Moving an object between two points

[kevin]

This  mini tutorial, well example source, shows one a way how you can move an object between two known points.

The demo lets the user select the start & end point with the mouse, then moves the object (a circle in this case) between these.   When complete, the demo lets you repeat this process over and over.

PlayBASIC Code: [Select]

  Speed#=2

; init the variables used 
  gosub Reset_Variables
  
  
; start of main loop
  Do

; clear the screen 
  cls 0  


  
;Draw the start and end points (which default to be being off screen)
  
     Circlec StartPoint_X,StartPoint_Y,5,0,rgb(255,0,255)
     Circlec EndPoint_X,EndPoint_Y,5,0,rgb(155,255,055)

; Draw the MOve Objects position 
     Circlec CurrentPoint_X#,CurrentPoint_Y#,5,1,rgb(255,255,255)

   
; Select what mode the demo is in.
  select MoveMent_Mode


; -----------------------------------------------------
; mode0 = select Starting point of objects path  
; -----------------------------------------------------
     case 0
    Print "Select Start point"   
    While MouseButton()=1
        StartPoint_X=MouseX()
      StartPoint_Y=MouseY()
      FlushMouse
      inc MoveMent_Mode
    endwhile

; -----------------------------------------------------
; mode1 = select strart point   and calc movement vectors
; -----------------------------------------------------
     case 1   
    Print "Select End point"   
  
    While MouseButton()=1
       EndPoint_X=MouseX()
       EndPoint_Y=MouseY()
      FlushMouse
      inc MoveMent_Mode

   ; calc the X & Y steps
       Dist#=getdistance2d(StartPoint_X,StartPoint_Y,EndPoint_X,EndPointY)

   ; Calc the time it'll take to move this distance at this speed
   ; ie. the number of steps
       Movement_Time=Dist#/speed# 
      
   ; calc movement vector (change in X & Y over this time peroid)
       Movement_StepX#=(EndPOint_X-StartPoint_X)/Float(Movement_Time)
       Movement_StepY#=(EndPOint_Y-StartPoint_Y)/Float(Movement_Time)

   ; Init the current Positions X& Y to the starting position
       CurrentPoint_X#=StartPoint_X
       CurrentPoint_Y#=StartPoint_Y
    endwhile


; -----------------------------------------------------
; mode2 = Move the object between the two points  
; -----------------------------------------------------
     case 2
    print "Moving Object"
  
   ; Calc the time it'll take
       
       dec Movement_Time
       if Movement_time<0
         
    ; On the last move, force the End point as the current position
        CurrentPoint_X#=EndPoint_X
        CurrentPoint_Y#=EndPoint_Y   
         inc MoveMent_Mode

       else
         ; Init the current POsition from the starting position
         CurrentPoint_X#=CurrentPoint_X#+MoveMent_StepX#
         CurrentPoint_Y#=CurrentPoint_Y#+MoveMent_StepY#
       endif  
  


; -----------------------------------------------------
     case 3
; -----------------------------------------------------
       print "DONE - Press mouse to restart"
       
       While MouseButton()=1
        StartPoint_X=MouseX()
        StartPoint_Y=MouseY()
      FlushMouse
      gosub Reset_Variables
       endwhile
      
  endselect
   
   

  Sync
  loop



Reset_Variables:

; INit the Mode variable to zero.  This varibale is used
; select what mode the demo is in.  I.e. it's accepting input
; from the user, or moving the ball object
  MoveMent_Mode=0

; Set the Time Varibale. This Holds the number of frames
; it'll take for our object to move between the two points
  MoveMent_Time=-1


; CurretPOint X & Y are used as the moving objects current position
  CurrentPOint_X#=-10
  CurrentPOint_Y#=0

; StartPoint X& Y are used to record the objects starting position
  StartPOint_X=-10
  StartPOint_Y=0

; EndPoint X& Y are used to record the objects end position
  EndPoint_X=-0
  EndPoint_Y=0

; Movement Step X +Y hold the change in objects Move along the X and Y axis   
  Movement_StepX#=0
  Movement_StepY#=0

 return






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