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Purpurina ("Glitter" in Portuguese) is an open-source device for light-painting photography. It can be used to create beautiful and surreal images, using the light as a paintbrush over the photographed scenario.

These are the first images for project Purpurina, a low-cost light-painting device:

(Hello! If you can't read Portuguese, click here for the english version of this page)

O que é?

Purpurina é um dispositivo eletrônico projetado para auxiliar fotógrafos a criar incríveis imagens surreais usando light-painting.

Next month we're going to have a huge culture festival in São Paulo called "Virada Cultural". It takes a whole weekend, filled with several events spread around the city. We, at Garoa hackerspace, submited some ideais to take part in this festival and we're accepted. Since it's a rare oportunity to spend the night in São Paulo's downtown with relative safety, I was planning to create a light-painting stick and go for photo session into the streets.

Light-painting sticks are really simple things. Just a bunch of leds stuck on a stick that you move in front of a slow-shutter camera. So, I was planning to make one that could be programmed to display whole images after the stick movement. This concept isn't new at all. The MechatronicsGuy had published a tutorial on how to reproduce it's LightScynthe project: A 2 meters stick holding 64 leds, which was called "The Coolest Light-Painting Device Yet" by Gizmodo.

Have you ever seen someone making a drawing on an oscilloscope screen? Did you ever wanted to? Well, now you can. And, by "now", I'm not saying that you need to buy some hardware or mount some hacking device to create your drawing. "Now" is right now.

Let me introduce you to Rabiscoscopio: A simple and free software that convert your drawings into oscilloscope images.

Several times, on a computer projecting system, we don't have the projector and the projection screen correctly aligned. Some times we don't even have a flat (plane) screen. Other times we wan't to join the images of many projectors in order to comprise a single, larger image.

Many modern video projectors provide the means to adjust the image to fit on a tilted wall, but these adjustments have their limitations. Fortunatelly for you, your boss and co-workers, these things are not a big problem when you're just watching a PowerPoint presentation. But, some times, the image quality is mandatory. For example, when you're on a flight simulator, you want full immersion. If the images you see are distorted or not perfecly aligned, your brain won't believe you're on flying capsule, thousands feet above earth. And, if you're inside an flight simulator, you want your brain deluded be the images your eye see!

So, let's say that you want to project the following image

Update: This page was blogged on Hack-A-Day on Jan, 8. Since then I've received some comments and tips and modified the original sofrware. Now, after a game-over, the circuit enters on a demo mode, and keeps the waiting until someone hits "START" button. Better user interface!

These days I've found an old Dance-Dance-Revolution-Similar-Pad and was looking for an idea to hack it into something more usefull or, at lease, fun. It wasn't hard to find that someone already did an Arduino library to read a PlayStation controller. You can find it here. Best regards to it's author, Bill Porter.

My idea to reuse the PS2 controller was to recreate the game Simon.

Simon was a very popular electronic game among 80's kids. Brazilians knew it by the name Genius. There was also a toy-robot called Percival, that came with this game on top of its head.

This is a memory game. It plays a sequence of colored-lights and sounds, and the players have to reproduce the same sequence. Each colored-button is attributed to one player, and this player is responsible to press this button at the right time.

 This project is quite simple and easy to reproduce.

The code, that you can see below, uses 4 digital output pins to light the leds that represent the game sequence. It also uses one extra digital output to generate sound via a piezo-buzzer.

PlayStation controller also needs 4 digital pins, plus a ground and the 3.3 V power.

The hardware is very simple: Just 4 leds with their respective resistors and 1 buzzer. I glued everything inside an used ice-cream package, which received 4 different colors of paint to resemble the original Simon

 And here is the video of this rig in action:

Drawdio is a simple but really cool electronic circuit designed by a guy called Jay silver.

It's an sound generator where the frequency is controlled by de resistence of any material you connect at it. Even yout body! It's a simple and fun machine to produce cool sounds.

The original circuit is attached to a pencil. Since graphite conducts electricity, the sound frequency will change according the tickness of your drawing. You can also use the resistence of you body, water taps and other electricity-conducting materials to generate sounds

Check this video: A piano I drew with Drawdio

There are several versions of Drawdio around the internet. You ca find some of them in the links at the end of this page.

Links:

• Project on Garoa Hacker Clube featuring the modified version (Portuguese)
• Jay Silver's original Drawdio
• Lady Ada's version

Later in 2011 I've spent some weekends working on my first Android game, Junior. Now I've got some free days during Christmas/New Year holydays and decided to make a web version of the same game. 

Junior is a really simple game, based on a scrolling world. You comand an sperm (Junior!) accross the uterus, seeking for the egg. By touching or releasing the Android touch-screen, you control Junior's floatation, helping him to travel with touching the walls of mucus. It he gets stuck on the mucus, he dies. The oficial page for the Androind version is here

I've spend several days working on this game later this year, as it was my first experience with Android

As I have some friends that never played the game, because they don't own an Android phone, I've decided to implement a web version. I should, then, choose between Flash and HTML5. As I had a previously and sad experience with Flash (As every other Flash programmer, I believe), HTML5 won.

The HTML5 game code is totally new. I've simply coded a new game based on the original, like I was a new person without access to the original code. For example, the algorith to draw the scenario is totally different. Besides that i spent just ONE DAY coding it. Ok, it's a really simple game, but I've strugle with the f$@#$#$cking Android garbage collector for some weekends before finishing the original version. And now, with new code, with a new tecnhology, it was just a single day. Man, HTML5 is really the future :)

Below is the actual game. You can play it here, or go to it's oficial page, where you can find more info and instructions (I hope you don't need instructions. It should be a simple game!)

You may have noticed that digital cameras, including webcams, can detect infrared lights. If you point an TV remote controller to a recording camera, you can see a white spot of light coming from the remote.

My idea was to use this light to control the cursor on a computer screen, enabling me to draw on screen using the remote controller.

On the other end of the remote controller system, i.e. the remote received, we usually have a redish transluced piece of plastic. This plastic is a IR filter, that filters out all the other light sources, so the received behind it receives only the IR commands. So, I chopped a piece of this plastic, put in front of the webcam and... Voila! The camera became an infrared position detector!

Now, with a simple dedicated software, I can detect the position of the remote, related to the borders of the camera image. With a simple rule of three, I can detect where the user wants to draw.

The video below shows the result of this experience. Sorry, but it need to be seen on high resolution, to compensate the dirty-cheap ilumination i've used during recording.

The webcam I used was so old that I can't event find its drivers for Windows 7. I'm planning to teste again on a new - AND FASTER - camera.