   get image 11,0,0,40,40,1

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(20,15)

`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 14

for x = 0 to 19

read TileMap(x,y)

next x

next y

return

makeplayer:

`store predefined coordinates of player
   x1 = 380
   y1 = 280

`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 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
   if leftkey()  = 1 then x1 = x1 - 2
   if rightkey() = 1 then x1 = x1 + 2
   if upkey()    = 1 then y1 = y1 - 2
   if downkey()  = 1 then y1 = y1 + 2

return

collision:

`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 / 40)
   RightTileNum  = int((x1 + 39) / 40)
   `gets which tiles the current top and bottom co-ordinates of the player are on
   TopTileNum    = int(y1 / 40)
   BottomTileNum = int((y1 + 39) / 40)

`gets which tiles the old left and right co-ordinates of the player are on
   OldLeftTileNum   = int(oldx1 / 40)
   OldRightTileNum  = int((oldx1 + 39) / 40)
   `gets which tiles the old top and bottom co-ordinates of the player are on
   OldTopTileNum    = int(oldy1 / 40)
   OldBottomTileNum = int((oldy1 + 39) / 40)

`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
   if TileMap(OldLeftTileNum, TopTileNum)        >= 10 then y1 = oldy1

`checks for top-right collision point
   if TileMap(RightTileNum,    OldTopTileNum)    >= 10 then x1 = oldx1
   if TileMap(OldRightTileNum, TopTileNum)       >= 10 then y1 = oldy1

`checks for bottom-left collision point
   if TileMap(LeftTileNum,    OldBottomTileNum)  >= 10 then x1 = oldx1
   if TileMap(OldLeftTileNum, BottomTileNum)     >= 10 then y1 = oldy1

`checks foe bottom-right collision point
   if TileMap(RightTileNum,    OldBottomTileNum) >= 10 then x1 = oldx1
   if TileMap(OldRightTileNum, BottomTileNum)    >= 10 then y1 = oldy1

return

displayplayer:

`display sprite
   sprite 1,x1,y1,2

`show frame rate (also sometimes its useful to display debug info like player
   `player positions, program specific variables etc)
   text 10,10,str$(screen fps())

return

cleanup:

`delete any media involved in this program
   for x = 1 to 11
      if image exist(x) then delete image x
      if sprite exist(x) then delete sprite x
   next x

`delete anything thats left in the video memory - if anything
   flush video memory

return

`this is a simple user defined function - all it does is paste the tile images to the
`screen in the correct order from the array
function PasteTiles()

for y = 0 to 14

for x = 0 to 19

paste image TileMap(x,y),x*40,y*40

next x

next y

endfunction

`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, 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, 1,10
data 10, 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, 1,10
data 10, 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, 1,10
data 10, 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, 1,10
data 10, 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, 1,10
data 10, 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, 1,10
data 10, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,10
data 10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10

`rem out this along with the starting one to execute this program
remend

`****************************************************************************************
`**************************** HOW TO SCROLL A TILE BASED MAP ****************************
`****************************          by pizzaman           ****************************
`**************************** Date:             11/7/04      ****************************
`**************************** Time to complete: 30 mins      ****************************
`****************************************************************************************

`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:

`delete anything stored in video memory
   flush video memory

`set screen resolution
   set display mode 800,600,32

`setup syncing
   sync on
   sync rate 150

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
   box 0,0,TileSizeX,TileSizeY,rgb(0,255,0),rgb(0,225,0),rgb(0,225,0),rgb(0,200,0)
   get image 1,0,0,TileSizeX,TileSizeY,1

`create a yellow/orange box as the player
   box 0,0,TileSizeX,TileSizeY,rgb(255,255,0),rgb(255,128,0),rgb(255,128,0),rgb(255,255,0)
   get image 2,0,0,TileSizeX,TileSizeY,1

