Rotating a shape

[Ali Rizwan]

Hi all,
I have a big circle, and a small circle inside the big one.
Now I want to make a motion to small circle so that it will move with the boundary of the big circle inside or outside boundary.
How can I do this?
Thanks.

[debasisdas]

Use SIN and COS for the purpose.

[Killer42]

I have a big circle and a small circle inside the big one.
Now i want to make a motion to small circle so that it will moves with the boundry of the big circle inside or outside boundry.

So in fact, this question has nothing to do with rotating a shape - correct?

As for how, I'd say all you need to do is make sure that the Distance between the two centre-points plus the radius of the smaller circle doesn't exceed the radius of the larger one.

Pythagorus' theorem will give you the distance, and presumably you already know the radii, from drawing the circles.

Can you please explain in more detail what you mean by "move with the boundary of the big circle inside or outside boundary"? Also, what version of VB are you using?

[Peter Garrard]

This code will rotate a circle within a circle, and can be modified for rotation on the outside. Could be a start for a Spirograph program.

Sub Demo()
    Const Pi = 3.1415
    Dim radius1    As Long, radius2    As Long
    Dim Alpha      As Single, dAlpha     As Single
    Dim X1         As Single, X2         As Single
    Dim X3         As Single, Y1         As Single
    Dim Y2         As Single, Y3         As Single
    Dim cx         As Single, cy         As Single
    Dim i          As Integer, j          As Integer
    Dim z          As Long, offset        As Integer
    Dim k          As Integer, num        As Integer
    BackColor = vbWhite
    AutoRedraw = True
    Cls
    radius1 = ScaleHeight / 2 - 100
    radius2 = 1600
 
    ' find center screen and Draw the circle.
    ForeColor = vbRed
    cx = (ScaleWidth) / 2
    cy = (ScaleHeight) / 2
    Circle (cx, cy), radius1
    ForeColor = vbBlack
 
    dAlpha = Pi / 10     'test value for 20 lines
 
    Alpha = 0
    For i = 1 To 21
        'Draw radiating lines.
        X1 = cx + (radius1) * Cos(Alpha)
        Y1 = cy + (radius1) * Sin(Alpha)
        'Line (cx, cy)-(X1, Y1)
 
        'determine new position where smaller circles will be drawn
        X3 = cx + ((radius1 - (radius2 + 20)) * Cos(Alpha))
        Y3 = cy + ((radius1 - (radius2 + 20)) * Sin(Alpha))
 
        'draw dots on the lines showing center point for smaller circles
        DrawWidth = 4
        'PSet (X3, Y3)
        DrawWidth = 1
        'draw the smaller circle
        If radius2 > 0 Then
          Circle (X3, Y3), radius2
        End If
 
        'blank out the last line/circle drawn to creat rotating line/circle
        If i < 21 Then
          For z = 1 To 5000000: Next
          DoEvents
          ForeColor = vbWhite
          Circle (X3, Y3), radius2
          Line (cx, cy)-(X1, Y1)
        End If
        ForeColor = vbBlack
        'draw dots on the outer circle
        DrawWidth = 4
        'PSet (X2, Y2)
        DrawWidth = 1
        Alpha = Alpha + dAlpha
    Next i
 
End Sub

[Killer42]

This code will rotate a circle within a circle...

I think we have a terminology problem here. If you rotate a circle, surely this has no effect.

Ali, can you give us some feedback here, on what you actually wanted to do, and how it's going?