Small Stella Manual

Last updated 29th March 2020.
The latest version of this manual can be found online at


Getting Started

This manual contains instructions to get you started using Small Stella. It covers most features, and after reading this document you should be able to find your way around most of the interface.

If you get stuck, feel free to ask questions on the Stella forums at

Or follow Stella on facebook at

Built-in Polyhedra

The program includes Platonic, Archimedean, Kepler-Poinsot and Johnson solids, some Stewart toroids, compounds, and other models.

The default window layout has two views side-by-side, showing the base polyhedron on the left and its net (or one of its nets) on the right. The default base model is the icosahedron.

Use the Right and Left arrow keys to change to the next/previous model in the built-in list (or the menu items "Poly→Next Polyhedron" and "Poly→Previous Polyhedron", or the green left and right arrow buttons on the main toolbar or at the top of some views). Note: if you have loaded a .stel file, then the arrow keys move forward and backward through files in the same folder instead. Furthermore, the arrow keys, unlike the green arrow buttons and menu items, are context sensitive. That is, they behave differently depending on what type of view is currently active. If the current view has yellow arrow buttons at the top, then they performs the function of those instead (e.g. changing to the previous/next net if the unfolded net view is active). See more about yellow arrow buttons later. You can also use Ctrl+Left and Ctrl+Right to go to the previous/next model, regardless of the selected view (they behave exactly like the green arrow buttons).

The built-in list is divided into a hierarchy of categories. You will see the current category and model name displayed in the main toolbar. Clicking on either of these names opens a list of other categories or models to choose from, providing a more direct way to select a model.

The categories are as follows:

Polyhedron Search

Another way to find a polyhedron is to use "File→Polyhedron List...", hit Ctrl+N, or click the matching button on the main toolbar. This opens a window listing all the polyhedra provided. A list of categories on the left, and a list of polyhedra from the current category on the right. The list of polyhedra has several columns, including the primary symbol, name, and the number of faces, edges, and vertices. The list may be sorted according to any column by clicking on the header of that column. Click a second time to reverse the order. To return to the original order, click on the header of the first column.

Select a category on the left, then select a polyhedron on the right. Information about the selection appears at the bottom, including other common names, dual names, Wythoff symbol, Wenninger number and page number in Wenninger's books Polyhedron Models and Dual Models where the model can be found. Click OK or hit Enter to open the selected polyhedron.

Rather than looking through the list, you can enter a symbol or name directly in the Search field at the top. Symbols for uniform polyhedra may be any of the following:

Other models use different notations. For example, enter "J4" for the square cupola, one of the Johnson solids. This provides a very quick way to jump to a particular Johnson solid if you know its number.

You may also enter the name of a polyhedron. It can be either the full name (including known alternative names and dual names), a substring in the name, or an abbreviation for the name using either the first letter from each word, or the first letter from each part of each word. Some examples:

As you type into the search field, you'll notice it finding the best match as you go. Hit Enter to load a model as soon as it finds the one you're after.

Below the search field is a choice between Find one and Find all. So far we've been using the default, Find one, which means the first match is found. Find all finds all matches, and lists them in the special Search Results category at the top of the category list. Select an item from the list and open it. Now you can use the Left and Right arrow keys (or green arrow buttons) to step through the search results.

To the right of the big Search field are some smaller fields where you can enter face, edge and vertex counts. If you enter a number, this also becomes part of the search. For example, enter "12" in faces, and only polyhedra with 12 faces will be found. A range may be entered, such as "12-24", to find all polyhedra with between 12 and 24 faces. You may enter values into more than one field to further narrow the search. Comprehensive tooltips help explain how to use each field, so hover the mouse them to find out more.

With the Search Results category and Find all selected, another button appears labelled ←Locate search result. Click this to locate the selected polyhedron in its original category.

Dual Polyhedra

Every polyhedron has a dual, which won't be explained fully here, but you may think of it as the model's opposite. It has the number of faces and vertices swapped with respect to the original model, and the same number of edges. The dual of the dual brings us back to the original model again.

