Walking on Sprites

[kevin]

 Walking on Sprites


  This example sets up a simple sprite scene than uses the RayHitSprite function to position a 'character' on top them.

PlayBASIC Code: [Select]

   setfps 75

   // Make images
      
   Image_FloorBlock=NewFxImage(2,10)
   rendertoimage Image_FloorBlock
   Box 0,0,100,100,true
   rendertoscreen   


   // --------------------------------------------------------------------------------
   // make a sprite scene,  these will be a set of spirtes aligned along a sinus wave 
   // --------------------------------------------------------------------------------
   AngleStep#=10   
   Xstep=20
   Radius=60
   Ypos=GetScreenHeight()/2

   X1=0
   Y1=Ypos+SinRadius(Angle#,Radius)

   for xlp=Xstep to 2000 step XStep

      Angle#=Angle#+AngleStep#
      X2=Xlp
      Y2=Ypos+SinRadius(Angle#,Radius)
      Y2=Y2+CosRadius(Angle#*3,Radius/2)

      ThisSprite=MakeAlignSpRiteToPOints(x1,y1,x2,y2,IMage_floorBlock)

      x1=x2
      y1=y2
         
   next




   // --------------------------------------------------------------------------------


      ; player variables   
      playerX#=300
      PLayerY#=100
      PLayerRadius#=25
   

   ; create camera to view the scene
      CreateCamera 1
   

   // --------------------------------------------------------------------------------
   //  Main Loop
   // --------------------------------------------------------------------------------

Do

   
   // init capture to scene mode
   CaptureToScene

   // clear the scene buffer of any old data
   ClsScene

   // capture the sprites to the scene
   drawallsprites


   // Run ray intersection against the entire sprite set
   // now __obviously___ you wouldn''t do this is real life..

   if leftkey() then playerx#=playerx#-2
   if rightkey() then playerx#=playerx#+2


   x1#=PLayerX#
   y1#=PLayerY#
   x2#=PLayerX#
   y2#=PLayerY#+(PLayerRadius#*2)

   capturedepth 2
   linec x1#,y1#,x2#,y2#,rgb(0,255,0)
   
   ThisSprite=GetFirstSprite()
   Collision=False
   While ThisSprite>0

      if RayHitSprite(x1#,y1#,x2#,y2#,ThisSprite)
         x2#=GetIntersectX#(2)                        
         Y2#=GetIntersectY#(2)-1                        
         circle x2#,y2#,5,false      
         Collision=true
      endif
   
      ThisSprite=GetNextSprite(ThisSprite)
   EndWhile   
         
   if Collision=False
      PlayerY#=PlayerY#+1
   else
      dist#=(y2#-y1#)
      if Dist#>PLayerRadius#
         PlayerY#=PlayerY#+1
      else
         PLayerY#=y2#-PlayerRadius#
      endif   
   endif   
   
   circlec playerx#,playery#,playerradius#,true,$ff0000      

   PositionCamera 1,PLayerX#-GetScreenWidth()/2,PlayerY#-GetScreenHeight()/2
   

   drawcamera 1

   Sync

loop
      


Function MakeAlignSpriteToPOints(x1,y1,x2,y2,CollisionIMage)

   ThisSprite=NewSprite(x1,y1,CollisionIMage)
   SpriteDrawMode ThisSprite,2
   positionSpriteZ ThisSprite,50

   tw#=GetImageWidth(CollisionImage)
   th#=GetImageHeight(CollisionImage)

   dist#=GetDistance2d(x1,y1,x2,y2)
   ScaleSpriteX ThisSprite,Dist#/tw#   
   angle#=getangle2d(x1,y1,x2,y2)
   rotateSprite ThisSPrite,Angle#


   SpriteCollisionMode 1,1  ;(collision mode is rotated rectangles)
      
EndFunction ThisSprite

Related Examples

  Walking on Sprite Collision Map
  Platformer Pixel Collisions Via Ray Casting
  Advanced Platform Collision (Vector WORLD)

[ATLUS]

nice exampale ;)

[micky4fun]

Hi Kevin

well been trying to muck about with this type of collision as i like the look of it ,
can you tell me why the code below works when spritecollisonmode is set to 1 , but line falls short of ground , so no good for pixel pefect
but when changing spritecollisonmode is set to 6 , pixel perfect it does not work , returns RayX2 and RayY2 as 0
am i missing something , or is there another easy way to do this as pixel perfect

