Activities/Turtle Art/Plugins

Plugins

As of Version 106, there is plugin support for Turtle Art. The basic idea is to let developers add new palettes and blocks to support additional functionality without having to make changes to any of the core Turtle Art packages. If a plugin is present, it is loaded when Turtle Art is launched and any palettes or blocks defined by the plugin are made available to the user.

The plugin mechanism is currently used to provide support for sensors, the camera, RFID, and the Media, Extras, and Portfolio palettes. A plugin has been developed for WeDo and additional plugins are being developed for Arduino, NXT, and GoGo.

How to install a plugin

Plugins are typically distributed as a *.tar.gz archive

In Gnome, click on the link in your browser and open with Archive Manager, extract the files in the plugins directory of the archive to

/home/olpc/Activities/TurtleArt.activity/plugins

you may need to make the Activities directory writeable first, in Terminal type

chmod 777 /home/olpc/Activities

If your distribution does not include Gnome, the following commands in Terminal will download the Physics archive to the current directory

cd ~/Activities/TurtleArt.activity
wget http://wiki.sugarlabs.org/images/c/c1/Physics-plugin.tar.gz
gunzip Physics-plugin.tar.gz
tar xvf Physics-plugin.tar

Note that you should not need root access to install plugins into your home directory.

Available plugins

These plugins would typically already be installed

• turtleart-extras (the extra palettes that distinguish Turtle Blocks from Turtle Art)
• turtleart-camera
• turtleart-sensors
• rfid (This plugin allows interfacing with a RFID reader)

Project Butia

Add a palette to control the Butiá robot

Proyecto Butiá

Download: butia_plugin.tar.gz

FollowMe

This plugin uses the camera and get the position of an object of a color. The plugin add this palette:

Download: followme_ta_plugin.zip

Examples:

The "classic" use: on "Start", use the "Calibrate" block to open a window that shows the camera output. In the center of that window there is red square. The FollowMe Plugin uses an algorithm that obtains the "promedial" color of the object in the square. The result of that algorithm is shown in a small square in the corner. When you consider that the color is a good "representation of the object", press any key, the window will close, and FollowMe will use this color. After calibration, you can use the "X position" and "Y position" blocks. The block "X position" is the "center" of the object seen by the camera along the "X" (horizontal) axis. This value is an integer between 0 and 320. When the object is not detected,the algorithm returns -1. The operation of the "Y position" block are the same, but returns the position respect the "Y" (vertical) axis. The value returned is between 0 and 240.

When you know the color to "follow" (it occurs rarely, since the color varies under changing light conditions) you can use the "Follow RGB" block. This block sets the color directly to the algorithm. In all cases, the color has a threshold of 25 in each component set by default. In a future version, this threshold will be modifiable.

The third option, is to use the "FollowMe" block that "follows" a generic color similar to that shown.

Videos of the plugin ongoing:

FollowMe plugin in TurtleArt - Part 1

FollowMe plugin in TurtleArt - Part 2

The code used in this videos:

Currency

This plugin adds a pallette of currency (notes and coins), these items can be acted on by arithmetic operators

File:Oz-coins.tar.gz Australian coins plugin

File:Oz-bills.tar.gz Australian bills plugin

File:Oz-coins-and-bills.tar.gz Australian coins and bills plugin

File:Colombia-currency.tar.gz Colombian peso plugin

File:Mexican-currency.tar.gz Mexican peso plugin

File:Paraguay-currency.tar.gz Paraguay Gurani plugin

File:Rwanda-currency.tar.gz Rwanda francs plugin

File:UY-currency.tar.gz Uruguayan peso plugin

File:US-bills.tar.gz US bills plugin

File:US-currency.tar.gz US dollar plugin

Physics

This plugin allows you to construct a Physics model which can be saved to the Journal and run with the Physics Activity Activities/Physics

Use these blocks to create objects that are added to the bodylist and jointlist of a Box2d database used by the Physics Activity. Objects are positioned by the turtle x,y and colored based on the current pen attributes. From left to right:

• start polygon: use the current turtle x,y position to specify the first vertex of a polygon
• add point: use the current turtle x,y position to add a vertex to a polygon
• end polygon: use the current turtle x,y position to specify the last vertex of a polygon
• end filled polygon: use the current turtle x,y position to specify the last vertex of a filled polygon

Note: The polygon must be 'normal', e.g., no crossed lines; no holes. Since Box2d does not support concave polygons, all polygons are converted to triangles (triangulation). (In Turtle Blocks, these triangles are shown by slight variations in color.)

