Modeling with LeoCAD

What Is LeoCAD?

LeoCAD is a GUI program with three operating components. These include: (1) a bar that sits at the top for icons and the menu; (2) a centrally located model image with a coordinates system in the form of a grid; and (3) a selection area containing a list, a rotatable preview of the bricks together with a search box, and three color palettes on the right.

The palette includes both standard and mixed colors as well as a transparency option. The three color palettes are labeled as "solid colors" (top), "special colors" (bottom), and "translucent colors" (in the middle). There are no restrictions for using any of these colors for any of the bricks.

The program offers access to most of the actions via menu entries and via icons. Below, I use a small Tux model to introduce the capabilities step-by-step which LeoCAD offers. The Tux is shown as a mascot because this is how it was presented at the Linux Days 2015 [10].

The center piece of your work consists of the model image sitting in the middle of the program window. At the beginning, this will show an empty, transparent surface with knobs. The dimensions of the grid will automatically adapt to the size of the model.

The first step in constructing the penguin (Figure 1) is to create the characteristic yellow feet. To do this, go to the selection area for the color palette labeled "solid colors" and select the corresponding square. Then, select a 2x3 plate from the "plate" category and add this to your model via Ins. As an alternative, you can use the menu entry Piece | Insert or the icon with the gray building block that is to the left of the lightbulb.

Figure 1: First phase of construction.

You will now need three white bricks for the belly of the Tux. Two of the bricks should be 2x2 in size and tapered. The third brick should be a plate that fits in between. Then, select white from the color palette and then choose brick "Slope Brick 45 2x2 inverted."

To retrieve this brick, you will need to enter "inverted" in the search box of the selection area as a filter. Only entries that include the text " inverted" will appear. The search is case-insensitive. Empty spaces are significant. Apparently, LeoCAD processes an entry as a single character string.

After you have added this brick to the model image via Ins, you can use the blue double arrow to rotate the brick around the vertical axis and into position. This is done by clicking with the left mouse button on the blue double arrow and holding the mouse button until the brick is rotated 90 degrees to the right and it fits into the grid. Then, use the left mouse button to click on the vertical blue arrow and drag the block downwards until it sits flush on the yellow plate. The process is similar for the "Plate 2x2" brick and the "Slope Brick 45 2x2."

The back and the two wings of the Tux are black. Thus, you need a "Brick 1x2," a"Plate 2x1," and two "Slope Brick 33 3x1" for the two wings. To position all of these bricks correctly, you should rotate the model by 90 degrees clockwise. This is done by clicking on the icon with the circle and the three arrows. A circle with four squares will appear. These four squares are used to effect rotation around the appropriate axis. Hold down the left mouse button to execute the rotation (Figure 2). This lets you view the model from all sides to find the ideal position for adding these bricks.

Figure 2: Second phase of construction.

The final step here is to finish the head of the Tux. The head consists of three small 2x2 plates – two black and one yellow – a black 1x2 brick, a small black 1x2 plate, and two white 1x1 bricks together with eyes made from "Brick 1x1 with Headlight." The eyes consist of two round plates in black – "Plate 1x1 round" – that you should put on the front of the two white bricks. You can see the results in Figure 3.

Figure 3: Third construction phase.

After finishing, you should save the model as a file or export it in another format via (File | Export ). Options for export formats include Renderer, HTML/PNG, the comma-separated values format CSV, and a combination for the e-commerce platform Brick Link [6].

Tools and Aids

LeoCAD also has a small number of very useful tools and aids that can make the construction process easier. The menu entry View | Viewpoints can be used to change the angle of vision and perspective of your model. Views are available for the front, back, sides, top, and underneath.

When used along with the guidelines and the grid, these views are helpful for orienting an object in a multi-dimensional space. These views also simplify construction of the model. By using the menu entry View | Projection , you also can switch between a perspective in which the planes are displayed and a uniform perpendicular perspective. Your choice depends on which is more helpful for you.

Three icons are used to control the movement of the model pieces. The icon showing a grid with lock blocks movement and prevents the accidental shifting of the bricks. The grid with red dot icon lets you snap a brick in place at the intersection points on the axis and move a brick along segments of an axis that are equal in size to half the length of the brick. Using the angle with magnet icon lets you restrict angular steps to one rotation. Unfortunately, it is not possible to determine from the icons which state is currently active.

You can move a selected brick very precisely along its X,Y, and Z axes, by using the icon showing a red dot with arrows, and the three entry fields next to it. For this activity, movement by one brick length approximately corresponds to the value of 0.8 on an axis.

To move an individual brick or a group of bricks along a particular axis, you should use the icon with the four arrows. The three colored arrows that were presented in the discussion of the first construction phase will appear on the brick. The next icon over – the arrow with circle – lets you rotate around one axis.

You can manually move the entire image with the help of the icons. Here, it is good to have a sensitive touch, because the control element is set very precisely. Zoom lets you get a closer look at the model. If you only want to enlarge a rectangular-shaped subarea, use the icon with the magnifying glass set into a square.

If you open up a rectangle with the mouse, then all of the bricks found inside that rectangle will be highlighted. You can add the highlighted sub area to a named group via Piece | Group or by using Ctrl+G. You can then use this new group again in the modeling. In other words, you can move, rotate, copy, and delete it.

If you want to remove a brick, select the eraser icon and then click with the left mouse button on the brick you want to remove from the model. The color bucket is used to change the color of a brick. A left click on the brick coats it with the color that was earlier specified via the color palette.