[2005] draw a line

[champ0342]

The following is the code that executes on the click of button1. My problem is that my line is not drawing correctly. I have tested the output of the values that points the line in the correct direction. They are coming out correct. However, when the line draws, at an angle the angle is going in the wrong direction.

i.e. a 45 degree angle is drawing at an angle of 305

Any help is greatly appreciated.

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim ofd As New OpenFileDialog()

        Dim MyValue() As String

        x1 = 300
        y1 = 300

        ofd.InitialDirectory = "c:\"
        ofd.Filter = "txt files (*.txt)|*.txt|All files (*.*)|*.*"

        If ofd.ShowDialog() = System.Windows.Forms.DialogResult.OK Then
            Using sr As New System.IO.StreamReader(ofd.FileName)
                Do
                    MyValue = sr.ReadLine.Split
                    Dim myPen As New System.Drawing.Pen(System.Drawing.Color.Red)
                    Dim formGraphics As System.Drawing.Graphics
                    formGraphics = Me.CreateGraphics()
                    length = Convert.ToDouble(MyValue(0))
                    angle = Convert.ToDouble(MyValue(1))
                    y = angle * (Math.PI / 180)
                    x2 = x1 + length
                    y2 = y1 + ((length) * (Math.Sin(y)))
                    tmr.Enabled = True

                    formGraphics.DrawLine(myPen, Convert.ToInt32(x1), Convert.ToInt32(y1), Convert.ToInt32(x2), Convert.ToInt32(y2))
                    TextBoxX.Text = Convert.ToString(y1)
                    TextBoxY.Text = Convert.ToString(y2)
                    TextBoxAngle.Text = MyValue(1)
                    x1 = x2
                    y1 = y2
                    If sr.EndOfStream Then
                        tmr.Enabled = False
                    End If
                    Try
                    Catch Ex As Exception
                        MessageBox.Show("Cannot read file from disk. Click okay to try another file.")
                    End Try
                Loop Until sr.EndOfStream
            End Using
        End If
    End Sub

[Icyculyr]

What values are in MyValue(0) and MyValue(1)?

[champ0342]

the numbers vary. the first numbers is the distance of a line. the second number is the angle at which the line is to be drawn.

I have it working so that angles between 0 and 360 work. However anything above and below that does not work.

i.e.

10 -45

[jmcilhinney]

I haven't looked at your code but remember this. Traditionally the positive x axis is to the right and the positive y axis is upwards. On a WinForms control the positive y axis is downwards.

[michaelrawi]

jim, X axis always to the right, Y axis is downwards in winform.

@champ0342: You should draw the line on Paint event, rather than click, because it won't draw again when you minimize or move the form.. And graphic objects consume memory a lot if you can't manage them..

[champ0342]

how would i tell the program to clear anything drawn on this form?

[Lord Orwell]

isn't there an overloads for the linedraw that takes an angle as a parameter?

[jmcilhinney]

jim, X axis always to the right, Y axis is downwards in winform.

@champ0342: You should draw the line on Paint event, rather than click, because it won't draw again when you minimize or move the form.. And graphic objects consume memory a lot if you can't manage them..

Oops! That was a typo. I did mean the +ve y axis was down and I've edited my post.

Follow the Drawing link in my signature to see how to draw and "erase" lines on a control.