Code archives/Graphics/Fast Circle

This code has been declared by its author to be Public Domain code.

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Fast Circle by Grey Alien
(Posted 21 years ago)
Uses Shagwana's cool circle algo but is 200 times faster due to WritePixelFast, so is able to be used realtime. Careful not to draw outside of the screen though or it'll crash. 
Function PlotFastCircle(xpos,ypos,radius) ;JB modification 28/08/05
  ;originally by Shagwana 2002-09-16 
  x=0 
  y=radius
  h=1-radius  
  c=255
  LockBuffer(BackBuffer)
  WritePixelFast(xpos+x,ypos+y,c)  ;Draw the starting pixels
  WritePixelFast(xpos-x,ypos-y,c)
  WritePixelFast(xpos+x,ypos-y,c)
  WritePixelFast(xpos-x,ypos+y,c)
  WritePixelFast(xpos+y,ypos+x,c)
  WritePixelFast(xpos-y,ypos-x,c)
  WritePixelFast(xpos+y,ypos-x,c)
  WritePixelFast(xpos-y,ypos+x,c)
  While y>x            ;Loop the arc
   If h<0
     h=h+(2*(x+1))
     x=x+1
     Else
     h=h+(2*(x-y))+5
     x=x+1
     y=y-1
     EndIf  
    WritePixelFast(xpos+x,ypos+y,c) ;Draw 1/8 at a time 
    WritePixelFast(xpos+y,ypos+x,c)
    WritePixelFast(xpos-x,ypos-y,c)
    WritePixelFast(xpos-y,ypos-x,c)
    WritePixelFast(xpos-x,ypos+y,c)
    WritePixelFast(xpos-y,ypos+x,c)
    WritePixelFast(xpos+x,ypos-y,c)
    WritePixelFast(xpos+y,ypos-x,c)
    Wend
  UnlockBuffer(BackBuffer)
End Function