Hit "d" to switch between the base polyhedron and its dual. The net will also change.

.stel Files

At any point you may save a model you like to Small Stella's native format, the .stel file. Everything about your scene is saved here, including your current screen layout and views, the model itself, various settings, and the state of mouse inertia. The latter means that if your model is spinning, morphing or folding etc. when you save it, then it will be spinning, morphing or folding again when you reload it.

Use "File→Save" or "File→Save As" to save your model, and "File→Open" to re-open it later. In the file browser that appears, select an existing .stel file to see some information about it in the preview area at the bottom of the browser. You will see the number of faces, edges and vertices, and the first line of the comment field from the Info Window if one has been set.

Tip: Any .stel files saved from Small Stella before version 5.0 will need to be loaded and re-saved in order to support this information preview in the browser.

If you particularly like a model, you may make it load immediately when Small Stella starts up by using "File→Save Default Scene". Next time you start Small Stella, this model will load automatically. You may even use this just to set up your view layout the way you like it.

Mouse Tips

The mouse does many different things, depending on what mode you're in, which view you're in, whether you're holding down the left/right/both mouse buttons, and whether you're holding down Shift/Ctrl/Neither/Both/Space. Watch for the tips in the bottom right hand corner, which show you what the mouse buttons do in the current situation. The tips change when you hold down Shift/Ctrl/Neither/Both/Space. They may also change when you move the pointer from one view to another. Even I forget what the mouse can do in some modes, so these on-screen tips help a lot!

Sometimes just clicking is required (e.g. Shift+Left-click to select a face). Sometimes dragging in 2D is required (e.g. Left-Drag to tumble the polyhedron). And sometimes dragging in 1D is required (e.g. Right-Drag to zoom in/out).


All basic navigation is done with the mouse and no need to touch the keyboard, except for some less common movements. These mouse controls generally continue to work in different modes too.

In a 3D view:

Tumbling and twisting both have mouse inertia, so you can release the mouse buttons while dragging and the model will continue to tumble or twist. To stop it, perform the same action again, but clicking instead of dragging the mouse (e.g. do Left-click to stop tumbling). You may also hit Esc to stop any mouse inertia.

Similarly in a 2D view:

With 2D views, zooming zooms in on the point where the mouse was when you first clicked the right button, so you can zoom in on a specific point. As with 3D views, twisting has mouse inertia.

A couple of more advanced navigation controls are available in 3D views. Hold down the Space bar and you'll notice the mouse-tips in the bottom right corner change:

If you find that you want to pivot around a selected axis more often than twisting, select "Options→Right-drag to Pivot Around Selected Item" (or matching toolbar button). This swaps the operations of Right-drag and Space+Right-drag.

You may also switch each view between perspective and orthogonal projections by ticking/unticking "View→Orthogonal View" (keyboard shortcut: O). Perspective views are what we see in the real world, where things closer to the camera appear to be larger. Orthogonal views are like architectural plans, where distance from the camera does not affect the apparent size of objects.

Finally, you can use items on the "View→Camera" submenu to store and recall camera positions. The field-of-view and perspective/orthogonal setting are also stored.

Exploding Polyhedra

The faces of polyhedra may be exploded apart as follows: This can be useful for examining the internal structure of faces that would otherwise be partly or entirely hidden.

Exploding has inertia, so if you release the mouse button while still dragging, the exploding will continue at the current rate. It will remember how far apart the faces are and use this as one extreme in the explosion. So faces will explode out to this point, then turn around and implode again. The other extreme, at the imploded end, is determined by the following menu item:

Exploding faces is available in most 3D views, but not the Unfolding Net view.

The "Esc" key

You can hit Esc to cancel all sorts of things. It performs the first appropriate action on the list below.

Selecting Faces, Edges and Vertices

In the default mouse selection mode (see below), faces, edges and vertices may be selected with the mouse.

