Bezier curves

[empty]

This example shows how to do Bezier curves in PlayBasic.

PlayBASIC Code: [Select]

Constant Smoothness# = 0.05 // the smaller the value the smoother the curve

Type TPoint
   x,y
EndType

Dim Points(4) As TPoint

Do
   Cls 0
   Print "Place 4 points with mouseclicks"
   Print "1st = Start point, 2nd = Control Point 1, 3rd = Control Point 2, 4th = End point"
   Ink $00FF00
   count = 0
   Repeat
      Text 1,10," "
      If MouseButton() = 1
         Inc count 
         BoxC MouseX()-2, MouseY()-2, MouseX()+2, MouseY()+2, 1, 255
         Points(Count).X = MouseX()
         Points(Count).Y = MouseY()
         While MouseButton() = 1
            Text 1, 1," "
            Sync
         EndWhile
      EndIf
      Sync
   Until count=4
   
   old_x = Points(1).x
   old_y = Points(1).y
   For t# = 0.0 To 1.0 Step Smoothness#
      f1# = (1-t#)*(1-t#)*(1-t#)
      f2# = 3*t#*(1-t#)*(1-t#)
      f3# = 3*t#*t#*(1-t#)
      f4# = t#*t#*t#
      new_x = f1#*Points(1).x + f2#*Points(2).x + f3#*Points(3).x + f4#*Points(4).x
      new_y = f1#*Points(1).y + f2#*Points(2).y + f3#*Points(3).y + f4#*Points(4).y
      Line old_x, old_y, new_x, new_y
      old_x = new_x
      old_y = new_y
   Next t#
   Line old_x, old_y, Points(4).x, Points(4).y   
   Sync 
   Ink $FFFFFF
   Print "Press a key"
   Sync 
   WaitKey
Loop

 This version is for older version of PlayBasic V1.63 such as learning edition (and older retail editions)

PlayBASIC Code: [Select]

constant Smoothness = 0.05*100 // the smaller the value the smoother the curve

Type TPoint
   x,y
EndType

Dim Points(4) As TPoint

Do
   Cls 0
   Print "Place 4 points with mouseclicks"
   Print "1st = Start point, 2nd = Control Point 1, 3rd = Control Point 2, 4th = End point"
   Ink $00FF00
   count = 0
   Repeat
      Text 1,10," "
      If MouseButton() = 1
         Inc count 
         BoxC MouseX()-2, MouseY()-2, MouseX()+2, MouseY()+2, 1, 255
         Points(Count).X = MouseX()
         Points(Count).Y = MouseY()
         While MouseButton() = 1
            Text 1, 1," "
            Sync
         EndWhile
      EndIf
      Sync
   Until count=4
   
   old_x = Points(1).x
   old_y = Points(1).y
   For tlp = 0 To 100 Step Smoothness
      t#=tlp/100.0
   
      
      f1# = (1-t#)*(1-t#)*(1-t#)
      f2# = 3*t#*(1-t#)*(1-t#)
      f3# = 3*t#*t#*(1-t#)
      f4# = t#*t#*t#
      new_x = f1#*Points(1).x + f2#*Points(2).x + f3#*Points(3).x + f4#*Points(4).x
      new_y = f1#*Points(1).y + f2#*Points(2).y + f3#*Points(3).y + f4#*Points(4).y
      Line old_x, old_y, new_x, new_y
      old_x = new_x
      old_y = new_y
   Next 
   Line old_x, old_y, Points(4).x, Points(4).y   
   Sync 
   Ink $FFFFFF
   Print "Press a key"
   Sync 
   WaitKey
Loop

[monkeybot]

all i get is a straight line
???

[kevin]

Looks like a curve to me

[monkeybot]

it works with compiler 1.64j and IDE 1.1.7
but not with compiler 1.64m and IDE 1.15f
i can only run the earlier version as the IDE crashes too much.

[kevin]

 The example uses a float step in For a loop,  this can cause  issues with some editions of  PB ( from about 1.63 through -> 1.64i) due to some runtime opt's.   So above, i've posted a version that will run in old clunkers. 

[monkeybot]

i would like to be upto date but can't,i am going to re-install xp soon will see if that helps with the crashing.