GUI Introduction

When you first start / see the main LDCad GUI / interface you probably notice it's quite different from most modern CAD programs. There are multiple personal and technical reasons, I won't go into here, for this though. Anyhow don't let the "oldschool" look fool you, just take the time to get used to it and you might just love it.

A clean LDCad installation will look something like this at its first start.


By default the screen is divided into five regions, namely: A toolbar, The color bin, The part bin, The editing area and a status bar.


The toolbar can be split into two sections, namely: menus and buttons.


The default menus shown in the toolbar are:


  • File, used for top level file io
  • Session, used for managing the single LDraw model/part currently being worked on.
  • View, used for managing the views (sub windows) inside the working area.
  • Select, used for (mass) selecting parts in the current model.
  • Scripts, used to access scripted features (macros/animations).
  • Prefs, used for configuration settings.

The shown menu items can be customized through the prefs/GUI menu.

As menu's inside LDCad are very different from other software I will discuss the menu system in more detail later on in this chapter.


The buttons on the tool bar represent actions you can perform on, for example, the model you're currently working on. From left to right these actions are:


  • Open LDraw file
  • Save the current LDraw file
  • Save all open LDraw files
  • -
  • Undo
  • Redo
  • -
  • Cut
  • Copy
  • Paste
  • Copy paste options
  • Go to the fist building step of the current model
  • Go to the previous building step of the current model
  • Go to the next building step of the current model
  • Go to the last building step of the current model
  • Add a new building step to the current model
  • -
  • Go to the main model of the current LDraw file
  • Add a new model to the current LDraw file
  • -
  • Group the current selection
  • Set the center of the current selected group
  • Ungroup the current selection
  • Hide the current selection
  • Undo the last hide
  • Undo all hiding
  • -
  • Reset the selection center
  • Numerical selection move
  • Numerical selection rotation
  • Numerical selection center move
  • Grid options
  • -
  • Add selection to favorite colors
  • Add selection to favorite parts

Most of these actions should be reasonably self explainable, the others will be addressed in other parts of the documentation.

The shown buttons can be customized through the prefs/GUI menu.

Color bin

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The color bin is used to select the color of the LDraw part you want to add to your model next. This is done by first choosing a group of colors, e.g. "solid plastic" or "transparent".

Lets click on "solid plastic", the color bin will change accordingly and will now display a color wheel holding a collection of colors usually used with solid plastic LEGO bricks.

Placing parts in LDCad is always done using the last used color or "working color". Clicking on one of the color wheel's segments (e.g. the red one) will change the current working color to the color it displays.

Doing so will also change the first rectangle of the bar at the bottom of the color bin. This isn't that weird as that rectangle shows the current working color. Besides the current working color the bottom bar will also show a couple of previous used colors inside the rectangles at the right of the working color one.

Clicking on any of the last used colors will make it the working color again, and clicking on the working color it self will apply it to the current selection but more about that will follow later in the documentation.

While working with colors you will occasionally need a color from a different group e.g. transparent or rubber. To select such a color you could navigate back to the main list of groups using the arrow in the top left of the color wheel. And then select needed group of colors.

But the intended way of LDCad is to do this by using a second "view" into the color bin. Views are controlled by the numbered tabs at the top of the color bin. Clicking e.g. "2" will make that view's currently used group the active one. By default it will also be at the top level and thus listing the main color groups. Now choose "transparent" so it displays a color wheel again.


You can now set the working color to any transparent color using this color wheel. And when you need a solid color again you only have to change back to view "1", by clicking its tab. You can setup six views this way and as a result you probably never be more then two clicks away from finding and using a needed color.

Getting the hang of the color bin and its views are an essential part of LDCad usage, so feel free to play around with it for awhile.

Part bin

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The part bin is somewhat similar to the color bin as it also uses views, but instead of lists of color groups it displays a grid containing either links to groups or things you can actually place in your LDraw model (like parts and models).

The easiest way to understand this is by thinking about the part bin like a tree, by clicking the cells you zoom in on a branch which itself could again hold a number of branches until you reach the leaves (parts).

After a fresh start the part bin will display the root group containing a number of top level groups like in the picture at the left. These groups are (from left to right top to bottom): Sorted parts, Categorized parts, Set inventories, The search group, Overview groups, Special parts, Templates, Favorite parts and Part usage history. The exact meaning of these groups will be discussed later in the documentation using more meaningful examples.

In order to get the hang of the part bin itself lets just click the first (top/left) one. The content of the grid will change into something more familiar, a collection of LEGO bricks. This is the root of the "sorted" branch, which offers access to all LDraw parts in a more friendly (in regards to the default LDraw categories) way.

All the items in the "sorted" group are links to more specialized groups. For example the first one (2x4 brick) will navigate you to the "bricks" branch which will lead to more and more specific kinds of bricks. The "technic gear" cell on the other hand will lead you into the technic parts department sort to speak.

Lets navigate to a group containing actual parts. By clicking the "2x4 brick" cell in the "sorted" group. This will open the "bricks" group listing a number of sub sets of bricks, lets choose the first one again (a 2x2 brick this time) bringing us to the "plain bricks" group containing actual LDraw parts (see right picture) you can use in your models. Parts can be used in your model by dragging them into the model, you will learn all about that in the editing oriented parts of the documentation.