`create a red box
   cls rgb(255,0,0)
   get image 10,0,0,TileSizeX,TileSizeY,1

`create a blue box
   box 0,0,TileSizeX,TileSizeY,rgb(0,0,255),rgb(0,0,225),rgb(0,0,225),rgb(0,0,200)
   get image 11,0,0,TileSizeX,TileSizeY,1

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 image exist(x) then delete image x
      if sprite exist(x) then delete sprite x
   next x

`delete anything thats left in the video memory - if anything
   flush video memory

return

`store tile data at the end of the program so its out of the way
data 10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10
data 10, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 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, 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, 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, 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, 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, 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, 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, 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, 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, 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, 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, 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, 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, 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, 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, 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, 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, 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, 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, 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, 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, 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, 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, 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, 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, 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, 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, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,10
data 10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10

+ Code Snippet

`****************************************************************************************
`**************************** 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.

`rem out along with the ending one to execute this program
remstart

`gosubs are here instead of actual code, just to make things look neat
gosub screensetup
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

   `call our home made function for displaying the tiles
   PasteTiles()

   gosub displayplayer

   `update screen
   sync

loop



gosub cleanup

`end the program
end



`****************************************************************************************
`************************************* End of program ***********************************
`****************************************************************************************



screensetup:

   `delete anything stored in video memory
   flush video memory

   `set screen resolution
   set display mode 800,600,32

   `setup syncing
   sync on
   sync rate 150

return



createimages:

   `create a green box
   cls rgb(0,255,0)
   get image 1,0,0,40,40,1

   `create a yellow box as the player
   cls rgb(255,255,0)
   get image 2,0,0,40,40,1

   `create a red box
   cls rgb(255,0,0)
   get image 10,0,0,40,40,1

   `create a blue box
   cls rgb(0,0,255)
   get image 11,0,0,40,40,1

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(20,15)

   `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 14

      for x = 0 to 19

         read TileMap(x,y)

      next x

   next y

return



makeplayer:

   `store predefined coordinates of player
   x1 = 380
   y1 = 280

   `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 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
   if leftkey()  = 1 then x1 = x1 - 2
   if rightkey() = 1 then x1 = x1 + 2
   if upkey()    = 1 then y1 = y1 - 2
   if downkey()  = 1 then y1 = y1 + 2

return



collision:

   `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 / 40)
   RightTileNum  = int((x1 + 39) / 40)
   `gets which tiles the current top and bottom co-ordinates of the player are on
   TopTileNum    = int(y1 / 40)
   BottomTileNum = int((y1 + 39) / 40)

   `gets which tiles the old left and right co-ordinates of the player are on
   OldLeftTileNum   = int(oldx1 / 40)
   OldRightTileNum  = int((oldx1 + 39) / 40)
   `gets which tiles the old top and bottom co-ordinates of the player are on
   OldTopTileNum    = int(oldy1 / 40)
   OldBottomTileNum = int((oldy1 + 39) / 40)


   `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
   if TileMap(OldLeftTileNum, TopTileNum)        >= 10 then y1 = oldy1

   `checks for top-right collision point
   if TileMap(RightTileNum,    OldTopTileNum)    >= 10 then x1 = oldx1
   if TileMap(OldRightTileNum, TopTileNum)       >= 10 then y1 = oldy1

   `checks for bottom-left collision point
   if TileMap(LeftTileNum,    OldBottomTileNum)  >= 10 then x1 = oldx1
   if TileMap(OldLeftTileNum, BottomTileNum)     >= 10 then y1 = oldy1

   `checks foe bottom-right collision point
   if TileMap(RightTileNum,    OldBottomTileNum) >= 10 then x1 = oldx1
   if TileMap(OldRightTileNum, BottomTileNum)    >= 10 then y1 = oldy1

return



displayplayer:

   `display sprite
   sprite 1,x1,y1,2

   `show frame rate (also sometimes its useful to display debug info like player
   `player positions, program specific variables etc)
   text 10,10,str$(screen fps())

return



cleanup:

   `delete any media involved in this program
   for x = 1 to 11
      if image exist(x) then delete image x
      if sprite exist(x) then delete sprite x
   next x

   `delete anything thats left in the video memory - if anything
   flush video memory

return



`this is a simple user defined function - all it does is paste the tile images to the
`screen in the correct order from the array
function PasteTiles()

   for y = 0 to 14

      for x = 0 to 19

         paste image TileMap(x,y),x*40,y*40

      next x

   next y

endfunction




`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, 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, 1,10
data 10, 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, 1,10
data 10, 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, 1,10
data 10, 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, 1,10
data 10, 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, 1,10
data 10, 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, 1,10
data 10, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,10
data 10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10

`rem out this along with the starting one to execute this program
remend













`****************************************************************************************
`**************************** HOW TO SCROLL A TILE BASED MAP ****************************
`****************************          by pizzaman           ****************************
`**************************** Date:             11/7/04      ****************************
`**************************** Time to complete: 30 mins      ****************************
`****************************************************************************************

`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:

   `delete anything stored in video memory
   flush video memory

   `set screen resolution
   set display mode 800,600,32

   `setup syncing
   sync on
   sync rate 150

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
   box 0,0,TileSizeX,TileSizeY,rgb(0,255,0),rgb(0,225,0),rgb(0,225,0),rgb(0,200,0)
   get image 1,0,0,TileSizeX,TileSizeY,1

   `create a yellow/orange box as the player
   box 0,0,TileSizeX,TileSizeY,rgb(255,255,0),rgb(255,128,0),rgb(255,128,0),rgb(255,255,0)
   get image 2,0,0,TileSizeX,TileSizeY,1

   `create a red box
   cls rgb(255,0,0)
   get image 10,0,0,TileSizeX,TileSizeY,1

   `create a blue box
   box 0,0,TileSizeX,TileSizeY,rgb(0,0,255),rgb(0,0,225),rgb(0,0,225),rgb(0,0,200)
   get image 11,0,0,TileSizeX,TileSizeY,1

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 image exist(x) then delete image x
      if sprite exist(x) then delete sprite x
   next x

   `delete anything thats left in the video memory - if anything
   flush video memory

return




`store tile data at the end of the program so its out of the way
data 10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10
data 10, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 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, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,10
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pizzaman

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ConorH

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Posted: 3rd Jan 2005 06:20

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hey thanks looks like you might have solved my problem.

its my new rat tail dog!

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Tapewormz

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Posted: 17th Jan 2005 09:08 Edited at: 17th Jan 2005 09:11

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Hey pizzaman, what do you think of this idea I posted. Is this the same thing you're doing here? I'm checking 5 directions instead of 4. The method I proposed offers the abillity to have angles, curves and other irregular collision surfaces.

http://forum.thegamecreators.com/?m=forum_view&t=46069&b=4

MILKSHAPE3D VIDEO TUTORIALS
http://www.planetquake.com/polycount/cottages/blackboard/tutorials.htm

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pizzaman

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Posted: 17th Jan 2005 20:42 Edited at: 18th Jan 2005 00:24

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Hi Tapewormz

I'm a bit confused as to how your theory works, could you elaborate on it.

The way I usually do my collision (which is not in the supplied code above - as I thought it would confuse people), is have a memblock with all your tile data in it. This data is used to draw the tiles to the screen and acts as which areas that are passable or not. Using your current and old (previous loop) player co-ordinates, you can distinguish what direction they moved in, and whether they are now on an impassable tile.
If they are on an impassable tile you can find out whether its x, or y, or both ordinates that caused the new player's position to be on an impassable tile and take the appropiate action by considering which direction they moved in.

Also though to allow more than just square based collision, you can have a list of tiles with specific collision routines and have them act however you want them to, say for ramps in a 2D platformer etc.

Hope that explains something

ATM I'm working on a 2D Tile Mapper/Level Editor, and once made I'll be able to show off some programs. It's only about 5% done at most, but looks very professional and is working at a basic level. Hopefully by March I'll be able to show it off, along with some collision routines, although that might be a bit optimistic.

