iOS Question How to draw a 30 degree line

rfresh

Well-Known Member
Licensed User
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

Expert
Licensed User
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

Expert
Licensed User
here is a b4j code example:

B4X:
#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
30deg.png
 

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