As the bin now only shows "plain bricks" you probably need to navigate to another branch group soon in order to place e.g. a plate or sloped brick into your model. This can be done using the arrow in the first cell of the grid it will navigate back to the higher branch/group you came from. When at the appropriate level you side step into a different (e.g. plates) branch until you get to the intended collection of LDraw parts.

But as with the color bin the intended LDCad way of working with parts is by using multiple views in order to quickly switch between e.g. plates and bricks. Switching to e.g. the second view will instantly put you at the bin root again as it hasn't been used yet. Try to navigate view 2 towards "normal plates" yourself to get the hang of it. Afterwards you'll see you now can add both bricks and plates to your model by only switching between view 1 and 2 of the part bin, and there are four more views you could point at something useful (e.g. the search group).

Final thing I would like to point out about the part bin at this point is its filter functionality available at the top. When you point the mouse at the area now displaying "[no filter]" (without clicking) you can limit the number of items shown in the grid by typing a text, e.g. "clip".


Doing so will cause the grid to only show items containing the word "clip" in them. Clicking the little icon on the right will reset the filter again. Clicking on the left icon or the filter text it self will open a more advanced filter dialog opening up additional options.

Editing area

By far the most important part of the LDCad interface is the editing area. But because there currently no files open it will be empty and as an alternative the "getting started" window will be shown.


This handy window lists the most common tasks needed in order to get going with a LDraw model. It will also list a couple of the LDraw files you used recently so continuing work on them is just a click away. But as we are still in a freshly installed state there will be none listed yet. However the window will let you start a new model or helps you open one of the example models packed with LDCad.

Just for kicks try to open the 5571 model by clicking on "Open an example model" followed by clicking "5571.mpd" in the resulting menu. It will load the LDCad mascot model you've probably seen on the "welcome" page of this site.

With an active model displayed the editing area will look vastly different and probably infinitely more interesting then the stuff discussed so far. As editing models is the main function of LDCad, discussing its inner secrets is therefore too big a subject to do in this general GUI introduction. It will of course be handled in depth in the more editing orientated parts of the documentation.

Status bar

The main goal of the status bar at the bottom of the program is to display a hint about whatever is below the mouse cursor at the moment. In this example the mouse is over the "File open" icon of the toolbar. The hint also includes a hotkey if one is available for this action.


Besides the hint it will also show some performance information concerning rendering at the left, and the coordinates of the mouse location on the current editing grid at the right.

The menu system


As mentioned above the menu system inside LDCad is different from most other programs as it has been designed for productivity. This means you can keep any menu window open if you need one of its items multiple times in a row. You keep a menu open by pressing the "pin" button at the right top as seen on the image at the left.


Also different from familiar menu systems is the option to navigate to other menus while reusing the current window. This is possible because all menus are internally linked in a big tree whom are always available even if the thing they control isn't in context. If this is the case most or all of the items in the menu will greyed out.

You navigate into a sub menu by pressing any item with a ">" icon besides it moving up a level is done by pressing the arrow button at the left top of the menu. You can also go right to the menu root by clicking the small house button also at the left top. Finally any menu can be closed by pressing the "X" button at the right top, do note non pinned menus will close automatically whenever you click outside the window or the clicked item demands it.

In practice you won't need to navigate around in menus much as most of the time you open a relevant one by right mouse button clicking. Doing so will open a context related menu based upon the place you clicked and the state of your working area.

The items shown in a menu can be of four different kinds, namely:

  • Click, executes an action (e.g. open a file from disk).
  • Toggle, controls the current state of an option (e.g. grid rendering on/off).
  • Toggle list, also controls the current state of an option, but through multiple items representing one state each.
  • Submenu, navigate into another menu further down the menu tree.

Clicking a "click" item will close a non pinned menu if the associated action succeeded. All other item types won't close a menu even when non pinned.

Finally all items will show the hotkey currently set for it.

If you feel the menus are too big, you can reduce their size from the pref/gui menu, resulting in something like shown at the right.

The window system


As described above the default layout of LDCad contains three working area's or sub windows, namely: Part bin, Color bin and editing windows. You can resize all of them using the horizontal and vertical separation lines in between them. The two bin windows can also be "undocked" which would put them on top of the other windows, This is done by grabbing the window at its dead space (e.g. the space to the right of the "6" view label).

Once undocked the color bin window will look something like the picture at the right. You can resize this window by dragging its sides and move it around by grabbing it at the top bar. You can dock the color bin window again by holding down the CTRL key while holding the window roughly at the top of the part bin.


It is also possible to add additional color and part bin windows to your working area. This is done trough the View menu accessible from the toolbar. Click it and inside it click on the "New part bin window" item. This will add a new undocked part bin window at the current mouse location, like the one in the picture at the left. You'll notice it has a horizontal orientation, this is because currently its width is larger then its height.

Personally I often dock a second part bin window at the bottom of the screen for use with the special part bin groups like MPD navigation, but you will learn about that in a later chapter so for now just close the extra part bin window by clicking its "X" at the right top.

You might also have noticed the "Source window" in the view menu which is the fourth kind of window inside LDCad, it purpose and inner workings are handled elsewhere in this documentation.

Once you are happy with the current layout of windows it might be a good thing to "lock" them into place to prevent accidental undocking. This can be done from the prefs/GUI menu.

What's next

The above is all you should need to get familiar with the general GUI of LDCad. Once you are comfortable with the above topics feel free to continue on to the next page: Basic editing, in which we will actually be drawing something.