Explode Shape

kevin · October 30, 2009, 10:01:43 AM

Explode Shape

This example explodes a shape from 2D mesh into a bunch debris styled line fragments, a bit like the old asteroids coin op.

PlayBASIC Code: [Select]

; PROJECT : Exploding_Shape
; AUTHOR  : Kevin Picone
; CREATED : 10/31/2009
; EDITED  : 10/31/2009
; ---------------------------------------------------------------------

   setfps 60


   Type tEdge
      xpos#,ypos#         ; position
      SpeedX#,Speedy#   ; movement speed
      Angle#
      RotSpeed#
      EdgeLength#         ; length of fragment
   Endtype   

   Dim Edges(100) as tEdge

   Shape =newconvexshape(50,4)
   Xpos#=400
   Ypos#=300

   do
         cls  0   

         ; draw shape to represent some game object
         rotateshape Shape,Angle#,1
         drawshape shape,Xpos#,Ypos#,1

         ; press space to explode it
         if spacekey()

               // dump this shape into the edge buffer
               ExplodeShape(Shape,Xpos#,Ypos#,Angle#,rndrange#(1,10))

               // kill the old shape and rfandomly create a new one
               deleteshape Shape
               Shape =newconvexshape(rndrange(20,100),rndrange(4,20))
               Xpos#=rnd(800)
               Ypos#=rnd(600)
               flushkeys

         endif

                  
         ProcessEdges()      

         Angle#=wrapangle(Angle#,0.25)


      Sync
   loop



Function ProcessEdges()
   Size=30
   ClipRegionX1=-Size
   ClipRegionY1=-Size
   ClipRegionX2=GetScreenWidth()+Size
   ClipRegionY2=GetScreenWidth()+Size
      
   lockbuffer
      for lp=0 to getarrayelements(edges(),1)
         // check if there's anything allocated at position in the array
         if Edges(lp)

               // move the fragments base point
               Xpos#=Edges(lp).Xpos#+Edges(lp).SpeedX#
               Ypos#=Edges(lp).Ypos#+Edges(lp).SpeedY#
               
               Edges(lp).Xpos#=Xpos#
               Edges(lp).Ypos#=Ypos#

               if pointinbox(Xpos#,ypo#,ClipRegionX1,ClipRegionY1,ClipRegionX2,ClipRegionY2)

                  Angle#=wrapangle(Edges(lp).Angle#,Edges(lp).RotSpeed#)

                  // get the size of this fragment
                  l#=Edges(lp).EdgeLength#
   
                  fx#=cosradius(angle#,l#)
                  fy#=sinradius(angle#,l#)
   
                  line Xpos#-fx#,Ypos#-fy#,Xpos#+fx#,Ypos#+fy#

                  Edges(lp).Angle#=angle#               
            else
                  Edges(lp)= Null
            endif
            
         endif   
      next
   unlockbuffer

EndFunction



Function ExplodeShape(Thisshape,Xpos#,Ypos#,Angle#,Speed#)

   for edge=0 to getshapeedges(ThisShape,1)

      if Getshapeedgestatus(ThisShape,edge)
         // edge index in the array
         Index=GetFreecell(Edges())      

         Edges(Index).Xpos#=Xpos#
         Edges(Index).Ypos#=Ypos#
         
         
         Edges(Index).RotSpeed#=rndrange#(-10,10)


         // get the       
         Vert1=GetShapeEdge(ThisShape,Edge,0)
         Vert2=GetShapeEdge(ThisShape,Edge,1)

         // Get the vert and rotate it to the current angle of the shape
         x1#,y1#=Rotate2DVertex(ThisShape,Vert1,Angle#)
         x2#,y2#=Rotate2DVertex(ThisShape,Vert2,Angle#)

      
         // midr point between 
         mx#=(x1#+x2#)/2
         my#=(y1#+y2#)/2

         dist#=getdistance2d(0,0,mx#,my#)
         if Dist#>0
            nx#=mx#/dist#         
            ny#=my#/dist#         
         else
            nx#=0
            ny#=0
         endif

         // dist from mid point to one edge of fragment..          
         Edges(Index).EdgeLength#=getdistance2d(mx#,my#,x2#,y2#)

         // Speed fragment is moving
         Edges(Index).speedX#=nx#*Speed#
         Edges(Index).speedY#=ny#*Speed#

         // mid point of line fragment
         Edges(Index).Xpos#=Xpos#+mx#
         Edges(Index).Ypos#=Ypos#+my#

         Edges(Index).Angle#=getangle2d(mx#,my#,x2#,y2#)

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Related Examples

* 8Way Layered Star Field / Asteroids Style

kevin · October 30, 2009, 10:50:57 PM

This is just a little update, the only difference really is this that version supports shape scaling as well as rotation and few a few extra comments. I've left the original just in case you don't need scaling.

