🐢 B4XTurtle - Library for teachers and parents

Erel · Apr 22, 2020

B4XTurtle is a library inspired by classic Logo programming language and TKP project: http://teachingkidsprogramming.org/
It is a cross platform library.
The purpose of B4XTurtle is to help with teaching programming. Drawing with the turtle is fun and it provides a simple visual feedback to the student.

Presentation about B4XTurtle:

You are welcome to try it and provide feedback.
Examples: https://www.b4x.com/android/forum/threads/-b4xturtle-examples-for-teachers-and-parents.116979/

Updates:

v1.06 - New StartPolygon and FillPolygon methods - better alternative, in most cases, to the Fill method.
v1.05 - Fixes an issue where the turtle could disappear when moving outside of the visible area, instead of appearing on the other side.
v1.04 - Fixes an issue with Fill which can cause the program to hang.
v1.03 - Multiple layers, DrawBitmap and other improvements.
v1.02 - Fill, Arc and RandomColor
v1.01 - RabbitMode and other improvements.

B4XTurtle is an internal library.

Erel · Apr 22, 2020

Who can draw this star:

?

walterf25 · Apr 22, 2020

Erel said:
Who can draw this star:

?

Multiple Star:

    For i = 1 To 5
        canvas.SetPenColor(Rnd(xui.Color_Black, xui.Color_White))
        For j = 1 To 5
            canvas.SetPenColor(Rnd(xui.Color_Black, xui.Color_White))
            canvas.MoveForward(30).TurnLeft(144)
        Next
        canvas.MoveForward(100).TurnLeft(144)
    Next

Easy

Erel · Apr 23, 2020

More elegant

B4X:

 DrawStar(200)

Sub DrawStar (Size As Int)
    If Size < 50 Then Return
    For i = 1 To 5
        Turtle.SetPenColor(Rnd(xui.Color_Black, xui.Color_White))
        Turtle.MoveForward(Size).TurnLeft(144)
        DrawStar(Size / 4)
    Next
End Sub

ilan · Apr 23, 2020

hi,

i have a question please. when i start the program the turtle starts immediately to run.
but in appstart event (b4j) there is no command for that.

B4X:

Sub AppStart (Form1 As Form, Args() As String)
    MainForm = Form1
    MainForm.RootPane.LoadLayout("Main")
    MainForm.Show
End Sub

so it means that when the custom view is added it calles immediately the turtle_start event. is it possible to control that?

thanx

barx · Apr 23, 2020

ilan said:
hi,

i have a question please. when i start the program the turtle starts immediately to run.
but in appstart event (b4j) there is no command for that.

B4X:

Sub AppStart (Form1 As Form, Args() As String) MainForm = Form1 MainForm.RootPane.LoadLayout("Main") MainForm.Show End Sub

so it means that when the custom view is added it calles immediately the turtle_start event. is it possible to control that?

thanx

I don't think Turtles can 'run'. I've never seen one run anyway

ilan · Apr 23, 2020

actually this lib has a lot potential. i would like to just get positions from the turtle and draw what ever i want like a sprite in a loop.
i will opwn the bas file and see how i can edit it.

like in this event:

B4X:

    If State.PenDown Then
        MainLayer.DrawLine(UserToCanvas(State.UserX), UserToCanvas(State.UserY), UserToCanvas(X), UserToCanvas(Y), State.PenColor, UserToCanvas(State.PenThickness))
    End If

instead of drawing a line i can draw a sprite in a loop.

will check it later when i have more time

thanx, erel

EDIT: and also the DrawTurtle event can be used to draw the animated sprite.

amidgeha · Apr 23, 2020

Programmers of all ages and students can use this library to implement the L-system or Lindenmayer system

Erel · Apr 23, 2020

ilan said:
so it means that when the custom view is added it calles immediately the turtle_start event. is it possible to control that?

Nothing special. Just raises an event with CallSub.

barx said:
I don't think Turtles can 'run'. I've never seen one run anyway

It will soon have a rabbit mode...

There is a use case for this which needs some explanation.

rabbitBUSH · Apr 23, 2020

Erel said:
It will soon have a rabbit mode...

YES YES YES YES .... recognition! Lets go around the bush again,

Erel · Apr 26, 2020

Library reference: https://www.b4x.com/android/forum/threads/-b4xturtle-reference.116893/

Updates:

v1.01 - RabbitMode and other improvements.

Erel · Apr 27, 2020

Another quiz:

This code draws a circle:

B4X:

Sub Circle
For i = 1 to 360
 Turtle.MoveForward(1).TurnRight(1)
Next
End Sub

How do we draw a circle with radius = r ?

B4X:

Sub Circle (r As Float)
 For i = 1 to 360
 '??????????
Next
End Sub

LucaMs · Apr 27, 2020

Erel said:
How do we draw a circle with radius = r ?

LucaMs · Apr 27, 2020

Erel · Apr 27, 2020

Can you draw this ?

The length of each line is obviously 2 * r.

LucaMs · Apr 27, 2020

Sure!

LucaMs · Apr 27, 2020

Funny; I feel like a kid (almost 60 years old . No, only 59.54 y.o. )

LucaMs · Apr 27, 2020

barx said:
I don't think Turtles can 'run'. I've never seen one run anyway

Everything is relative:
_ _ _

--> "Look how far that exhibitionist runs"

Erel · Apr 28, 2020

Nice Luca! Post the code.

ilan · Apr 28, 2020

if the code does not need to be in the for...next loop then it could be done like this:

B4X:

Sub Circle (r As Float)
    For i = 1 To 360
        Turtle.MoveForward(((r*2)*cPI)/360).TurnLeft(1)
    Next
    Turtle.TurnLeft(90).MoveForward(r*2)
    Turtle.PenUp.TurnLeft(180).MoveForward(r)
    Turtle.PenDown.TurnLeft(90).MoveForward(r)
    Turtle.PenUp.TurnLeft(180).MoveForward(r)
    Turtle.PenDown.MoveForward(r)
End Sub

i am sure there is a better and shorter way

🐢 B4XTurtle - Library for teachers and parents

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