Tile Map Collision

[iCon]

I'm struggling to get tile map collision detection in a basic platformer I'm attempting. I'm using sprvel.

[Darkjester]

use the sprleft() sprright() sprtop() sprbottom() functions to return the position of the sprite..

[iCon]

I can do basic collision detection, I just need a way to find each tile and check for collision without slowing down the program from lots of tiles.

[matthew]

Davy wrote a Program here some time ago which uses Tilemap Collision in a game like Zelda.

I've put the code & textures in a Zip file that you can download here.

[iCon]

Can't see how I would apply this to individual tile collision, that program uses a constant to check the collision with the side of the game. My aim is for the sprite(s) to collide with each specified tile. I need a way to find each tiles x and y values and use this to collide the sprite with them by cycling through each tile.

e.g. for j = 0 to 3
for i = 0 to 11
if tiles (i) (j) = 1 then
collide
endif
next
next

[matthew]

Try taking a look at the example here by DJLinux.

[iCon]

Excellent, but I'm having a some trouble trying to apply to my program. I understand how it works but I can't seem to get it to work. I don't know what is wrong.

Use your own sprite atm.

textmode (TEXT_BUFFERED)

data 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
data 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
data 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
data 1, 1, 1, 1, 2, 2, 2, 1, 1, 0, 1, 1
data 0, 0, 1, 1, 2, 2, 2, 1, 1, 0, 1, 1
data 0, 1, 1, 1, 1, 2, 1, 1, 0, 0, 1, 1
data 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 1
data 0, 0, 1, 1, 0, 1, 1, 0, 0, 0, 0, 0
data 0, 0, 1, 1, 1, 0, 1, 0, 0, 0, 0, 0

dim xtiles = 11, ytiles = 8
dim x, y, tiles (xtiles) (ytiles), tilemap

for y = 0 to ytiles
   for x = 0 to xtiles
       read tiles (x) (y)
   next
next

tilemap = newtilemap (loadtexstrip ("tiles\tiletest.png", 64, 64))
sprsetsolid (false)
sprsetxrepeat (false)
sprsetyrepeat (false)
sprsetpos (128, 192)'both variables are divisible by the tiles height and width
sprsettiles (tiles)

'tilemap variables
dim tloop 'tile map loop
dim i, j, m

'constants
const widthhalf = 20
const heighthalf = 60

'variables
dim character (texstripframes ("characterfile")- 1)

dim walk (9), stand
dim score = 0
dim a = 1
dim ploop 'platform loop
dim cl 'collision loop
dim notonplat = 1
dim onground = false
dim newplatform = true

'player variables
dim xplayer = 175
dim yplayer = 200

'collision variables
dim xmap, ymap

character = loadtexstrip ("character")

stand = character (0)

walk (0) = character (8)
walk (1) = character (1)
walk (2) = character (2)
walk (3) = character (3)
walk (4) = character (4)
walk (5) = character (0)
walk (6) = character (5)
walk (7) = character (6)
walk (8) = character (7)
walk (9) = character (0)

dim sprite
sprite = newsprite (stand)
sprsetpos (xplayer, yplayer)

'collision function
function notcollision (xloc, yloc)'x location, y location
   'left and right
   ymap = yloc/64
   xmap = (xloc - widthhalf)/64       'right side of sprite
   if tiles (xmap, ymap) = 1 then
       return false
   endif
   xmap = (xloc + widthhalf)/64       'left side of sprite
   if tiles (xmap, ymap) = 1 then
       return false
   endif
   'top and bottom
   xmap = xloc/64
   ymap = (yloc - heighthalf)/64       'top of sprite
   if tiles (xmap, ymap) = 1 then
       return false
   endif
   ymap = (yloc + heighthalf)/64       'bottom of sprite
   if tiles (xmap, ymap) = 1 then
       return false
   endif
   return true
end function

while true
   'Player Control
   bindsprite (2)
   if scankeydown (VK_RIGHT) then
       sprsettextures (walk)
       sprsetanimspeed (0.2)
       sprsetxflip (false)
       xplayer = xplayer + 1
   elseif scankeydown (VK_LEFT) then
       sprsettextures (walk)
       sprsetanimspeed (0.2)
       sprsetxflip (true)
       xplayer = xplayer - 1
   else
       sprsettexture (stand)
       xplayer = xplayer
   endif
   
   'Stops the player going off screen
   if sprleft (2) <= -10 and scankeydown (VK_LEFT) then
       xplayer = xplayer + 1
   endif
   
   if sprright (2) >= spriteareawidth () + 10 and scankeydown (VK_RIGHT) then
       xplayer = xplayer - 1
   endif
   
   'Tilemap Collision Detection
   if notcollision (xplayer, yplayer) = true then
       print "gravity"
   endif
   
   yplayer = yplayer + 1 'temporary, just to check for collision

   bindsprite (2): sprsetpos (xplayer, yplayer)
   drawtext ()
   animatesprites ()
   waittimer (10)
wend


Attachments:

[matthew]

You can download a ZIP file here with my corrections. There is still something wrong with the game which I haven't got around to fixing which is the Tiles on the the Screen don't appear to match their DATA value. So the Character falls through tiles which he shouldn't. If I had more time I'd have been able to correct it completely but you should be able to finish it off.