Face, edge and vertex types can also be selected via the Info window.

Tip: When an edge is selected, its length is shown on the status bar at the bottom of the window.


There are five toolbars arranged in three rows, with two in the first and last rows by default. They may be dragged and docked to different sides of the window, or dragged away into a separate window. Their positions will be remembered between sessions. The toolbars are:

The buttons all have tool-tips, so if you place the mouse over a button and don't move for a moment, a small description of the button appears.

In addition, there are further buttons in the top right corner of each view. The buttons that appear depend on the type of view. Yellow left or right arrow buttons are for changing to the previous or next item that this view type can display. For example, in the 2D net view, these buttons cycle through the various nets required. If the current view has yellow arrow buttons, then you can use the left and right arrow keys on the keyboard to perform the same function.

Polyhedron Information

The Info window is a special window for displaying information about the current polyhedron. There are three ways to open or close it: via the "View→Model Info" menu item; via the equivalent button on the options toolbar; or by simply hitting "i" on the keyboard.

Information includes number of faces, vertices and edges, number of edges that must be cut/folded/glued to make the model, alternative names for the model (if any) and lots of other info. It is presented in a tree structure, where collections of similar data are grouped together. A small "+" or "-" sign beside each item may be clicked with the mouse, allowing each section to be expanded to show all the data in that group, or collapsed to hide the data. Which groups are expanded or collapsed is remembered between sessions, so the data presented will always be the data of most interest to you.

You can Right-click on information that may be edited to edit that item. Most items can't be edited, but ones that can include the model's name, the dual's name, comments about the model, internet link associated with the model, radius, surface area and volume.

Expand the face, edge or vertex counts to see a list of face, edge or vertex types. You can Left-click on a type to select a face, edge or vertex of that type in the main view. Similarly, when a face, edge or vertex is selected another way, the matching entry in the Info window will be highlighted.

The Info window also shows how many parts belong to this compound (or "1" if not a compound). Expand this item to see a list of the polyhedra in this compound. Left-click on one to select a face belonging to that part.

This window starts off docked to the right hand side of the main window, but like the toolbars, it may be dragged to dock elsewhere in the main window, or dragged away into a free-floating window of its own. The position is remembered between sessions.

Views and Layouts

By default there are two views, one showing the base polyhedron, and one showing its net. You may choose a different layout with "View→Choose Layout", or more conveniently by using Ctrl+1 to Ctrl+6, depending on how many views you want. For example Ctrl+4 will give you a four-view layout. Repeatedly hitting Ctrl+4 will cycle through all the different four-view layouts available.

Once you have the layout you want you can choose what kind of views are shown by selecting each view in turn (by clicking in them or on their title bars) and hitting one of the buttons on the view toolbar (or choosing from the bottom section of the View menu).
Tip: To see which view is selected, look for the one with the highlighted title bar. There's always exactly one selected view.

When you save a .stel file (not available in the demo) your layout and view types are also saved, and restored when the file is opened another time. If you wish to open a file without changing the current view layout, use "Options→Keep Layout when Opening Files". Once ticked, you may continue to open further files without the layout being affected.

Dual Morphing

There are eight types of view which show smooth morphing between a polyhedron (or compound) and its dual. Select one of these view types from the view toolbar, or from the "View→View Duals Morphing" submenu. Use Ctrl+Left-Drag to morph between the base and dual in these views. There's also mouse inertia on this function, so you can release the mouse button while dragging and the morphing will continue on its own.

Note: the demo version will not allow morphing for certain models.

This morphing may not act perfectly between all pairs of models. Some methods cause parts to get flatter and flatter until they disappear, which produces a visual jump, but isn't really wrong.


Another type of view is the Unfolded Net view. Use PageUp and PageDown to move through the list of nets required. Hit Ctrl+P to print the net (or to print any other view type, but make sure you have the appropriate view selected first!). The demo version will only allow you to print nets for the five Platonic solids, but it will still let you see a print-preview of nets for any model. The Net view shows one unfolded net at a time, but when printing, all required nets are included. Small Stella attempts to pack as many onto each page as it can to minimize paper requirements.

