Modeling with LeoCAD

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Ivonne Wierink,

Ivonne Wierink,

Building Blocks

Putting together realistic models on a computer screen can be useful and fun. LeoCAD

Older generations may still remember playing with wooden blocks or using sand to build castles and roads. Others may have played with model train sets. But, building things came into its own with Lego. Lego pieces are made from colorful plastic and fit together with a grid system of knobs and holes.

Lego has been around since 1947 and is manufactured by the Danish toy company Lego Group [2]. Competitors have used the idea to create a smaller market segment but their products don't always work with the original.

Originally intended for children, Lego is now used by young and old alike. Different sets have been specially designed for specific age groups. The older the target group, the smaller and more versatile the individual bricks. (See the "Legos and Electronics" box for more information.) The biggest advantage here is that you can always combine all of the bricks from one product line together. This means that you can bring your own ideas to building with Legos and develop your skill as a builder.

Legos and Electronics

Since about 1996, electronic components have been included in some Lego series. In the beginning, these were called Lego Technical Computer Control. This product line moved into the Robotics category around the year 2000 and is now sold as Lego Mindstorms.

A constant theme has been to have a basis for programming and controlling components such as motors, lights, and pneumatic elements. Originally dubbed Robotic Command Explorer (RCX), it has been sold under the name of Lego Mindstorms NXT since 2006. NXT is programmable in Python with the NXT-Python [3] software package.

Since 2013, the control brick product line has been called Mindstorms Evolution 3 (EV3), and it is still compatible with NXT. Both NXT and EV3 use the same hardware base and both have an ARM processor.

Linux software is packaged into these products and can be used with Debian GNU/Linux by changing the memory card [9]. A parallel product development by the name of ev3dev [4] lets you incorporate prepared images for Linux, Mac OS X, and Windows.

Fond Memories

If you are waxing nostalgic for a beloved set of building blocks from your childhood, you may have already searched through your attic or storage room. Even if you are lucky enough to locate them, however, you may find that there are not enough pieces to build the project you have in mind.

Just as in the building trades, replacement parts can be expensive, especially because they may become rare after a while. Pick a Brick [5] is a good source for replacement parts. This is a Lego service that lets you order individual parts in almost every color and amount, even for sets that may no longer be sold. BrickLink [6] is also a good source; it is an international dealer platform for bricks and models.

Clicking a Model Together

For those of you who are considering drawing up construction plans, it is a good idea to take a look at the software packages that might help you with the process. LeoCAD is an open source graphical program that can be used to click together a model you have designed on a display screen. LeoCAD is easy on the budget, and it also saves the time and frustration of waiting for real-life bricks to be delivered.

LeoCAD also offers the advantage that you can work with an unlimited number of virtual building bricks. However, the program requires some patience and skill from a user so that the bricks can be placed in the correct position for anchoring.

The starting point is placing the model inside a three-dimensional space. LeoCAD has all the tools you need to rotate the model on each axis in the space you have chosen. It also allows you to zoom in, create a background image and lighting effects, and prepare the model data for further processing by rendering programs such as POV-Ray, WaveFront, and 3D Studio [7].

In addition to LeoCAD, you will need the LDraw library [8]. At first glance, this library appears merely to add considerably to the bricks available in LeoCAD. However, LDraw also designates one of the open standards for Lego CAD programs applicable to the creation of models together with their assembly instructions and animations. Unfortunately, this software is not available with an open source license.

You will find ready-made packages in the repositories for Debian GNU/Linux and Ubuntu. LDraw is located in the Idraw-parts package [9] in the non-free area or multiverse. These can be easily installed using the package manager on your system. You can start LeoCAD via the Unix command of the same name.

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