• triangle: add a triangle object at the current turtle x,y position
• circle: add a circle object at the current turtle x,y position
• rectangle: add a rectangle object at the current turtle x,y position
• gear: add a gear object at the current turtle x,y position with the number of teeth as the argument
• motor: add a motor at the current turtle x,y position (attached to the object at this position)
• pin: add a pin at the current turtle x,y position (attached to the object at this position)
• joint: add a joint between the object at the current turtle x,y position and the object at x, y
• density: set the object density (0 is light; 1 is heavy)
• friction: set the object friction (0 is slippery; 1 is sticky)
• bounciness: set the object restitution (0 is rigid; 1 is bouncy)
• save as Physics project: save the current bodylist and jointlist as a Physics project in the Journal

Note: The current model is cleared whenever the Erase button is pressed or a Clean block is run.

Where to get the Physics plugin

File:Physics-plugin.tar.gz Physics plugin

Example

A simple gear and motor generated in Turtle Art:

File:TAgear.ta File:Gear.physics

How to write a plugin

Your plugin should be placed in a subdirectory of the plugins directory. In that subdirectory, you need to create a .py file that defines a subclass of the Plugin class. The directory and .py file must have the same name and the subclass must also have the same name, with the additional requirement that the first letter of the class name be capitalized.

For example:

• the camera plugin, camera_sensor.py is in ./plugins/camera_sensor
• the class, Camera_sensor is defined in camera_sensor.py, e.g.,

from plugins.plugin import Plugin
class Camera_sensor(Plugin):

In that subdirectory, you will also need a __init__.py file (which can be empty) and optionally, an icon subdirectory for your palette icon.

Turtle Art calls the __init__ method when starting up and traps import errors as its means to determine whether or not a plugin has the resources it needs to run. (You may want to remove this exception handler when debugging your plugin. It is in the _init_plugins method in tawindow.py.) It then calls the setup method when creating the palettes. It calls the start method whenever a stack of blocks is run and the stop method when execution is over. Also, there are methods for goto_background, return_to_foreground, and quit. (These methods are typically ignored.)

Adding a new palette is simply a matter of:

   palette = make_palette('mypalette',  # the name of your palette
                          colors=["#00FF00", "#00A000"],
                          help_string=_('Palette of my custom commands'))

For example, if we want to add a new turtle command, 'uturn', we'd use the add_block method in the Palette class.

   palette.add_block('uturn',  # the name of your block
                     style='basic-style',  # the block style
                     label=_('u turn'),  # the label for the block
                     prim_name='uturn',  # code reference (see below)
                     help_string=_('turns the turtle 180 degrees'))

   # Next, you need to define what your block will do:
   # def_prim takes 3 arguments: the primitive name, the number of
   # of arguments, 0 in this case, and the function to call, in this
   # case, the canvas function to set the heading.
   self.tw.lc.def_prim('uturn', 0, lambda self: self.tw.canvas.seth(self.tw.canvas.heading + 180))

That's it. When you next run Turtle Art, you will have a 'uturn' block on the 'mypalette' palette.

You will have to create icons for the palette-selector buttons. These are kept in the icons subdirectory. You need two icons: mypaletteoff.svg and mypaletteon.svg, where 'mypalette' is the same string as the entry you used in instantiating the Palette class. Note that the icons should be the same size (55x55) as the others. (This is the default icon size for Sugar toolbars.)