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Tapewormz

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Posted: 18th Jan 2005 10:01 Edited at: 18th Jan 2005 10:01

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Well I use two arrays to hold the x and y pixel locations of where a sprite would be pasted if it was incontact with that tile at that x,y coord. Then you would apply your jumping and so on based on that. This would allow for curved collision, angles and irregular collisions with tiles.

So 100 8x8 sprites would be dimensionised as:
Dim tilex(99,8) as integer
Dim tiley(99,8) as integer

I'll code an example and come back.

MILKSHAPE3D VIDEO TUTORIALS
http://www.planetquake.com/polycount/cottages/blackboard/tutorials.htm

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pizzaman

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Posted: 18th Jan 2005 10:55 Edited at: 18th Jan 2005 23:10

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I get what your saying now. Basically your applying a kind of pixel perfect collision to your tiles, at certain collision points on the tile you move the player by a certain amount of pixels in the desired directions - if I'm reading this correctly. The only small problem with that method is that you would be using a lot of memory especially if your maps were larger. Infact this is the method I was thinking about using.

The other method I thought up was to apply simple mathematical rules to the tiles for collision - it works great for straight ramps, however it might be processor intensive for curved collisions due to use of sin,cos,tan to define the curve - altough curves can be approximated pretty well with multiple straight lines. This method would be fractionally slower than yours, but does use less memory.

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Tapewormz

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Posted: 19th Jan 2005 07:12 Edited at: 19th Jan 2005 07:25

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It doesn't use very much memory at all actually. Alot of games will have 512 tiles or less. It might take up 64K or so at the most for the collision. That's not a whole lot of memory, not at all.

It's not processor intensive at all, all the program is doing is moving the sprite along a pre-determined path. The path is the collision zone for each tile. Since most of these tiles will be repeated over and over again, it won't take up alot of memory because the angle tile and the strait tile's will be repeated hundreds of times and that's only a few bytes.

It's also not using any math for collision. It's just an invisable path for each tile.

I'll upload a snipit that show's how this method works. Basically, I got the idea by examining the method in which Tankoid's used it's collision.

MILKSHAPE3D VIDEO TUTORIALS
http://www.planetquake.com/polycount/cottages/blackboard/tutorials.htm

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pizzaman

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Posted: 19th Jan 2005 08:52

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I fully understand your method, so you don't have to upload a snippet, unless you want to of course

. Yeah your right about the memory, my mistake (wasn't thinking properly

), however to lower the memory usage further you should use an array of UDT's and declare the collision parts as bytes, or use memblocks.

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Tapewormz

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Posted: 20th Jan 2005 09:24 Edited at: 20th Jan 2005 09:24

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Yeah, I'm sure that alot of optimisation could be done to the idea that I haven't touched on yet. I'm sure there are better methods, but this one. I'm gonna look into optimisation like you suggested. Using bytes would work great, assuming that all the tiles are under 255x255 in size. I imagine that they would be no larger than 255x255.

You said you're working on a tile based map editor? I've got some good suggestions for one if you're working on one.

MILKSHAPE3D VIDEO TUTORIALS
http://www.planetquake.com/polycount/cottages/blackboard/tutorials.htm

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pizzaman

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Posted: 20th Jan 2005 11:37

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Good luck with the collision, I'm sure you'll make it fast and efficient. Actually you've intrigued me with this, I might have a go later on. Keep me up to date on this please.

Yeah I am making a tile based map editor, at the moment I have 4-5 sides of A4 paper on all the features I have planned. Could you email me the suggestions you have, its just I don't want any features posted until I can get my demo out (March roughly), and make a WIP thread for feedback and suggestions.

Its been good bouncing ideas around with you, o and btw I like some of your art on deviant, especially your most recent piece - I take it your some sort of artist?

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2D All the way! / 2d Collison advice