Category Archives: Software

StippleGen: Weighted Voronoi stippling and TSP paths in Processing

grace2k-2

One of the perennial problems that we come across in a variety of contexts, including CNC artwork and producing artwork for the Egg-Bot, is the difficulty of creating good-quality toolpaths– i.e., vector artwork representing halftones –when starting from image files.

One of the finest solutions that we’ve ever come across is Adrian Secord’s algorithm, which uses an iterative relaxation process to optimize a weighted Voronoi diagram, producing a set of points (stipples) that can closely approach the appearance of a traditional stipple drawing.

Another important technique is “TSP art,” where the image is represented by a single continuous path. You can generate a path like this by connecting all of the dots in a stipple diagram. Designing a route that visits each dot exactly once is an example of the famous Travelling Salesman Problem (or TSP). From the standpoint of toolpaths (for the Egg bot and most other CNC machines), a “TSP” path is even nicer than stipples, because little or no time is spent raising and lowering the tool.

Today we’re releasing a new program, StippleGen, which can generate stipple diagrams from images, using Secord’s algorithm. StippleGen saves its files as editable, Eggbot-ready Inkscape SVG files, which can in turn be opened by other vector graphics programs, or re-saved as PDF files for use in other contexts. It can also generate a TSP path from the stippled image, and either save that path as an SVG file or simply use that path as the order of plotting for the stipple diagram.

StippleGen is free and open source software, written in the Processing development environment. It comes ready to run on Mac, Windows, and Linux, and it is available for download now.

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PeggyDraw 2

peggydraw2

 

We are pleased to finally release PeggyDraw 2, a little bit of long-delayed software. It’s a Processing application that you can use to draw simple 1-bit animations on a 25×25 grid. The neat bit, of course, is that you can press the “Save” button, and the file that it saves is actually an Arduino program, ready to be programmed onto a Peggy 2.

 

You can download PeggyDraw 2 right here. It’s fully built in Processing, so that it works on Mac, Windows, and Linux. Also, open source, designed to be adaptable.
Some things to note about this program:

 

  • If you don’t have Processing on your computer, download it here.
  • The editing interface is easy point-and-click. Try it out to see how it works.
  • You can individually pick different delay times per frame, as low as 20 ms, or give every frame the same duration.
  • The frame data is stored in Arduino program memory, so you’re only limited by the flash memory in terms of frame number– over 250 frames fit on an ATmega328P.
  • The output file is located in the PeggyDraw2 sketch directory, inside a directory named “PeggyProgram” “data.” The file is called “PeggyProgram.pde.”
  • You can both save a file and later reload it for editing.
  • The formats used in PeggyDraw 2 should be easily adaptable to write sequences for other types of LED grids, even of different aspect ratio and control software.

And, special thanks to Matt Mets, http://cibomahto.com for assistance with Processing.
Update, 3/19/2011: We’ve posted a new version, PeggyDraw 2 v. 1.1, available here. Note that the output file is now stored in the “data” directory, not a separate “PeggyProgram” directory.

SymmetriSketch: A simple app for playing with symmetry

We were recently contacted by a mathematics instructor, who suggested that it might be interesting to have a program like Snowflake, but with the option of picking and choosing different symmetry properties.

Natural snowflakes have (approximate) sixfold rotation symmetry plus reflection symmetry. However, a lot of things that you can draw by hand have absolutely no resemblance to snowflakes at all– and it is somewhat fun to explicitly play with the rules.

Our new program, SymmetriSketch, sticks to the same basic design principles as Snowflake: it’s cross platform, open source, and able to export a true vector drawing with a closed path. However, SymmetriSketch is a much more flexible program that allows you to play with different symmetries, and create all kinds of different things that would never be mistaken for frozen water.

Here’s what it looks like when the program first opens:

SymmetriSketch 1

The initial shape is an overall pentagon– an object with five-fold rotation symmetry and reflection symmetry. The figure is generated by taking the editable slice– highlighted here and when you start the program– and reflecting and rotating it to complete the full shape that you see.

Within the editable slice, you can also see three highlighted control points that can be dragged around. There is control point at every vertex and at the midpoint of every line segment between two vertices. If you drag a control point that is the midpoint of a line segment, it turns that control point into a new vertex. That new vertex also gets new control points at the midpoints to its neighbors.

Every vertex point can be moved to any location on the screen with the exception of the vertex that is initially at the top point of the pentagon– that vertex is constrained to move along the vertical axis– the axis of reflection symmetry.

SymmetriSketch 6

The controls are purposefully kept simple. There are two symmetry controls– for the order of rotational symmetry and to toggle reflection– which you can change in the lower left hand corner of the screen.

The number, with its +/- controls, refers to the order of discrete rotational symmetry. If the number shown is n, then n-fold rotational symmetry is applied, which means that the displayed object is unchanged when rotated by 360 degrees/n. In the screenshot above, 9-fold rotational symmetry is applied.

Orders from 1 to 99 are allowed– note that 1-fold rotational symmetry is “no symmetry at all” since it requires 360/1 = 360 degrees of rotation to return to the original shape.

The second control is for reflection symmetry, and toggles between “reflect” or “rot. only,” where it either does, or does not apply a mirror reflection across the vertical axis.

SymmetriSketch 3

With reflection symmetry turned off, the figure is drawn with pure rotational symmetry. (This screenshot was taken while editing the shape, and you can see control points, indicated by little circles.)

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Programming Meggy Jr RGB

Last week we released an Arduino environment library for the Meggy Jr RGB. The code is an open source project here, and the downloadable package comes several example programs, ranging from very simple to moderately complex. (One of the examples is a new game called Froggy Jr, where you help your a little round green frog cross the street and then a river.)

Today, to make it all a bit more useful, we are releasing the Meggy Jr RGB Programing guide, which you can download Here (600 kB PDF file).

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The Peggy Strikes Back

Automatically generated Peggy Code

Today we have an update on our Peggy 2.0 Light Emitting Pegboard project, with (1) a new and improved version of the Peggy2 Arduino library, (2) links to several awesome examples of Peggy hacks– including a full-motion video hack, and (3) a new GUI application example that lets you display an image on the Peggy without writing a single line of code.
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An Arduino library for Peggy 2

Peggy 2 Gray Side

Here we describe a basic-function Arduino library for Peggy 2.0.

Note: This article describes the new 0.3b version of the library, dated 7/8/2008.
The original article at this location has been archived here.

The Peggy 2.0 Arduino library brings Peggy 2.0 up to the level of having useful compatibility with the Arduino software environment: you can use high-level commands to control what shows up on the Peggy display. For example, the type of high-level command might be something of the form “SetPoint(x, y)” which would turn on the LED located at position (x,y) in the grid.
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Archived: An Arduino library for Peggy 2.0

Note: This article is out of date but archived here for future reference.
You can find the current version here.

 

Today we present a basic-function Arduino library for Peggy 2.0.

This brings Peggy 2.0 up to the level of having useful compatibility with the Arduino software environment: you can use high-level commands to control what shows up on the Peggy display. For example, the type of high-level command might be something of the form “Peggy_SetPoint(x, y)” which would turn on the LED located at position (x,y) in the grid.

Continue reading Archived: An Arduino library for Peggy 2.0