PlayBASIC Code: [Select]

   setfps 60

   Type tEdge
      xpos#,ypos#         ; position
      SpeedX#,Speedy#   ; movement speed
      Angle#            ; current angle 
      RotSpeed#         ; speed this fragment is rotating
      EdgeLength#         ; length of fragment
   Endtype   

   Dim Edges(100) as tEdge


   // Create a start shape to explode 
   Shape =newconvexshape(50,4)
   Xpos#=400
   Ypos#=300
   Scale#=1

   do
         cls  0   

         scale#=2+Sin(Angle#*4)

         ; draw shape to represent some game object
         rotateshape Shape,Angle#,Scale#
         drawshape shape,Xpos#,Ypos#,1

         ; press space to explode it
         if spacekey()

               // dump this shape into the edge buffer
               ExplodeShape(Shape,Xpos#,Ypos#,Angle#,Scale#,rndrange#(1,10))

               // kill the old shape and rfandomly create a new one
               deleteshape Shape
               Shape =newconvexshape(rndrange(20,100),rndrange(4,20))
               Xpos#=rnd(800)
               Ypos#=rnd(600)
               flushkeys

         endif

         // run through and process any edge frages that may exist                  
         ProcessEdges()      

         // bump the rotation angle of the current shape
         Angle#=wrapangle(Angle#,0.25)

         // display instructions
         print "Press Space To Explode Current Shape"

      Sync
   loop



Function ProcessEdges()
   Size=30
   ClipRegionX1=-Size
   ClipRegionY1=-Size
   ClipRegionX2=GetScreenWidth()+Size
   ClipRegionY2=GetScreenWidth()+Size
      
   lockbuffer
      for lp=0 to getarrayelements(edges(),1)
         // check if there's anything allocated at position in the array
         if Edges(lp)

               // move the fragments base point
               Xpos#=Edges(lp).Xpos#+Edges(lp).SpeedX#
               Ypos#=Edges(lp).Ypos#+Edges(lp).SpeedY#
               
               Edges(lp).Xpos#=Xpos#
               Edges(lp).Ypos#=Ypos#

               if pointinbox(Xpos#,ypo#,ClipRegionX1,ClipRegionY1,ClipRegionX2,ClipRegionY2)

                  Angle#=wrapangle(Edges(lp).Angle#,Edges(lp).RotSpeed#)

                  // get the size of this fragment
                  l#=Edges(lp).EdgeLength#
   
                  fx#=cosradius(angle#,l#)
                  fy#=sinradius(angle#,l#)
   
                  line Xpos#-fx#,Ypos#-fy#,Xpos#+fx#,Ypos#+fy#

                  Edges(lp).Angle#=angle#               
            else
                  Edges(lp)= Null
            endif
            
         endif   
      next
   unlockbuffer

EndFunction



Function ExplodeShape(Thisshape,Xpos#,Ypos#,Angle#,Scale#,Speed#)

   for edge=0 to getshapeedges(ThisShape,1)

      if Getshapeedgestatus(ThisShape,edge)
         // edge index in the array
         Index=GetFreecell(Edges())      

         Edges(Index).Xpos#=Xpos#
         Edges(Index).Ypos#=Ypos#
         
         
         Edges(Index).RotSpeed#=rndrange#(-10,10)


         // get this edges vertex pair that's using
         Vert1=GetShapeEdge(ThisShape,Edge,0)
         Vert2=GetShapeEdge(ThisShape,Edge,1)

         // Get the verts and rotate them to the current angle of the shape
         x1#,y1#=Rotate2DVertex(ThisShape,Vert1,Angle#,Scale#)
         x2#,y2#=Rotate2DVertex(ThisShape,Vert2,Angle#,Scale#)

      
         // mid point (middle of edge)
         mx#=(x1#+x2#)/2
         my#=(y1#+y2#)/2

         // Calc normal from shape center
         dist#=getdistance2d(0,0,mx#,my#)
         if Dist#>0
            nx#=mx#/dist#         
            ny#=my#/dist#         
         else
            nx#=0
            ny#=0
         endif

         // dist from mid point to one edge of fragment..          
         Edges(Index).EdgeLength#=getdistance2d(mx#,my#,x2#,y2#)

         // Speed fragment is moving  (speed by the normal (direction) shape is facing)
         Edges(Index).speedX#=nx#*Speed#
         Edges(Index).speedY#=ny#*Speed#

         // mid point of line fragment
         Edges(Index).Xpos#=Xpos#+mx#
         Edges(Index).Ypos#=Ypos#+my#

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