PlayBASIC Code: [Select]

     loadfximage "ground.png",10

     spr=getfreesprite()
     CreateSprite Spr
     PositionSprite Spr,0,600
     SpriteImage Spr,10
     SpriteCollisionMode Spr,1
  
; Init the Rays Starting Point
  RayX1=100
  RayY1=100
  
  Do
     Cls RGB(0,0,0)
   
     RayX2=MouseX()
     RayY2=MouseY()
     
        If RayHitSprite(RayX1,RayY1,rayX2,rayY2,Spr)=true
           RayX2=GetIntersectX#(0)
           RayY2=GetIntersectY#(0)
        EndIf
        
     Line RayX1,RayY1,RayX2,RayY2
     DrawAllSprites
     Sync
  Loop

thanks
mick :)

ground image im using attached

[kevin]

am i missing something

Yes, Ray intersection is for vector collision, not pixels.. 

[micky4fun]

Ok thanks Kevin

thats ashame , ile continue messing about with this for a little longer and see what happens

mick :)

[kevin]

 
If the target object doesn't need rotation, then you can get a reasonable  approximation  as follows.

PlayBASIC Code: [Select]

   openscreen 1024,768,32,1

   loadfximage "E:\Downloads\ground.png",10

   spr=getfreesprite()
   CreateSprite Spr
   PositionSprite Spr,0,600
   SpriteImage Spr,10
   SpriteCollisionMode Spr,1
  
; Init the Rays Starting Point
  RayX1=300
  RayY1=300
  
  Do
     Cls RGB(0,0,0)
   
     RayX2=MouseX()
     RayY2=MouseY()

     DrawAllSprites

     
        If RayHitSprite(RayX1,RayY1,rayX2,rayY2,Spr)=true

            ThisImage=getSpriteImage(Spr)
            ImageXpos=GetSpritex(Spr)
            ImageYpos=GetSpritey(Spr)

            Collision,impactx#,impacty#=Plot_Ray_Over_image(Rayx1,Rayy1,Rayx2,Rayy2,ThisImage,ImageXpos,ImageYpos)

            if Collision
                  rayx2=impactx#            
                  rayy2=impacty#            
            

                  Circle Rayx2,Rayy2,5,false
            endif

;           RayX2=GetIntersectX#(0)
 ;          RayY2=GetIntersectY#(0)
        EndIf
        
     Line RayX1,RayY1,RayX2,RayY2
     Sync
  Loop




Function Plot_Ray_Over_image(Rayx1#,Rayy1#,Rayx2#,Rayy2#,ThisImage,ImageXpos,ImageYpos)

      width      =getimagewidth(Thisimage)
      height   =getimageheight(Thisimage)

      Collision=False
                     
      Result=LineIntersectRect(Rayx1#,Rayy1#,Rayx2#,Rayy2#,ImageXpos,ImageYpos,ImageXpos+Width,ImageYpos+height)
              
      if result>-1

         if Result=1
            Rayx1#=GetIntersectX#(0)
            Rayy1#=GetIntersectY#(0)
            Rayx2#=GetIntersectX#(1)
            Rayy2#=GetIntersectY#(1)
         endif
         
            ;linec Rayx1#,Rayy1#,Rayx2#,Rayy2#,255

            dist#=getdistance2d(Rayx1#,Rayy1#,Rayx2#,Rayy2#)
            dx#=Rayx2#-Rayx1#
            dy#=Rayy2#-Rayy1#

            if dist#<>0
               nx#=dx#/dist#      
               ny#=dy#/dist#      
            else
               nx#=0
               ny#=0
            endif            

            OldSurface=GetSurface()
            rendertoimage ThisImage
               lockbuffer

                  Transparentcolour=GetImageMaskCOlour(ThisImage)

                  for lp=0 To int(Dist#)
               
                     x#=rayx1#+(nx#*lp)
                     y#=rayy1#+(ny#*lp)

                     x#=x#-ImageXpos
                     y#=y#-ImageYpos
                     if point(X#,y#)<>Transparentcolour

                        Impactx#=x#+ImageXpos                        
                        Impacty#=y#+ImageYpos                        
                        Collision=true                     
                        exitfor
                     endif

      
                  next      
               unlockbuffer
            rendertoimage OldSurface
      endif


EndFunction  Collision,ImpactX#,ImpactY#




 

    Note:  - Today i'd recommend using the RayToMap pixel collision functions

[micky4fun]

Hi Kevin

yes nice one , this looks good , will av a bit more time later today to get into this a bit deeper see what i can come up with

thanks
mick :)