Printing must always be done via a print-preview, to avoid any issues with unexpected settings. A dialog box appears first full of options for printing nets, but you can ignore most of these to start with and just click on "Preview" (or hit Enter).

If you're not sure about how to put the nets together, then look for the "Edge connection IDs" tick-box in the dialog box that appears when you print nets. Ticking this will cause numbers to be displayed beside each edge around the net. Each number will appear exactly twice among all the nets. Find the matching numbers to see which edges should be glued together. This is especially useful for models with asymmetric color schemes, where the nets may go together in various ways, but only one has the correct colors.

When printing, if the sale of the model is too big for nets to fit on your printer's paper size, an error is given, with an offer to scale the model down just enough so that the nets fit. The message also shows the factor by which the model would be scaled down.

See Scale for details about printing nets in different sizes.

Folding Nets

The Folding Net view shows the nets in 3D, folding up into the final model and unfolding again into separate flat nets. Use Ctrl+Left-drag to interactively fold and unfold the nets. Mouse inertia applies here too, so if you release the left mouse button while still moving the mouse, the folding/unfolding will continue on its own at the current rate.

When unfolding, first the folded nets move apart from each other (if there's more than one net), then they each unfold individually. Ctrl+Right-click jumps to the point between these two stages, or just folds the net half-way if there is only a single net.

The "Nets→Nets Shown in 3D View" submenu gives you control over what is shown in the Folding Net view. Your options are:

If you want to try something more unusual, try creating the convex hull of a partly folded net using "Poly→Create Convex Hull" with the Folding net view selected!

Separating Net Colors

You may want to print all nets onto white paper, perhaps using a color printer to fill in the face colors or images, or you may want to print nets of different colors separately in order to print directly onto colored paper (my usual technique).

The "Nets→Net/Paper Color Mixing" submenu allows this. It contains the following options:

When mixing of colors is not permitted within nets, only nets of a single color will be printed at any one time. For example, if there are red, yellow, and blue parts, then you will need to do three print-outs to print all the nets, one for each color. If you are currently viewing a yellow net in the Unfolded Net View, then by default, printing will only print yellow nets, but the dialog box has a drop-down list for choosing the paper color you want. For the chosen color, all nets of that color will be printed, not just the one you are viewing, and it will try to pack them together as best it can. The print-preview lets you see how many pages are required, so you just put that many pieces of red, yellow or blue paper in the printer tray (use manual feed for thicker paper and to reduce curling on some printers).


In order to glue parts together when building a paper model, tabs are usually left on some or all edges around each net. The following construction methods are common: Most people seem familiar with the single-tab method, and indeed it's how I first started, but for the most part I recommend the double-tab method for the following reasons: The single-tab method can still be useful in the following cases: You may mix and match methods within one model. In such cases I would start by attaching the single-tabs, which are harder to glue once more of the model takes form.

Small Stella supports all three methods, or a mix of them. Tabs are shown in both the Unfolded and Folding Net views. Use the "Nets→Tabs" submenu to state your preference. With an edge selected, the preference applies to that edge only. With no edge selected, you will be setting the default preference. It contains the following options:


Before printing out nets, you are going to want to decide how big to make your model. This is what the items on the "Scale" menu are for. They let you change the scale of the whole model by specifying the length of certain features, such as edge length or radius. Note: the model does not get bigger or smaller on the screen, but printed nets will reflect the change in scale. However, if you have tabs on your nets, then you will see them change size. Visually, they scale in the opposite direction to the change you make, because while the model might be physically bigger, it remains the same size on the screen, so the tabs which have remained the same physical size, are therefore shown to be smaller.

Tip: You may enter an equation rather than a simple number if you wish.

