[2008] Resolved - Drawing spirals using the Graphics object ?

[illskills]

I have been trying now for 2 nights to draw spirals in vb.net and its starting to get to me now :0(

Here's a link to the formula ...

http://www.mathematische-basteleien.de/spiral.htm

here's what i was trying todo ...

the code below is just drawing points which i was later going to edit to connect from point to point as soon as i got the spiral function working.

    Function Draw()
        Dim iImageCenterPointH As Integer = pbOut.Height / 2
        Dim iImageCenterPointW As Integer = pbOut.Width / 2
        Dim iCircleSpace As Integer = 10
        '# x²+y² = R² or [y = sqr(R²-x²) und y = -sqr(R²-x²)]

        Dim oGrapics As System.Drawing.Graphics
        Dim myImage As New Bitmap(pbOut.Width, pbOut.Height)
        pbOut.Image = myImage

        oGrapics = pbOut.CreateGraphics


        For i As Integer = 0 To 100 Step 5
            Dim x, y, r As Integer

            '# step 1 >>
            x = i
            y = 0
            r = (y * y) + (x * x)
            r = Math.Sqrt(r)
            myImage.SetPixel(iImageCenterPointW + r, iImageCenterPointH, Color.Black)

            '# step 2 >^
            x = i
            y = i
            r = (y * y) + (x * x)
            r = Math.Sqrt(r)
            myImage.SetPixel(iImageCenterPointW + (r / 2), iImageCenterPointH + (r / 2), Color.Black)

            '# step 3 ^^
            x = 0
            y = i
            r = (y * y) + (x * x)
            r = Math.Sqrt(r)
            myImage.SetPixel(iImageCenterPointW, iImageCenterPointH + r, Color.Black)

            '# step 4 ^^
            x = i
            y = -i
            r = (y * y) + (x * x)
            r = Math.Sqrt(r)
            myImage.SetPixel(iImageCenterPointW - (r / 2), iImageCenterPointH + (r / 2), Color.Black)

            x = -i
            y = i
            r = (y * y) + (x * x)
            r = Math.Sqrt(r)
            myImage.SetPixel(iImageCenterPointW + (r / 2), iImageCenterPointH - (r / 2), Color.Black)

            x = -i
            y = 0
            r = (y * y) + (x * x)
            r = Math.Sqrt(r)
            myImage.SetPixel(iImageCenterPointW - r, iImageCenterPointH, Color.Black)

            x = -i
            y = -i
            r = (y * y) + (x * x)
            r = Math.Sqrt(r)
            myImage.SetPixel(iImageCenterPointW - (r / 2), iImageCenterPointH - (r / 2), Color.Black)

            x = 0
            y = -i
            r = (y * y) + (x * x)
            r = Math.Sqrt(r)
            myImage.SetPixel(iImageCenterPointW, iImageCenterPointH - r, Color.Black)
        Next
        pbOut.Image = myImage
        Return ""
    End Function

im not 100% the output is matching the formula here's what im getting atm ...

[illskills]

would it make more sense going from the Rsqrd value rather than the x y cords?

[MaximilianMayrhofer]

Here is the code I use to draw a spiral on the form. You can specify the starting and ending angle. When drawing a spiral, think trigonometry. Imagine a pen moving along a ruler at a steady pace. The result would be a straight line, of course. But now spin the ruler from its end on the surface of the table, also at a steady rate. The result is a spiral. The depth between layers depends on the ratio between the straight line motion of the pen along the ruler, and the circular motion of the ruler itself:

Option Strict On
Option Explicit On

Public Class Form1
    Private Points As List(Of PointF)
    Private PenWidth As Int16

    Private Enum Direction
        Clockwise = -1
        AntiClockwise = 1
    End Enum

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Points = New List(Of PointF)
        PenWidth = 3

        Dim Center As PointF = New PointF(CSng(Me.Width / 2), CSng(Me.Height / 2))
        Dim Separation As Single = 10 + PenWidth
        Dim Turns As Integer = 8
        Dim Rotation As Direction = Direction.Clockwise
        Dim Displacement As Single = 20
        Dim StartAngle As Double = Math.PI / 4
        Dim EndAngle As Double

        StartAngle = Math.PI - StartAngle     'Orientate the angle relative to the 12'oclock position
        EndAngle = 2 * Turns * Math.PI + StartAngle

        If Rotation = Direction.Clockwise Then
            EndAngle = StartAngle
            StartAngle = 2 * Turns * Math.PI + EndAngle
        End If

        For Angle = StartAngle To EndAngle Step CInt(Rotation) * (Math.PI / 180)
            Points.Add(New PointF(CSng(Center.X + Displacement * Math.Sin(Angle)), CSng(Center.Y + Displacement * Math.Cos(Angle))))
            Displacement += Separation / 360
        Next
    End Sub

    Private Sub Form1_Paint(ByVal sender As System.Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles Me.Paint
        e.Graphics.DrawCurve(New Pen(Color.Black, PenWidth), Points.ToArray())
    End Sub
End Class

[illskills]

thanks bud was starting to get annoying writing my own function ;0)

ill check the code now n let you know how it goes ;0)

[illskills]

superb worked a treat ;0)
many thanks

[illskills]

thought you might want to check my modifications .... i whacked it into a function ....

if you want the code ill pm it to you ;0)

[MaximilianMayrhofer]

Yep I recognise the shape of my spirals It's alright, I put my code in a function a long time ago so that I could play around with spinning spirals.

[illskills]

im using it to design pieces of glass for my uni project i have waves / circles and now spirals working im using it to emulate me pouring pva glue onto glass for sand blasting later ... my little app can churn out more drawings in an hour than i could do in a year lol ;0)