Building a digital lego with LeoCAD

Apps & Software

Building virtual blocks is almost as fun as the real lego. Not only do you have all the little stones you can think of with LeoCAD, you can also easily convert everything you do digitally into instruction drawings. For example, your children can recreate your virtual constructions in real life.

Tip 01: Download

LeoCAD brings the child up in us. It is an open source application (read: free), available at leocad.org for macOS, Windows, and Linux. In contrast to the classic building boxes, this virtual building set provides you with an endless number of blocks in endless variations and colors. The idea is to position the blocks on the 3D canvas that looks like the typical lego building board. Interestingly, you can save the structure as an instruction plan to reconstruct afterward with real lego. In addition, LeoCad is compatible with the LDRaw standard. This has the advantage that you will find a lot of models on the internet in the .ldr format that you can further customize. That way you can build on other people’s designs.

Tip 01 On the homepage of LeoCAD you see the London Tower Bridge, built with four thousand virtual blocks.

Tip 02: Work plane

LeoCAD opens with an empty building surface. The dot pattern is meant to estimate the distances between the blocks. At the top are the menus and work buttons and on the right, you have the enormous library with parts, arranged in alphabetically ordered sections: Animal, Antenna, Arch, Bar and so on… By clicking on a part and then selecting a color from the palettes, you determine the tint of each part. There is also a search box to find parts faster, provided you know the name at least. That’s why you better click the right mouse button in the library and the options Medium icons and Show Part Names Selecting. You can also access the List Mode option via the right mouse button. That mode is even slightly clearer, but the list is getting longer.

Tip 02 The work surface with the dot pattern automatically adjusts when you make the construction larger.

The huge parts library is arranged in clear categories

Tip 03: The right place

To place a virtual lego piece, click the Insert button, the first red button at the top left. The simplest way is to drag and drop the block.

As you drag, you can see the contours at the place where the block will be when you release the mouse button. To move a piece, use the mouse pointer to move over the block. The cursor changes to a cross and above the object appear three arrows indicating the X, Y and Z direction in which you can move such a block: high/low, left / right and front/back. Hold the mouse pointer over the direction indicator you want to use until this arrow turns yellow. Then you can drag the block in the direction of the yellow arrow. With the same arrow trick, each piece also rotates in three different directions. Only you have to use the curved arrows. The arrow you have selected will turn yellow and you will immediately know which axis you can perform the rotation.

Tip 03 On the right side of the status bar you can read via the X, Y and Z values where you place the part.

Copy and paste

Often you need the same piece several times logically that you use the Copy and Paste command. Remember that LeoCad puts the pasted object in exactly the same place as the copied object. So you have to drag the pasted object to see this new piece. With the button Movement Snap, you indicate exactly how many balls you want to move the new object in the X, Y or Z direction.

You have to drag and drop copied elements; otherwise, they will remain over the original element.

Tip 04: Timeline

There is a tab under the library to go to the timeline. To pass on the construction instructions, you have to record the structure chronologically in steps. A step in LeoCAD is a collection of pieces that you have placed and in most cases consists of several intermediate steps. To place a new step, click on the double blue arrow in the toolbar. With the help of the blue arrows, you can go forward or back in time and gradually complete and reconstruct the construction. Instead of the blue arrow buttons, you can also hold down the Alt-key and use the left-hand arrows of your keyboard to go through the different steps.

Tip 04 In the timeline you follow the structure per step.


Soon you can export the step-by-step plan and even print it. This allows everyone to follow how your lego building has grown. That structure gets the viewer to see from the point of view that you use. For example, if you want to change something at the back or bottom, you will have to rotate the object. Yet you do not want all previous steps to be seen from the new perspective. That is why LeoCAD uses the technique of keyframing. This means that this keyframe will not place the previous and next steps in a different perspective. Turn on the keyframing mode by clicking the key in the toolbar.

Turn keyframing on so that the perspective of the next and previous steps does not change.

Tip 05: Viewpoint

Zooming is best done via the scroll wheel. The button with the magnifying glass called Zoom, you use to right-click to indicate which panels you want to see in the right-hand column: Parts, Colors, Properties or Timeline. To quickly and efficiently rotate the work surface with the lego construction, press the Alt-key so that you can click it with the mouse on the work-valk to turn it in all directions. This gives you a quick insight into how you can get the very precise view on all sides of your object with the Alt key and the scroll wheel. Via the View menu and the Split Horizontal and Split Vertical commands you divide the display into different panels so that you get the front, top, and side at the same time.

Tip 05 We view the construction from three perspectives at the same time.

You can view the front, top and side of your design at the same time

Minifig Wizard

Naturally, the child in us also wants to place lego dolls. You do not have to put that together from scratch. Via the menu Piece, you come to the Minifig Wizard. The number of combinations that you put together in this selection window is endless. Do you want a doll with a beard? Does the boy have to look happy or sullen? Does it wear a helmet? And again you can give each part a different color.

With the wizard, you compose a Lego doll yourself.

Tip 06: Output

If you are satisfied with the design, you can save the project as a .ldr .dat or .mpd file that you can edit with this program afterward. With the Save image command, you automatically save every step that the program has recorded in a folder to come to the construction. If your project consists of 24 steps, then you will find as many png files in the output folder. You can also indicate that, for example, you only export step 12 to 24 witl. Interesting is also the possibility to export as an HTML file. That way the result is one long HTML page that you can open with any browser and where you follow step by step how your building is composed.

Tip 06 The result is a step-by-step plan from the first block to the last.

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