Small Stella Manual

Last updated 2nd August 2008.
The latest version of this manual can be found online at http://www.software3d.com/StellaManual.php?prod=small.

Contents

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 http://www.software3d.com/Forums.

Built-in Polyhedra

The program includes Platonic, Archimedean, Kepler-Poinsot and Johnson solids, some Stewart toroids, 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. 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 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 another way to select a model.

You may also open a separate window for looking through the built-in list and choosing a specific model. To open the list, use menu item "File->Polyhedron List...", hit Ctrl+N, or click the equivalent button on the main toolbar. A window opens showing a list of categories on the left, and a list of models from the current category on the right. Select a category, then select a model, and click OK or hit Enter. The selected model and its net should appear on the screen. The categories are as follows:

Finally, if you know the symbol or name of the model you want, you can enter it directly. Again, open the polyhedron list ("Poly->Polyhedron List...") and you'll find a text entry field at the top. Type in the symbol or name of a polyhedron. 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:

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.

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 mode. 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).

Navigation

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.

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:

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.

Selecting Faces and Vertices

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

Faces may be selected by pointing the mouse at them and double Left-clicking or doing Shift+Left-click. The selected face is highlighted in white and will partly show through other faces (try rotating the model so that the face is on the other side). Only one face may be selected at a time. Many operations work on the current face, which is either the selected face, or the most recently selected face if no face is selected. If you have not yet selected a face, then the first face is the current face.

Vertices may be selected by pointing the mouse at them and double Right-clicking or doing Shift+Right-click. The selected vertex is highlighted with a white dot, and half of each surrounding edge is also highlighted. These show partly through other faces. This also selects the corresponding face of the dual model, which will also become highlighted if you have a dual view open. Selecting a vertex is useful in a few situations, such as when you have a vertex figure view open and want to choose which vertex figure to look at.

Faces and vertices can also be selected via the Info window.

Toolbars

There are four toolbars arranged in three rows, with two in the last row. 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

There 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 toolbar 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, the radius, and the volume.

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

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 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).

You may 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).

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 six types of view which show smooth morphing between a model 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 two 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 appears to be an error, but isn't really.

Nets

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. Nets are laid out differently for printing from how they appear on the screen, in an attempt to fit as many nets onto each page as possible. You get a dialog full of options for printing nets, but you can ignore most of these to start with and just click on "Preview" (or hit Enter).

Folding Nets

There's also a Folding Net view. This can show you 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, which means 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, 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:

Submenu: "Nets->Net/Paper Color Mixing"

This submenu 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 pieces, and you are currently viewing a yellow piece in the Unfolded Net View, then printing will only print yellow nets. It will print all the yellow nets though, not just the one you are viewing, and it will try to pack them all together as best it can. The print-preview lets you see how many pages there are, so you just put that many pieces of yellow paper in the printer tray (use manual feed for thicker paper and to reduce curling). Then you use PageUp or PageDown to change to a net of another color in the Unfolded Net View, and print again with different colored paper, and so on for each different color.

Scale

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. Here's what the items on this menu do:

Undo/Redo

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.

Advanced Topics

Showing Vertices and Edges

The following options are available for controlling the display of vertices and edges. They are found on the "Display->Vertex & Edge Options" submenu. All settings are remembered after you exit the program for next time.

Hiding Faces

The Display menu includes a group of items for hiding or showing faces. Most of these require you to select a face first (see Selecting Faces and Vertices). Note, the hidden attribute of a face can also be copied quickly between faces using the mouse. See Color/Hide Faces Mode.

Colors

Models may be colored in various ways. This section describes the items on the Color menu.

Images

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).

Cross-Sections

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 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

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").

A good web page showing the different symmetry groups is http://newton.ex.ac.uk/research/qsystems/people/goss/symmetry/Solids.html. The only groups missing here 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).

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. All edges of the selected type are cut/uncut at once. Nothing is really ever "glued", just either forced as a cut or not.

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. If you didn't want those faces to connect, then you can always cut their shared edge too.

For example, use this mode and 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.

Measurement Mode

Menu item: "Selection->Mouse Selection Mode->Measurement Mode"

This mode lets you measure the distance between any two vertices of a model. Use Shift+Left-click on a couple of vertices and the distance between them is shown in the status bar. If you continue to click on other vertices, the value shown is always the distance between the last two vertices chosen. A line is drawn between the vertices so that you can see exactly what distance is being measured. If instead you use Shift+Right-click on a series of vertices, the distance between the first and last one is displayed, rather than the last two. This is convenient if you want to measure the distance from some vertex to several other vertices.

In addition to appearing in the status bar, 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 model used for printing nets.

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

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. Ctrl+Left-click on a face to copy attributes from the previously selected face. Shift+Left-click on a face to change all faces of that type according to the attributes of the previously selected face (use "Options->Maintain Reflexibility" to choose whether reflected faces should also be changed). In either case, hold the left mouse button down and draw the mouse across multiple faces to apply the color/image to all of them, like painting.

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).

Ctrl+Right-click and Shift+Right-click both just select a face without changing its color. This lets you choose a new face to start copying attributes from. In this mode, the face is only highlighted white briefly when you select it, and then returns to its normal color, since it is important to see true face colors in this mode.

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.

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. Use Shift+Left-drag to move an image on a face. Use Shift+Right-drag to scale an image on a face. Use Shift+Left+Right-drag to rotate an image on a face.

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).

The operations listed above (including Ctrl+Left-click, which doesn't otherwise affect the image) all perform another function too. They change the main face of the image. The main face is the one that is used to control the projection of the image. This only has an effect when "Image->Project onto each Face Separately" is disabled. The image lies parallel to the main face and is projected down through the model in the same way for all faces. So these mouse clicks let you change which face is used for the projection.

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.

Credits

Small Stella was written by Robert Webb.

I use FreeImage (http://freeimage.sourceforge.net, 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 http://www.mayang.com/textures

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 © 2001-2010, Robert Webb ().
Stella Home Page: http://www.software3d.com/Stella.php.