spiral draw change

Howdy, Y'all...

The below code draws a spiral...code shows that there are 4 textboxes asking for information for the user to vary the spiral, and a "go" button. It seems to work fine.

However, I want the spiral to go from "out" to "in" rather than the way it is being drawn now ("in" to "out").

What is the best way to accomplish this Is a different formula in order, or can I store the points in some slick temporary fashion to be fed back into to the graphics paint in reverse order

I don't expect you to do it for me...just help me point the way to the alternatives...

Thanks,

Nightowly

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Imports system.drawing

Imports system.drawing.drawing2D

Public Class Form1

Public Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

'size Form1

Dim workingRectangle As System.Drawing.Rectangle = Screen.PrimaryScreen.WorkingArea

Me.MaximumSize = New System.Drawing.Size(workingRectangle.Width - 15, workingRectangle.Height - 15)

'locate Form1

Me.Location = New System.Drawing.Point(5, 5)

End Sub

Public Sub Form1_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles Me.Paint

End Sub

Public Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

Dim skyBluePen As New Pen(Brushes.DeepSkyBlue)

skyBluePen.Width = 2.0F

Dim a As Double = 0.1

Dim b As Double = 0.1

Dim ang As Double = 360

Dim i As Integer = 0

Dim iMax As Integer = 50

Dim spiralLine As Graphics = Me.CreateGraphics

If TextBox1.Text = "" Then

MessageBox.Show("Please enter a numeral between 0 and 1")

Else

a = CDbl(TextBox1.Text)

End If

If TextBox2.Text = "" Then

MessageBox.Show("Please enter a numeral between 0 and 1")

Else

b = CDbl(TextBox2.Text)

End If

If TextBox3.Text = "" Then

MessageBox.Show("Please enter a numeral between 0 and 1800")

Else

ang = CDbl(TextBox3.Text)

End If

If TextBox4.Text = "" Then

MessageBox.Show("Please enter a numeral between 0 and 25000")

Else

iMax = CInt(TextBox4.Text)

End If

Dim cX, X1, X2 As Double

Dim cY, Y1, Y2 As Double

'get the center of the form to start the spiral there

cX = CLng(Me.ClientRectangle.Width / 2)

cY = CLng(Me.ClientRectangle.Height / 2)

'loop round to plot the points of the spiral.

For i = 0 To iMax

ang = (Math.PI / 720) * i

If X1 = 0 And Y1 = 0 Then

X1 = cX + ((a * Math.Cos(ang)) * Math.Exp(b * ang))

Y1 = cY - ((a * Math.Sin(ang)) * Math.Exp(b * ang))

i += 1

X2 = cX + ((a * Math.Cos(ang)) * Math.Exp(b * ang))

Y2 = cY - ((a * Math.Sin(ang)) * Math.Exp(b * ang))

Else

X1 = X2 'X4

Y1 = Y2 'Y4

X2 = cX + ((a * Math.Cos(ang)) * Math.Exp(b * ang))

Y2 = cY - ((a * Math.Sin(ang)) * Math.Exp(b * ang))

Dim Spt1 As New Point(CInt(X1), CInt(Y1))

Dim Spt2 As New Point(CInt(X2), CInt(Y2))

spiralLine.DrawLine(skyBluePen, CInt(X1), CInt(Y1), CInt(X2), CInt(Y2))

End If

Next i

End Sub

End Class