Here's what the items on the Scale menu do:


Tip: When entering a scale, or entering a real number in any other part of the interface, you may enter an equation rather than a simple number if you wish. Examples of equations include:


Most operations can be undone and redone, including changing to a new model, changing the scale of the model, and changing face colors and images. Use "Edit→Undo" (keyboard shortcut: Ctrl+Z) to undo, and "Edit→Redo" (keyboard shortcut: Ctrl+R) to redo. Both operations are also available on the main toolbar. If you Right-click on either button, you'll see a menu of the last 20 operations that can be undone/redone. Select one to perform multiple undos/redos in a single step.

See also "Edit→Undo Settings" for various options that control the undo mechanism. You may limit the amount of memory used, and the number of undo levels available.

Full Screen Viewing

Expand any view temporarily to become full-screen using F2 or "View→Full Screen". The active view then takes over the screen and all menus, toolbars and borders are hidden. It can be nice to view models this way with no other distractions. To exit this mode, hit F2 again, or hit Esc. Any operation that opens a dialog box will also force an exit from full screen mode (e.g. opening a file with Ctrl+O).

3D Stereoscopic Display

Geometry may be viewed in true stereoscopic 3D! To enable this, select from the "Display→3D Stereo Display" submenu. Two slightly different images will be rendered, one for each eye, giving the model a 3D appearance. If you load a background image ("Image→Load Background Image"), it will appear to be pushed back behind the model.

If you have red/blue or red/green glasses, you may use those. Even with red/blue glasses, try the "Left Red, Right Cyan" option as it may work better than the "Left Red, Right Blue" option. If you're after some red/blue glasses, there are some available for under $3 including shipping here.

The other option is to display the two images for your left and right eye side-by-side. You have the option of putting them either way around. This option has the advantage of maintaining full-color images and not requiring glasses, but requires the user to be able to blend the two images themselves, either by going slightly cross-eyed, or by allowing their eyes to drift apart slightly. For the cross-eyed option, try holding a finger to the screen, pointing up, with the tip between the two images, then pull the finger slowly towards yourself. Keep your eyes focused on your finger but be aware of the two images behind it. There will be a point where they overlap behind your finger. Now try to keep those images fused and slowly take your finger away.

Personally I find the parallel-eyed version much easier to achieve and to keep focused. For this, try to look past the screen into the distance and focus far away. Then try to look down to the screen while keeping your eyes focused in the distance. Again it is a matter of then trying to merge the two images.

Advanced Topics

Animated Transitions

When changing from one polyhedron to another, the transition may be animated, and there are plenty of ways to customise this. You can control what kind of transitions is used in different situations, as well as adjusting parameters governing how each type of transition behaves.

Tip: You can skip a transition at any time by hitting Esc.

The first two items on the Options menu relate to transitions:

The Transitions dialog box has a great many options for customising transitions, but you needn't understand them all. If you just want to change the type of transition, or the length of each transition, then make sure "Occasion" is set to "Default", and change "Method" or "Duration" accordingly. See below for a list of methods available.

The Transitions dialog box is modeless, meaning you can leave it open and still use the rest of the program. This lets you see what effect changing settings has without closing the window.

If you want to get into more detail, here's what the Transition dialog box provides:

Tours (Polyhedral Slideshows)

A tour is an animated polyhedral slideshow. For example, you may start with a cube folding and unfolding, then switch to a dodecahedron morphing into its dual and back, and so on. You may choose the transition to use between each event, and may even transition between 3D and 2D views.

Tip: You can stop a tour from playing back by hitting Esc (or by hitting the play button again).

A tour consists of a list of events. Each event may have its own model, view layout, and transition to the next event. Tours can be saved and reloaded from .tour files.

