Module to move object from A to B

blindwig · #1 07-02-2003, 10:36 PM

OK, I keep seeing posts here from people asking how to move an object (like a picture or image) around on a form. I've made a little module to use for moving an object toward a destination, not directly to that destination, so that you can loop and move the object as fast or slow as you want.

Here's the module source:

Code:

Option Explicit

'gotta have some pi!
Global Const pi = 3.14159265

'Picks a spot that allows object to be fully visable in it's parent,
'assuming that the object is smaller than it's parent
Public Sub PickASpot(ByRef objTarget As Object, _
   ByRef TargetX, ByRef TargetY)
    objTarget.Parent.ScaleMode = 1
    TargetX = Int(Rnd * (objTarget.Parent.ScaleWidth - objTarget.Width))
    TargetY = Int(Rnd * (objTarget.Parent.ScaleHeight - objTarget.Height))
End Sub

'Returns the distance between 2 points
Private Function Distance(ByVal x1 As Long, ByVal y1 As Long, _
   ByVal x2 As Long, ByVal y2 As Long) As Double
    Distance = Sqr((x2 - x1) ^ 2 + (y2 - y1) ^ 2)
End Function

'Will move an object toward a target location, only as far as MaxMovement
Public Function SlideObjTo(ByRef objTarget As Object, _
   ByVal TargetX As Long, ByVal TargetY As Long, _
   Optional ByVal MaxMovement As Long = -1) As Boolean
    Dim CurX, CurY As Long
    CurX = objTarget.Left
    CurY = objTarget.Top
    'Default MaxMovement is half the diagonal size of the object
    If MaxMovement <= 0 Then MaxMovement = Sqr((objTarget.Height) _
       ^ 2 + (objTarget.Width) ^ 2) / 2
    If Distance(CurX, CurY, TargetX, TargetY) > MaxMovement Then
        MoveObjTowards objTarget, TargetX, TargetY, MaxMovement
    Else
        MoveObjTo objTarget, TargetX, TargetY
    End If
    'Return tells you if the object has reached it's destination
    SlideObjTo = (Abs(objTarget.Left - TargetX) <= Screen.TwipsPerPixelX) _
       And (Abs(objTarget.Top - TargetY) <= Screen.TwipsPerPixelY)
End Function

'Will move an object directly to the target location
Private Sub MoveObjTo(ByRef objTarget As Object, _
   ByVal TargetX As Long, ByVal TargetY As Long)
    objTarget.Left = TargetX
    objTarget.Top = TargetY
End Sub

'Will move an object toward a target location as far as DISTANCE
Private Sub MoveObjTowards(ByRef objTarget As Object, _
ByVal TargetX As Long, ByVal TargetY As Long, ByVal Distance As Long)
    Dim Angle As Double
    Dim X, Y As Long
    X = objTarget.Left - TargetX
    Y = objTarget.Top - TargetY
    If X > 0 Then
        Angle = Atn(Y / X) + pi
    ElseIf X = 0 Then
        If Y < 0 Then Angle = pi / 2 Else Angle = -pi / 2
    ElseIf X < 0 Then
        Angle = Atn(Y / X)
    End If
    X = Int(Cos(Angle) * Distance)
    Y = Int(Sin(Angle) * Distance)
    objTarget.Left = objTarget.Left + X
    objTarget.Top = objTarget.Top + Y
End Sub

and here is a form you can use to demo the module. It has an image and a timer:

Code:

Dim DestX As Long, DestY As Long

Private Sub Form_Load()
    PickASpot Image1, DestX, DestY
End Sub

Private Sub Timer1_Timer()
    If SlideObjTo(Image1, DestX, DestY) Then PickASpot Image1, DestX, DestY
    Me.Caption = "Moving from (" & Image1.Left & "," & Image1.Top & _
       ") to (" & DestX & "," & DestY & ")"
End Sub

As always, comments are welcome!

blindwig · #2 07-06-2003, 12:17 PM

OK, I just added another function to my module, to be used when you don't know the object's exact destination, and would rather move it by trajectory and velocity. Here's the code (goes in the module):

Code:

'Moves an object in the direction DEGREE by DISTANCE units
'Note that DEGREE is actual degrees (0-360), not radians (0-2pi)
'Note that 0 DEGREE is not straight up, but to the right, and goes clockwise from there
Public Sub MoveObjByTrajectory(ByRef objTarget As Object, ByVal Degree As Double, Optional ByVal Distance As Double = -1)
    Dim X, Y As Long
    'Default Distance is half the diagonal size of the object
    If Distance <= 0 Then Distance = Sqr((objTarget.Height) ^ 2 + (objTarget.Width) ^ 2) / 2
    X = Int(Cos(Degree * pi / 180) * Distance)
    Y = Int(Sin(Degree * pi / 180) * Distance)
    objTarget.Left = objTarget.Left + X
    objTarget.Top = objTarget.Top + Y
End Sub

And to use it, for example:

Code:

MoveObjByTrajectory Image1, rnd*360

Enjoiy!