[shadow008]

Ya know, I would post the thread that references my 2D ninja demo (which I'm sure some members here may remember), but I cant find the thread anywhere on these forums. Musta gotten deleted. So anyways, this is a 2D platform style game I never gotten around to finishing (I would probably rewrite it before going off that code >.>), but it still works for demonstration purposes.

Going down to line 495 theres this thing labled "physics" (again, sloppy code (also note improper use of the term "acceleration)) - This is where my collision detection starts.

First off, since it is a static tile based game, you will always know the boundary's of the box's(tiles). Since your image has a static width and a static height, if you know the position of your image(sprite,animation,ect.), you have the boundary of your image. If those two boundary's EVER collide, make them NOT collide (simple, right?) Heres the example from my code:


'test for "on ground" status
       if tiles(((player(i).y+16)/32),(player(i).x+3)/32) = 1 or tiles(((player(i).y+16)/32),(player(i).x-3)/32) = 1 then
           player(i).onground = true
           sprsetpos(sprx(),player(i).heightlevel*32+16)
           player(i).yhit = true


Now whats happening here? Well, my tiles are set up in an array... HOW CONVENIENT! By knowing that all tiles are 32 pixles by 32 pixles, I now have relative 2D location, and boundary box. So i have a say 640x480 screen, that means i can fit 20x15 tiles in the window (and more if i wanted a larger SPRITE AREA SIZE; which is absolutely _*NOT*_ the same as screen resolution, and is changed by the function ResizeSpriteArea(real,real) )

So cool, I know the tile positions easily, for example tile 2,4 will have location _TileCount*TileSize-HalfTileSize_ or 2*32-16,4*32-16 = 48,112 to the CENTER of the tile. Finding its top most part is as simple as negating the -16 on the y axis and the bottom most part it would be changed to -32. And the same for the x axis (oh yeah, the sprites are set from the top LEFT corner so + on the Y axis is DOWN)

Now for the character collision...

So I have the Box boundary, well, the character is quite simply, the EXACT same process, with a different center point. Your character boundary is simple as taking the position of your character, dividing it by however big your tile size is, and casting it into an integer rounded DOWN(if it isnt already one). So a character at position 478,133 would be at int(478/32),int(133/32) or 14,4. Well, now you know which tiles to check(all this assuming your character isnt bigger than any tiles). Only the ones corresponding to +/-1 on each axis. So only tiles 15,4 13,4 14,5 and 14,3 must be checked. However, its even simpler if your tiles are in an array like mine are in the demo(and as are yours). Here, you only have to take your character position, and add +HALF_CHARACTER_HEIGHT(in pixles) on each axis, and then cast that into an integer.

So lets say we have a character thats 8x32 pixles (like mine are in the demo), At position 478,133 we only need one more step then described above. Instead of simply dividing by tile size and casting into an int, we do something like int(478+4/32) (adding half the character width size) - which equates to 15. Well, now its really as simple as checking IN YOUR ARRAY, the tile at position 15,4. So it boils down to something really as simple as: If tiles(15)(4) <> 0 then... Also note, im using 0 because its what u have in ur code for "nothing".

Thats it, thats really a simple concept once you get use to it. I have no more time to continue, so if you have further questions, just post

Good luck with your project!

Attachments:

[matthew]

Thanks for uploading the file, I knew that someone had created a Platformer before but I couldn't find it on the forum.

[shadow008]

Feb 23, 2012 16:32:23 GMT -5 matthew said:

Thanks for uploading the file, I knew that someone had created a Platformer before but I couldn't find it on the forum.

No problem But seriously, that entire thread like... disappeared... magically...

[matthew]

Well I know when DJLinux became a Mod he deleted several years worth of threads.

So sad to say but it was probably one of those.

[iCon]

I've got it working, kinda.
Whenever I try to add/subtract half the sprites width/height for the collision detection, it doesn't work. If I leave widthhalf and heighthalf at 0, it works just with the centre of the sprite.
I've removed left/right collision until I get the down collision working.
Sprite is included below.


textmode (TEXT_BUFFERED)

'    0  1  2  3  4  5  6  7  8  9 10 11 12
data 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0                   '0
data 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0                   '1
data 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0                   '2
data 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0                   '3
data 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0                   '4
data 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0                   '5
data 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1                   '6
data 1, 1, 1, 1, 2, 2, 2, 1, 1, 0, 1, 1, 1                   '7
data 0, 0, 1, 1, 2, 2, 2, 1, 1, 0, 1, 1, 1                   '8
data 0, 1, 1, 1, 1, 2, 1, 1, 0, 0, 1, 1, 1                   '9
data 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 1, 0                   '10
data 0, 0, 1, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0                   '11
data 0, 0, 1, 1, 1, 0, 1, 0, 0, 0, 0, 0, 0                   '12
data 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0                   '13
data 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0                   '14

dim xtiles = 12, ytiles = 14
dim x, y, tiles (xtiles) (ytiles), tilemap

for y = 0 to ytiles
   for x = 0 to xtiles
       read tiles (x) (y)
   next
next

tilemap = newtilemap (loadtexstrip ("tiles\tiletest.png", 64, 64))
sprsetsolid (false)
sprsetxrepeat (false)
sprsetyrepeat (false)
sprsetpos (0, 0)
sprsettiles (tiles)

'tilemap variables
dim tloop 'tile map loop
dim i, j, m

'constants
const widthhalf = 0
const heighthalf = 0

'variables
dim cyanman (texstripframes ("tiles\cyanman.png")- 1)

dim walk (9), stand
dim score = 0
dim a = 1
dim ploop 'platform loop
dim cl 'collision loop
dim notonplat = 1
dim onground = false
dim newplatform = true

'player variables
dim xplayer# = 175
dim yplayer# = 100

'collision variables
dim xmap, ymap

cyanman = loadtexstrip ("tiles\cyanman.png")

stand = cyanman (0)

walk (0) = cyanman (8)
walk (1) = cyanman (1)
walk (2) = cyanman (2)
walk (3) = cyanman (3)
walk (4) = cyanman (4)
walk (5) = cyanman (0)
walk (6) = cyanman (5)
walk (7) = cyanman (6)
walk (8) = cyanman (7)
walk (9) = cyanman (0)

dim sprite
sprite = newsprite (stand)
sprsetpos (xplayer#, yplayer#)

'collision function
function notcollision (xloc, yloc)'x location, y location
   'top and bottom
   xmap = (xloc/32)
   ymap = ((yloc - heighthalf)/32)       'top of sprite
   if tiles (xmap, ymap) = 1 then
       return false
   endif
   ymap = ((yloc + heighthalf)/32)      'bottom of sprite
   if tiles (xmap, ymap) = 1 then
       return false
   endif
   return true
end function

while true
   cls
   'Player Control
   bindsprite (2)
   if scankeydown (VK_RIGHT) then
       sprsettextures (walk)
       sprsetanimspeed (0.2)
       sprsetxflip (false)
       xplayer# = xplayer# + 1
   elseif scankeydown (VK_LEFT) then
       sprsettextures (walk)
       sprsetanimspeed (0.2)
       sprsetxflip (true)
       xplayer# = xplayer# - 1
   else
       sprsettexture (stand)
       xplayer# = xplayer#
   endif
   
   'Stops the player going off screen
   if sprleft (2) <= -10 and scankeydown (VK_LEFT) then
       xplayer# = xplayer# + 1
   endif
   
   if sprright (2) >= spriteareawidth () + 10 and scankeydown (VK_RIGHT) then
       xplayer# = xplayer# - 1
   endif
   
   'Tilemap Collision Detection
   if notcollision (xplayer#, yplayer#) = true then
       yplayer# = yplayer# + 1
   endif
   
   locate 0, 1: print xmap
   locate 0, 3: print ymap
   bindsprite (2): sprsetpos (xplayer#, yplayer#)
   drawtext ()
   animatesprites ()
   waittimer (10)
wend


Attachments:

[matthew]

Try using SprSetXCentre & SprSetYCentre to adjust the centre of the Sprite.

You'll find the commands described in the Sprite Library Guide.

[shadow008]

Your problems atm:

Change line "tilemap = newtilemap (loadtexstrip ("tiles\tiletest.png", 64, 64))"

to

tilemap = newtilemap (loadtexstrip ("tiles\tiletest.png", 32, 32))

OR change the half height to 32. I'd make a constant for your tile size.

ALSO: Add some changes like this to your code:

-Make a definite tile size like CONST TileSize = 32
...
tilemap = newtilemap (loadtexstrip ("tiles\tiletest.png", TILE_SIZE, TILE_SIZE))

-Make a definite screen size using:
ResizeSpriteArea(640,480)
OR
ResizeSpriteArea(xtiles*TILE_SIZE,ytiles*TILE_SIZE)

-Make xtiles and ytiles either EQUAL or in proportion to the screen size

So something like 20x15 tiles for 640x480 sprite size.

-Change the zorder of your tiles to be behind your character:

tilemap = newtilemap (loadtexstrip ("tiles\tiletest.png", 64, 64))
sprsetsolid (false)
sprsetxrepeat (false)
sprsetyrepeat (false)
sprsetpos (0, 0)
sprsettiles (tiles)
SprSetZOrder(-1)

....

tilemap = newtilemap (loadtexstrip ("tiles\tiletest.png", 64, 64))
SprSetZOrder(1)
sprsetsolid (false)
....

Then you should have no problems fixing the side to side collision, and moving further on.

Hope this helps ^_^