The Tour menu provides various controls for creating and editing your tour. The Tour toolbar provides another way to access all these same controls. The menu contains the following:

The tour list shows all the events in a list, one per row. You may drag items within the list to rearrange them. You may click on an event to select it, and use Ctrl+Left-click to select multiple events. The list has columns, each showing different information about each event, including:

You may Right-click on the tour list to open a menu with a few relevant options:

Showing Vertices and Edges

Overall display of vertices and edges may be enabled or disabled. They may be shown either as points and lines, or spheres and cylinders respectively. All settings are remembered after you exit the program for next time.

Tip: To hide or show individual vertices or edges, see Hiding Individual Faces, Edges and Vertices below. Options for controlling the overall display of vertices and edges are found on the "Display→Vertex & Edge Options" submenu:

Hiding Individual Faces, Edges and Vertices

The Display menu includes a group of items for hiding or showing individual faces, edges or vertices. Most of these require you to select a face, edge or vertex first (see Selecting Faces, Edges and Vertices).

Tip: Make sure you have overall display of vertices and/or edges enabled, or they will always be hidden.

Tip: Vertices and their dual faces are hidden in sync. So when you hide an individual vertex, it will hide the matching dual face too.

When a vertex or edge is selected, the text in the menu items below will have "Face" replaced by "Vertex" or "Edge" as appropriate. The relevant items from the Display menu are as follows.

Note, the hidden attribute of a face can also be copied quickly between faces using Color/Hide Faces Mode.


Models may be colored in various ways. This section describes the items on the Color menu. See also Color/Hide Faces Mode for rapidly spreading colors across selected faces.


Images may be put on faces. You may want photos of your pets on the faces of a dodecahedron, or you may want a model to look like it's made of wood. This section describes the items on the Image menu (see also Image mode below).

Geomag-Style Rendering

Rendering in Geomag style makes polyhedra appear as if they were built using the Geomag magnetic construction kit. Generally Geomag-style rendering will be permitted unless a model could not be physically built using Geomag, in which case a reason will be shown on the screen. Some common polygons not available from Geomag are subdivided using ones that are.

Control Geomag-style rendering via the "Display→Geomag" submenu (or matching toolbar buttons):

When selecting face colors, you will be limited to those available for Geomag panels.

If images are applied to the faces, these will appear as if using Geomag's Deko panels. When printing the unfolded net view, only the parts you require for use with the Deko panels will be printed, ready to cut out and insert into the Deko panels.

A collection of models suitable for construction with Geomag can be found in the Geomag Library folder within the Stella library.


Select a view and use "View→View Diagrams→Cross-Section" or the matching toolbar button to switch to the Cross-Section view. This shows a 2D cross-section (or slice) through the current polyhedron. The cross-section is made with a slicing plane, which can be controlled in various ways. Any edge of the original model passing through the plane is sliced to become a vertex. Any face crossing the plane is sliced to become one or more edges (nonconvex polygons can lead to more than one edge). And a whole polyhedron is sliced to create one or more polygons. So each entity loses one dimension as a result of the slicing process. Note: many edges and faces may lie entirely on one side of the slicing plane, and so do not contribute at all to the cross-section.

Cross-sections have a beauty all of their own, especially when animated by altering the slicing depth (keeping the slicing plane parallel, but moving it through the model). The slicing depth is a value between 0.0 and 1.0, each representing a plane at opposite ends of the model.

Each polygon of the 2D cross-section is surrounded by edges formed by slicing faces. The edges are shown in the color of their corresponding face, and the polygon itself is filled with a color obtained by averaging the colors of its surrounding edges, weighted by their edge-lengths. This can produce some pleasing results, with the polygon colors changing smoothly into other colors as their edges get longer or shorter. When multiple polygons overlap, the overlapping colors are also blended, making even more interesting images.

More colorful cross-sections can be obtained by using "Color→Basic Color Scheme→Color Along Cross-Section Direction", especially for regular polyhedra, which would normally be shown all in one color. When all faces have the same color, the detail of the cross-section can be lost since all edges and filled regions become the same color. With this option, cross-sections become much more colorful, but still retain full color symmetry.

The mouse may be used in the following ways.

