Sprite Collision With An Image Mask

[kevin]

Sprite Collision With An Image Mask

  This example shows how you can use ImageHitSpritePixels for pixel based collision against a collision mask.  

PlayBASIC Code: [Select]

   sw=GetScreenWidth()
   sh=GetScreenHeight()

   global CollisionMask=NewFXIMage(sw,sh)
   
   // Draw some circles for some collision hot spots
   rendertoimage CollisionMask
   for lp=0 to 50
      circle rnd(sw),rnd(sh),50,true
   next
   
   // clear our a chunk where the player is going to be dropped
   circlec sw/2,sh/2,100,true,rgb(0,0,0)
   

   ; Create player image.. In this demo the player is a blue circle
   PlayerImage=newFXImage(64,64)
   rendertoimage PlayerImage   
   circlec 32,32,32,true,255
   rendertoscreen

   ; Create player sprite
   PlayerSpeed#=5
   PLayer=NewSprite(sw/2,sh/2,PLayerImage)
   SpriteDrawMode PLayer,2
   SpriteCollisionMode Player,6
   SpriteCollisionDebug Player,off
   

   ; Main loop
   Setfps 60   
   Do
      ; set the cursor
      setcursor 0,0

      ; Draw the backdrop
      c1=rgb(20,230,140)
      c2=rgb(120,30,40)
      shadebox 0,0,sw,sh,c1,c2,c1,c2

      ; Draw the collision Mask image so we can see what we're hitting
      DrawImage CollisionMask,0,0,true

      ; handle moving the player
      MoveX#=(Leftkey()*-PLayerSpeed#) + (Rightkey()*PlayerSpeed#)
      MoveY#=(Upkey()*-PLayerSpeed#) + (Downkey()*PlayerSpeed#)
      MOveMe(Player,MoveX#,MoveY#)

      ; draw the sprites   
      drawAllSprites
      
      ; refresh the screen and loop back to the DO statement.
      Sync
   loop


Function MOveMe(ThisSprite,MoveX#,MoveY#)
      SpriteTint ThisSprite,$ffffff   

      if Movex#=0 and Movey#=0 then exitfunction

      // Get it's current position
      BaseX#=GetSpriteX(ThisSprite)
      BaseY#=GetSpriteY(ThisSprite)
      x#=BaseX#+MoveX#
      y#=BaseY#+MoveY#
      positionSprite ThisSprite,x#,y#


      ; Check if this position hits the collision mask      
      if ImageHitSpritePixels(CollisionMask,0,0,ThisSprite,1)  
         SpriteTint ThisSprite,rndrgb()   
         
         // iof it did, try and resolve       
         dist=GetDistance2d(0,0,movex#,movey#)
         if Dist>0
            nx#=moveX#/dist
            ny#=movey#/dist
         
            X#=BaseX#
            Y#=BaseY#
            for lp=1 to Dist 
               positionSprite ThisSprite,Basex#+(lp*nx#),Basey#+(lp*ny#)
               if ImageHitSpritePixels(CollisionMask,0,0,ThisSprite,1)=true
                  x#=Basex#+((lp-1)*nx#)
                  y#=Basey#+((lp-1)*ny#)
                  exitfor
               endif
            next
         endif
         positionSprite ThisSprite,x#,y#
      endif

EndFunction

  Notes:

       * This is old code, It's generally a better idea to use MAPS today.   CircleHitMap / CircleHitMapPixels commands added to  PlayBASIC V1.64N2 / V164N3 (Work In Progress) Gallery