Thymio for light painting

This page summarizes the baccalaureat project of Mariane Brodier Lorsque l'artistique et la robotique ne font plus qu'un at the Collège Rousseau of Geneva.

Purpose of the work

The aim of this work was to mix Robotics and art to create original figures. To do this, I used the robot Thymio II. The idea was to program the robot to execute a given trajectory, and then add colours (all this thanks « Aseba Studio ») so that the total trajectory creates a geometric figure that is pleasant to see, original, creative and with a meaning. To capture this geometric figure in a picture, I used the "light painting" technique, which uses long exposure in photography.

Nice examples of light painting are under:

The light painting technique

The « light painting » is a technique based on long exposure photography. Long exposure is a process that allows a movement to be captured in a static image. It is used especially to generate « blur » of natural spaces, such as streams, clouds, waves… A long exposure is often used to make pictures of the lights at night, and thus give the impression that it is illuminated as in daylight. This technique in photography manages to give this effect by bringing several pictures of the same scene made in a relatively long period (at least a second) together in a single photograph: this will create a « sum » of all photographs taken by the camera in this period of time. To do this, you simply need to have a DSLR camera that has the function known as « Bulb », which allows the shutter to be opened and closed manually; the latter is like a curtain that one decides to open by pressing the capture button and close when released. When it is opened, the sensor of the camera is therefore exposed to the light during a time that one can choose: « Bulb » mode offers from 1 to 30 seconds, but you can choose the manual option where it will be the user who chooses the time during which the shutter is open. This manual operation will be used for the work, because 30 seconds are not enough to be able to capture the whole trajectory of the robot.

The « light painting » uses this type of technique, except that instead of capturing a natural movement of objects or people, this will be used to capture the movement of a moving light source. The « light painting » is a long exposure photography technique which takes a picture of the movements, in a dark space, of a source of light. It is the path of the light source that « paints » the outline of a figure directly into the camera. The « light painting » needs a very slow shutter speed, usually at least one second.

In my work, I captured the various colours of the robot LEDs. To do this, I installed my camera on a tripod and I took photographs in a darkroom:

chambre.png

I decided to make 20 pictures, divided into 4 sequences, as follows:

First sequence: Multicolour

These are mixtures of geometric shapes, assembled to give a final form. All colours are used in sequence.
The first two images in this series are the first ones I programmed, the first having been programmed at the EPFL during my training on the « Thymio II » robot.

multicolor1.jpg

All these images are done with a state machine controlling motor speed and colours. For instance this first figure is done with the following code (here the file as it uses a constant):

var parti   
var itera = 0
timer.period[0]=1000

onevent timer0
    if parti==1 then 
        itera = itera + 1 
        if itera==1 then
            motor.left.target = -200 
            motor.right.target = 200
            call leds.top(16,16,0)
        end
        if itera==2 then
            motor.left.target = vitesse_avant
            motor.right.target = vitesse_avant
            call leds.top(22,10,0)
        end
        if itera==3 then
            motor.left.target = 240
            motor.right.target = -240
            call leds.top(32,0,0)
        end
        if itera==4 then
            motor.left.target = vitesse_avant
            motor.right.target = vitesse_avant
            call leds.top(16,0,16)
        end
        if itera==5 then
            motor.left.target = -200
            motor.right.target = 200
            call leds.top(10,0,22)
        end
        if itera==6 then
            motor.left.target = vitesse_avant
            motor.right.target = vitesse_avant
            call leds.top(0,0,32)
        end
        if itera==7 then
            motor.left.target = 240
            motor.right.target = -240
            call leds.top(0,16,16)
        end
        if itera==8 then
            motor.left.target = vitesse_avant
            motor.right.target = vitesse_avant
            call leds.top(0,22,10)
            itera = 0
        end
    end

onevent rc5
    if rc5.command==32 then
        parti=1
        itera=0
    end
    if rc5.command==33 then
        parti = 0
        motor.left.target = 0
        motor.right.target = 0
    end

The robot is started using a remote control (easier to start in the dark).

multicolor2.jpg

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multicolor3.jpg

The following image has been programmed only with colours (« call leds.top(r,v,b) »), therefore without movements; in order to make this picture, the robot oscillated at the end of a wire that unrolls itself.

multicolor4.jpg

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multicolor5.jpg

Second sequence: Tangram

For this sequence, I was inspired by the Tangram, a Chinese puzzle that comes from splitting a square into 7 basic parts: five triangles, a square and a parallelogram. The robot being able to make only lines or curves, I could program the outline of several puzzles.
I chose five puzzles of animals, and I associated colours to them: yellow for the bird, pink for the cat, red for the horse, blue for the rabbit and green for the turtle.

tangram3.jpg

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tangram4.jpg

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tangram5.jpg

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tangram2.jpg

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tangram1.jpg

Third sequence: Circles

For this sequence, I based my work on the « crop circles » that are often attributed to aliens. The colours used are gradients, except for the first where I used basic colours, therefore the red, green and blue for the three basic colours of LEDs and yellow because it is one of the primary colours, in addition to red and blue.

cercles5.jpg

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cercles2.jpg

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cercles3.jpg

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cercles4.jpg

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cercles1.jpg

Fourth sequence: dotted

This sequence looks much like the first, except that instead of using all colours, only two colours are alternated making dotted lines. At the beginning, I wanted to use only one colour and create simple dots, but having to turn on and off the lights almost every second gave a quite blurry rendering of little interest. Thus, I alternated two colours, to remove the blur effect.
In addition, this sequence is the last I made (except the first image, which was supposed to go in the first sequence), therefore the trajectories are much more complex that in the first sequence, with the picture no. 5 being the most complex program of all my work.

points1.jpg

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points2.jpg

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points3.jpg

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points4.jpg

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points5.jpg

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