The Section menu offers further cross-sectioning options:

The yellow left/right buttons in the title bar of the Cross-Section view also serve a purpose. They skip the slicing depth forward or backward to all the values where the slicing plane passes through a vertex of the original model. These are often quite interesting points in the transition.

Finally, the slicing plane can be tumbled interactively in a free-form style. See Cross-Section Tumble Mode for the details.


Symmetries are transformations which leave a model looking like it hasn't moved. They mostly come in two types: rotational and reflective. Use "Display→Show Symmetry Axes" to display the rotational symmetry axes (keyboard shortcut: S, also on options toolbar). In 3D views these are indicated by an axis through the model with a small disc at either end. The number of spokes in the disc indicates the order of rotational symmetry. The different types of rotational symmetry axis are shown in different colors.

Use "Display→Show Reflection Planes" to display the reflective symmetries (keyboard shortcut: R, also on options toolbar). In 3D views these are represented by great circles around the model in the reflection plane.

The symmetry group of a polyhedron is the collection of all its symmetries. The options toolbar has a field that shows the rotational symmetry group (e.g. "Icosahedral"), and another field showing the reflective symmetry group within that (e.g. "Horizontal Reflection"). To the left of these is another field showing two common symbols used for the current symmetry group: Schönflies notation, Orbifold notation, and Coxeter notation.

Read about symmetry groups and their notations at

Another good web page showing the different symmetry groups is The only groups missing from this site are icosahedral symmetry, both with and without reflections. The h subscripts on that page correspond to "Horizontal Reflection" in Stella, and the d subscripts correspond to "Diagonal Reflection". Notice that the rotational symmetries of a tetrahedron can be combined with either of these reflection types (Th and Td). The latter is the symmetry group of the regular tetrahedron, while the former is known as pyritohedral symmetry.

Mouse Selection Modes

Submenu: "Selection→Mouse Selection Mode"

Items in this submenu allow you to enter a different mode, where the mouse behaves differently from normal. Exactly one of the items will be selected at any one time. The first item on the list is the default mode, so to exit one of the other modes, either select this item, or just hit Esc. There is also a toolbar containing a button for each of these modes.

You can tell when you're in a different mode from usual by holding down Shift and seeing what shape the mouse pointer becomes. Navigation with the mouse acts the same in all modes. The difference is what happens when you're holding down Shift and/or Ctrl.

Some of these modes are described in the following sections.

Cut/Uncut Edges Mode

Menu item: "Selection→Mouse Selection Mode→Cut/Uncut Edges"

If you don't like the net created, you can force the program to cut certain edges. This makes it rebuild the nets, connecting different faces together instead.

Uncutting an edge does not guarantee the faces will be attached in the net, just stops them from being forcibly cut.

Note that cutting one edge may cause other faces to join together in a net where they were previously not connected. This is because the nets are rebuilt from scratch. So you can use cutting as a way of forcing other faces to join up, but only indirectly. If you didn't want those faces to connect, then you can always cut their shared edge too.

As an example, use Shift+Left-click on an edge of the icosahedron. All edges are the same type, so they are all cut, so you end up with only one face in each net. Use Shift+Right-click instead to cut just one edge.

Measurement Mode

Menu item: "Selection→Mouse Selection Mode→Measurement Mode"

Measurement Mode lets you measure the distance and angle between any two items, where each item may be a plane, line or point. The distance and angle are shown on the screen, and the items highlighted in light blue, along with some construction lines to help clarify what's being measured. Items may be defined via the mouse:

So use Shift+Left-click to select a vertex, edge or face, and then again to select another and see the distance and angle between them. If you want to specify an item that doesn't correspond to an existing entity, such as a plane through three arbitrary vertices, then you can build up this plane by specifying each vertex in turn. Use Shift+Left-click for the first one, then use Shift+Right-click to add the others. You can even specify a plane through an edge and a vertex by Shift+Left-clicking the first and Shift+Right-clicking the second.

