Tilemap Collision

BlitzMax Forums/BlitzMax Beginners Area/Tilemap Collision

po (Posted 2009) [#1]

I'm in a bit of a pickle. I'm making a platformer Commander Keen/Mario style, using an array of objects for the tiles. My problem is getting the player to accurately collide with the tiles so that he doesn't (appear to) overlap any of the tiles. Up until now I've been using this system: There's a field in TPlayer called cTile that holds the TTile object that the player's center is currently overlapping. In other words, it's the tile that the player is currently occupying. I then check if the player is overlapping the tile below him, to the right of him, to the left of him, and above him. For example: If playerY+playerHeight>tileBelowY Then playerY=tileBelowY-playerHeight This works fine for all sides, except when dealing with the edge of say, a drop-off. Where in games like Mario, the player can walk to his very heels on the edge of a drop-off, using my method the player simply falls into the tile half-way through the player, looking and playing quite poorly. So I figure the best method would be to use the CollideRect function instead. So I put CollideRect(tileX,tileY,tileWidth,tileHeight,0,1) in every tile's Draw() method, and checked for collision with the player using CollideRect(playerX,playerY,playerWidth,playerHeight,1,0) and found that I can indeed detect the collision, but I have no way of stopping the player from going through the tiles because I don't know which tile I'm colliding with. Is there a way to get which tile collided with the player? I use the function GetTile(x,y) to get tiles based off of coordinates, but coords don't help me much if I'm trying to avoid the player-on-edge-of-drop-off issue. Any ideas?

therevills (Posted 2009) [#2]

Hi Po, Heres a quick example of Tilemap collision: SuperStrict Graphics 800,600,0 SeedRnd MilliSecs() Const TILE_SIZE% = 32 Const GRAVITY# = 0.6 Const MAPWIDTH% = 800/TILE_SIZE Const MAPHEIGHT% = 600/TILE_SIZE Global map:Int[MAPWIDTH, MAPHEIGHT] Cls 'create player image SetColor 1,1,1 DrawOval 0,0,30,30 SetColor 255,255,255 DrawOval 3,3,24,24 SetColor 255,0,0 DrawOval 5,5,20,20 Global playerImg:TImage=CreateImage(30,30,1,DYNAMICIMAGE|MASKEDIMAGE) GrabImage playerImg,0,0 Cls ' create tile SetColor 100,30,0 DrawRect 0,0,16,16 DrawRect 16,16,16,16 SetColor 147,70,0 DrawRect 16,0,16,16 DrawRect 0,16,16,16 Global tile:TImage=CreateImage(TILE_SIZE,TILE_SIZE,1,DYNAMICIMAGE|MASKEDIMAGE) GrabImage tile,0,0 Cls MidHandleImage playerImg ReadLevelData() Type TSprite Field x#,y# Field dx#,dy# Field xspeed#,yspeed# Field image:TImage Field w%,h% Field w2%,h2% Method draw() DrawImage image, x, y End Method End Type Type TPlayer Extends TSprite Field jumping:Int = 0 Function Create:TPlayer(x#,y#) Local p:TPlayer = New TPlayer p.x = x p.y = y p.xspeed = 5 p.yspeed = 10 p.image = playerImg p.w = ImageWidth(playerImg) p.h = ImageHeight(playerImg) p.w2 = p.w/2 p.h2 = p.h/2 Return p End Function Method update() If KeyDown(KEY_RIGHT) Local tmpx# = x + xspeed If getTile(tmpx+w2,y+h2-1) = 0 And getTile(tmpx+w2,y-h2) = 0 And getTile(tmpx+w2,y) = 0 x = tmpx Else x = Floor(((x+w2)/TILE_SIZE)+0.5)*TILE_SIZE - w2 EndIf End If If KeyDown(KEY_LEFT) Local tmpx# = x - xspeed If getTile(tmpx-w2,y+h2-1) = 0 And getTile(tmpx-w2,y-h2) = 0 And getTile(tmpx-w2,y) = 0 x = tmpx Else x = Floor(((x-w2)/TILE_SIZE)+0.5)*TILE_SIZE + w2 EndIf End If If KeyDown(KEY_UP) And Not jumping dy = 0 - yspeed jumping = True EndIf If Not jumping If getTile(x-w2,y+h2) = 0 And getTile(x+w2,y+h2) = 0 And getTile(x,y+H2) = 0 jumping = True EndIf EndIf If jumping dy:+GRAVITY Local tmpy# = y + dy If dy<>0 If dy>0 If getTile(x-w2,tmpy+h2-1) > 0 Or getTile(x+w2-1,tmpy+h2-1) > 0 Or getTile(x,tmpy+h2-1) > 0 dy = 0 jumping = False y = Floor(((tmpy+h2)/TILE_SIZE)+0.5)*TILE_SIZE - h2 Else y = tmpy EndIf Else If getTile(x-w2,tmpy-h2) > 0 Or getTile(x+w2-1,tmpy-h2) > 0 Or getTile(x,tmpy-h2) > 0 dy = 0 y = Floor(((tmpy-h2)/TILE_SIZE)+0.5)*TILE_SIZE + h2 Else y = tmpy EndIf EndIf End If End If End Method End Type SetColor 255,255,255 SetBlend ALPHABLEND Global player:TPlayer = TPlayer.Create(100,200) While Not AppTerminate()=1 And Not KeyHit(KEY_ESCAPE) player.update() Cls DrawMap() player.draw() Flip 1 Wend Function ReadLevelData() For Local y:Int = 0 To MAPHEIGHT - 1 For Local x:Int = 0 To MAPWIDTH - 1 Local Data:Int ReadData Data map[x, y]= Data Next Next End Function Function DrawMap() For Local x:Int = 0 To MAPWIDTH - 1 For Local y:Int = 0 To MAPHEIGHT - 1 Select map[x, y] Case 1 DrawImage Tile, x * TILE_SIZE, y * TILE_SIZE End Select Next Next End Function Function getTile%(x#,y#) Return map[Floor(x/TILE_SIZE), Floor(y/TILE_SIZE)] End Function DefData 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 DefData 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1 DefData 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 1 DefData 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1 DefData 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 1 DefData 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1 DefData 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 1 DefData 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1 DefData 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1 DefData 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1 DefData 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 1 DefData 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1 DefData 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 1 DefData 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1 DefData 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 1 DefData 1, 0, 1, 0, 1, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1 DefData 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1 DefData 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 Cheers!

po (Posted 2009) [#3]

Ah, thank you.