Motion Blur

[kevin]

 Motion Blur Via Alpha Channel

   There's any number of the approaches to doing motion blur.  The most common and the stable diet of perhaps a decade or more worth demos, and those modern bullet hell styled shoot'em'ups, is achieved by simply dimming the frame buffer and drawing over it.   So you take the old image, dim it a little or a lot (for the amount of the blur), then draw over it again.  That's it.   You can do the same thing for individual sprites etc.  

   In this demo we're drawing a windmill styled shape on a temp cache, this buffer is then dimmed, rather cleared between frames and then drawn to the scene.  The result is that you see, it's current position plus past positions blurred together.

  This one was written in PB1.64, it might have to be modified for use with 1.63 or older.

PlayBASIC Code: [Select]

   setfps 60
   openscreen 800,600,32,2
   windmillsize=200
    img=newimage(windmillsize,windmillsize)
   prepareafximage img
   
   
   cog=Create_Cog_Shape(windmillsize/2,windmillsize/2*0.2,15)


   Alpha=128
   speed#=2.5
   
   Do
      ; draw a backdrop
      c1=rgb(60,110,30)
      c2=rgb(200,70,10)
      shadebox 0,0,800,600,c1,c1,c2,c2

      ; depreciate alpha of buffer
       rendertoimage img
      inkmode 1+2048
      boxc 0,0,1000,1000,true,argb(Alpha,155,155,155)
      inkmode 1

      ; refresh buffer foreground
      rotateshape cog,angle#,1
      ink argb(255,255,155,055)
      drawshape cog,windmillsize/2,windmillsize/2,2
      angle#=wrapangle(Angle#,-speed#)

      ; renderscene
      rendertoscreen      
      x1=400
      y1=300
      line x1,y1,200,800
      line x1,y1,600,800
      drawimage img,x1-(windmillsize/2),y1-(windmillsize/2),true

      ; control speed an 'blur length' 
      if upkey() then    Alpha=ClipRange(Alpha+2,2,256)
      if downkey() then    Alpha=ClipRange(Alpha-2,2,256)
      if leftkey() then Speed#=Speed#+0.05
      if rightkey() then Speed#=Speed#-0.05

      text 0,0,alpha
      text 0,20,speed#

      sync 
   Loop
   
   

Function Create_Cog_Shape(outterRadius,InnerRadius,sides)
   sides=sides -(mod(sides,2))   
   EdgeCount   =Sides*2
   VertexCount   =Sides*2
   ThisShape   =NewShape(VertexCount+1,EdgeCount+1)

   For lp=0 to sides
      x#=Cosradius(angle#,OutterRadius)
      y#=Sinradius(angle#,OutterRadius)
      SetshapeVertex thisshape,Numberofvertex,x#,y#
      inc Numberofvertex
      x#=Cosradius(angle#,InnerRadius)
      y#=Sinradius(angle#,InnerRadius)
      SetshapeVertex Thisshape,Numberofvertex,x#,y#
      inc Numberofvertex
      angle#=angle#+(360.0/Sides)
   next


   For Vertex=0 to Numberofvertex-2 step 2
      NextVertex=vertex+1
      if NextVertex=>Numberofvertex then nextVertex=Numberofvertex-NextVertex
      SetshapeEdge Thisshape,Edge,vertex,Nextvertex
      inc edge

      if Outline
         SrcVertex=Vertex
         NextVertex2=vertex+2
         if NextVertex2=>Numberofvertex then nextVertex2=Numberofvertex-NextVertex
      else
         SrcVertex=NextVertex
         NextVertex2=vertex+3
         if NextVertex2=>Numberofvertex then nextVertex2=Numberofvertex-NextVertex
      endif

      SetshapeEdge Thisshape,Edge,Srcvertex,Nextvertex2
      inc edge

      Outline=1-Outline
   next
   
EndFunction ThisShape

[ATLUS]

its not blur image does not run

[thaaks]

Works fine here on my machine.

ATLUS, try cursor up and down keys to modify the blur factor, use cursor left and right to change rotation speed.

@BlinkOk: See, it does work in real time   ;) You just need to know how. Correction: You just need to know a guy who knows how  ;D

Thanks to Kevin for this wonderful example and teaching lesson!

[ATLUS]

Works fine here on my machine.

ATLUS, try cursor up and down keys to modify the blur factor, use cursor left and right to change rotation speed.

@BlinkOk: See, it does work in real time   ;) You just need to know how. Correction: You just need to know a guy who knows how  ;D

Thanks to Kevin for this wonderful example and teaching lesson!

i see code and try click arows keys. Its not monitor blur.