Normally at most two items are remembered at a time, and the distance and angle measured between them. So when you specify a new item, the oldest item of the previous two is discarded. You can use Ctrl instead of Shift with the above mouse operations if you want to replace the most recent item rather than the oldest. This retains the earlier item, so is handy if you want to fan out measurements from the same point repeatedly.

These is one occasion where three items are remembered rather than two. This is when you select three vertices in a row. The distance between the last two is shown, along with the angle subtended at the middle point.

You may also specific a point at the centre of the model, even when there's no vertex there to click on. There's a button which appears on each view's title bar when in Measurement Mode to achieve this. It shows a circle with a dot in the middle. This allows you to measure distances from the centre of the model. Or you can use it as the first point in a line or plane through other arbitrary vertices or edges by using Shift+Right-click as above.

In addition to appearing on-screen, the distance and angle are shown in the status bar at the bottom of the window. You can also access the currently measured distance via "Scale→Measured Distance". This also lets you change the distance, which affects the scale of the whole model, as used for printing nets and some other operations.

Note, you may only click on true vertices of the model, not virtual ones caused by intersecting faces.

Aside from measuring things, Measurement Mode has other uses. The most recently defined item may be used in the following ways:

Color/Hide Faces Mode

Menu item: "Selection→Mouse Selection Mode→Color/Hide Faces"

This mode lets you easily copy colors, images, or "hiddenness" between faces.

In either case, you may hold the left mouse button down and drag the mouse across multiple faces to apply the color/image to all of them, like painting. No need to click on each one.

If the selected face was hidden, then the "hiddenness" is copied, that is, other faces may be easily hidden too by Ctrl+Left-clicking on them. In this case the color/image of the face is not changed (it is presumed that it is only the hiddenness that you are interested in copying).

If you plan to do a lot of augmentation (see below), this mode can be useful. One of the options when augmenting is to only augment faces of the same color. So select one of the faces you want to augment, then copy that color to all the other faces you want to augment. This lets you quickly and easily select a collection of faces for augmentation.

Face colors may also be changed in various ways via the Colors menu.

Image Mode

Menu item: "Selection→Mouse Selection Mode→Image Mode"

If the selected face does not already have an image on it when entering this mode, a file browser will open allowing you to select one. This is the same as if you had used "Image→Load Image" (see Images above). You may cancel the file browser if you wish to use Image mode without loading any new images.

Image mode lets you accurately position images on faces however you want.

Compare these three operations with navigation in a 2D view. Notice the similarity when you don't hold down Shift? This makes it easier to remember which combination of buttons does what.

Use Ctrl+Left-click to select a face without affecting the image on it. And use Ctrl+Right-drag to stretch an image on a face (changes the aspect ratio of the image). Note: when using spherical or cylindrical mapping, the image must always wrap all the way around, so scaling and stretching the image both have the same effect, to scale it vertically, but leave it wrapped all the way around horizontally.

Use Ctrl+Shift+Left-click to swap images between two faces. The images are swapped between the face you click on, and the face that was previously selected. This is useful in conjunction with "Image→Load Image List...". You can load a bunch of images at once, then swap them between faces to get the arrangement you want.

Cross-Section Tumble Mode

Menu item: "Selection→Mouse Selection Mode→Cross-section Tumble Mode"

This mode allows you to interactively tumble the slicing plane. See Cross-Sections for more information and ways to choose specific orientations of interest for the plane.

In this mode, the mouse can be used in the following ways.


Small Stella was written by Robert Webb.

I use FreeImage (, under the FreeImage Public License version 1.0) for importing 2D images, which in turn uses various other libraries. Below is a list of credits regarding these libraries:

Wood and stone textures obtained from

The End!

Hopefully you'll be able to work the rest of the interface out on your own! There are lots of menus to look through. Let me know if you have any problems or can't figure out how to do something. I'll be interested to hear what you think!

Copyright © 2001-2023, Robert Webb
Stella Home Page: