iOS Question How to draw a 30 degree line

[rfresh]

I know how to draw lines. What I need to do is draw a line at a specific angle, such as 30 degrees.

I don't know how to calculate the line angle for the given points of x1, y1, x2, y2?

Thanks...

 

[klaus]

You need to ne more precise on what exactly you want to draw.
x1 and y1 are the coordinates of the beginning point.
Then what limits the end point?
- an x coordinate ? then y2 = y1 + (x2 - x1) * CosD(30)
- a y coordinate ? then x2 = x1 + (y2 - y1) * SinD(30)
- the length of the line ? then
x2 = x1 + Length * CosD(30)
Y2 = y1 + Length * SinD(30)

 

[ilan]

here is a b4j code example:

#Region Project Attributes
    #MainFormWidth: 600
    #MainFormHeight: 600
#End Region

Sub Process_Globals
    Type point(x As Float, y As Float)
    Private fx As JFX
    Private MainForm As Form
    Private cnv As B4XCanvas
    Private xui As XUI
End Sub

Sub AppStart (Form1 As Form, Args() As String)
    MainForm = Form1
    'MainForm.RootPane.LoadLayout("Layout1") 'Load the layout file.
    MainForm.Show
    Dim center As point
    center.Initialize
    center.x = MainForm.RootPane.Width/2
    center.y = MainForm.RootPane.Height/2
  
    Dim lineLength As Int = 200
  
    cnv.Initialize(MainForm.RootPane)
  
    circleMekuvkav(center,lineLength/2)
  
    cnv.DrawLine(center.x,center.y,center.x+lineLength,center.y,xui.Color_Black,2) '0 deg line
    cnv.DrawLine(center.x,center.y,center.x+(lineLength*CosD(-30)),center.y+(lineLength*SinD(-30)),xui.Color_Black,2) '30 deg
End Sub

Sub circleMekuvkav(p As point,r As Int)
    cnv.DrawCircle(p.x,p.y,r,xui.Color_Red,False,1)
    For i = 0 To 360 Step 5
        cnv.DrawLine(p.x,p.y,p.x*((r*2)*CosD(i)),p.y*((r*2)*SinD(i)),xui.Color_White,5)
    Next
End Sub

'Return true to allow the default exceptions handler to handle the uncaught exception.
Sub Application_Error (Error As Exception, StackTrace As String) As Boolean
    Return True
End Sub

 

[rfresh]

Thank you Ilan...