Presentations¶

An Ipe presentation is an Ipe document with several pages (“slides”) that is presented using a video projector.

The following sections explain a number of Ipe features that are useful for making such presentations.

PDF or HTML/JS?¶

You have two choices for presenting Ipe presentations: PDF or HTML/JS

The classic approach is to save the Ipe document in PDF format, and use any PDF viewer to present it. One such viewer is the presentation tool IpePresenter that comes with Ipe. It shows the current slide in one window (which you can make full screen on the external display), while showing the current slide, the next slide, notes for the current page, as well as a timer on your own display. IpePresenter not only works for Ipe presentations, but also for presentations made with beamer. It easily fits on and runs from a USB-stick, and does not require Latex on the computer where you give the presentation.

The alternative approach is to save the Ipe document as an HTML/JS presentation. This produces a single HTML-file, which you can open in any browser. The HTML-file uses reveal.js and the animation library GSAP to implement navigation between slides, transitions, and animations. Note that in the current version this HTML-presentation will not work offline, as it downloads the Javascript-libraries when you open it. This presentation format supports various kinds of animations, see below.

Presentation stylesheets¶

A presentation must use a dedicated stylesheet. Presentations must use much larger fonts than what is normal for a figure. Don’t try to make use of the LARGE and huge textsizes, but use a stylesheet that properly defines normal to be a large textsize.

Ipe comes with a style sheet presentation that can be used for presentations. To create an Ipe presentation, open “Style sheets” (Shift+Ctrl+S), select presentation and press “Add”. Then select basic and press “Del”. (presentation is meant to be used instead of basic, not in addition to it.)

Note that presentation has a rather simple look. For a more sophisticated presentation style sheet, have a look at Jens’ webpage.

You will notice that in a presentation, only part of the “paper” is used for the contents. This smaller area is called the frame. The Insert text box function, for instance, creates text objects that fill exactly the width of the frame.

You can set a title for each page using Page ‣ Edit title & sections. It will be shown in a uniform style (defined by the style sheet) outside the frame.

Views¶

When making a presentation, one would often like to present a page incrementally. For instance, I would first like to show a polygon, then add its triangulation, and finally color the vertices. Views make it possible to do this nicely.

An Ipe document consists of several pages, each of which can consist of an arbitrary number of views. When saving as PDF, each view generates a separate PDF page (if you only look at the result in a PDF viewer, you cannot tell whether two pages are actually two views of the same Ipe page or two different Ipe pages). When saving as a HTML/JS presentation, the views of a single page become a vertical stack of slides in the deck.

An Ipe page consists of a number of objects, a number of layers, and a number of views. Each object belongs to exactly one layer. A layer can be shown by any number of views—a view is really just a list of layers to be presented. In addition, a view keeps a record of the current active layer—this makes it easy to move around your views and edit them.

Views can also give a different meaning to symbolic attributes, so that objects that appear in blue on one view will be red on the next one. One can also change the dash pattern and pen width, and can even replace one symbol by a different one.

Example¶

To return to our polygon triangulation example, let’s create an empty page. We draw a polygon into the default layer alpha. Now use Views ‣ New layer, new view, and draw the triangulation into the new layer beta. Note that the function not only created a new layer, but also a second view showing both alpha and beta. Try moving back and forth between the two views (using the PageUp and PageDown keys). You’ll see changes in the layer list on the left: in view 1, layer alpha is selected and active, in view 2, both layers are selected and beta is active. Create a third layer and view, and mark the vertices.

Save in PDF format, and voila, you have a lovely little presentation. The result is available here.

Text boxes¶

In presentations, one often has slides with mostly text. The textbox object is convenient for this, as one doesn’t need to use the mouse to create it. To create a slide where several text items appear one by one, one only needs to press F10 to create a textbox, then Shift+Ctrl+I to make a new view, F10 again for the next textbox, and so on. Finally, one moves the textboxes vertically for the most pleasing effect (Shift+Alt+Left Mouse does a constrained vertical translation, or Shift+Left Mouse in Translate mode).

Animations¶

If you save your presentation in HTML/JS format, then you can use animations for the transitions between different views of the same page.

The basic idea is very simple: To animate an Ipe object, you give it a name by setting the animate attribute in the context menu. When two consecutive views contain an object with the same animate name, then the object will be animated during the transition from the first view to the second.

For path objects, the animation will completely “morph” the object from the first view into the second. A triangle can smoothly turn into rectangle or even a circle, colors blend, opacity changes, line width grows or shrinks.

For all other objects, such as groups, text, images, or references, the animation is limited to changing the transformation matrix of the object. So the object will smoothly move from its original position to the new position, rotating and scaling along the way.

If the object is a single open path, you can set the animate name to start with draw:, for instance draw:my-blue-path. On the first view that includes the object, it will appear as if drawn, from starting point to end point. (You can do that for other path objects as well, but the resulting animation is less predictable.)

The most involved animation is to make an object (any object, be it path, group, or text) move along a given path. For this to happen, you give the object an animate name, for instance myobject. Then you draw a guide path: a second object consisting of a single open path, which you name slide:myobject or path:myobject. When entering a view that contains the object and a corresponding guide path, it will follow the guide path to its target position. With slide:, it will only translate, with path:, it will also rotate as the guide path turns. Note that it doesn’t matter if the previous view contained an object with the same animate name - the guide path animation has priority.

So you can have an object with name myobject in several consecutive views. In transitions without a guide path it will morph or transform, in transitions with guide path it will follow the guide path.

The guide path rotation is always around the center of the bounding box of the object (in its target position). You will therefore obtain the best results if you draw the path such that it ends in that point (that is, in the center of the bounding box of the object in its target position). Let the path start in the corresponding point of the initial position, and make sure that the tangent directions in the initial and final position are the same (from the object’s perspective). So, for instance, if the object itself is oriented identically in the start and final position, then the tangent directions should also be the same.

Bookmarks¶

You can set a section title and a subsection title for each page of an Ipe document. Theses titles will be shown in the bookmarks list (right-click on a toolbar to make it visible). Double-clicking a title brings you directly to its page, making navigation of long documents much easier. The titles are also exported to PDF, and are visible in the bookmarks view of PDF viewers.

You can also use the section title of a page to refer to this page in ipetoipe and iperender.

Excluding a page from the presentation¶

If you add a layer with name NOPDF to a page (it does not need to be visible in any view of the page), then the page is not included in the presentation. So while Ipe will show the page normally, viewing the document with a PDF reader (including IpePresenter) or as a HTML/JS presentation will not show that page.

Tricks with views¶

Changing symbolic values inside a view¶

Imagine you have an object that is shown in dark orange on your current page, but on one specific view you want to highlight the object in purple.

To achieve this, go to the view, and open Edit view from the Views menu. In the attribute map field, write this line:

color:darkorange=purple;

You will notice that all objects on the page that had the darkorange color now show in purple.

You can similarly map other attribute values, for instance:

color:navy=red;
color:darkorange=purple;
symbolsize:large=tiny;
pen:ultrafat=normal;
dashstyle:dotted=dashed;
symbol:mark/disk(sx)=mark/box(sx);

The attribute kinds you are allowed to modify are “pen”, “symbolsize”, “arrowsize”, “opacity”, “color”, “dashstyle”, and “symbol”. Both the original and the new attribute must be symbolic attributes defined in your style sheet.

It’s probably not a good idea to remap common attributes in your document—this may quickly become confusing. A better approach would be to create dedicated attribute values like emphasis, that map to some standard value in the stylesheet, and which you can then redefine in the views where you want to emphasize the object.

Controlling the PDF bounding box of a view¶

Note that all views of a page receive the same bounding box, containing all objects visible on some view, plus all objects in a layer named BBOX (even if that layer is not visible). This can be used to force a larger bounding box without adding a white rectangle or the like.

If you need independent bounding boxes for each view, create a layer named VIEWBBOX. Any view in which this layer is visible will receive a bounding box computed for the objects visible in this view only.

Making your own presentation style sheet¶

Instead of adding a presentation style sheet from Ipe, you can also create a new presentation from the command line by starting Ipe like this:

ipe -sheet presentation

Let’s have a look inside this presentation stylesheet, in case you want to roll your own.

The style sheet enlarges all standard sizes by a factor 2.8. Note the use of the <textstretch> element to magnify text:

<textstretch name="normal" value="2.8"/>
<textstretch name="large" value="2.8"/>

The text size you choose from the Ipe user interface (large, for instance) is in fact used for two symbolic attributes, namely textsize (where large maps to \large) and textstretch (where it maps to no stretch in the standard style sheet). By setting the text stretch, you can magnify fonts.

The <layout> element in this stylesheet redefines the paper size to be of the correct proportions for a projector, and defines the frame.

The <titlestyle> element defines the style of the page title, typically outside the frame.

The LaTeX-preamble defined in the <preamble> element redefines the standard font shape to cmss (Computer Modern Sans Serif). Many people find sans-serif fonts easier to read on a screen. In addition, it redefines the list environments to use less spacing, and the text styles to not justify paragraphs (the <textstyle> elements).

If you want to number the pages of the presentation, you’ll need to use the <pagenumberstyle> element. It defines color, size, position, and alignment of the page number, and provides a template for the page number text. The template can use the following Latex counters:

ipePage for the current page number,
ipeView for the current view number,
ipePages for the total number of pages,
ipeViews for the number of views of the current page,

and the special macro \ipeNumber{x}{y} that evaluates to x when the page has only one view, and to y if there is more than one view.

If the template is empty, this has the same effect as the following definition (this is also the default definition):

\ipeNumber{\arabic{ipePage}}{\arabic{ipePage} - \arabic{ipeView}}

The following example definition indicates the views of a single page with letters A, B, C, …:

<pagenumberstyle pos="300 100" size="Huge" color="navy"
halign="center">\ipeNumber{\arabic{ipePage}}{\arabic{ipePage}
\Alph{ipeView}}</pagenumberstyle>

The following definition uses roman numerals for the pages and does not indicate different views at all:

<pagenumberstyle pos="580 20" size="Huge" color="purple"
halign="right">\roman{ipePage}</pagenumberstyle>

And this shows both the current page and the total number of pages:

<pagenumberstyle pos="20 820" size="Huge" color="0.5 0 0"
valign="top">\arabic{ipePage}/\arabic{ipePages}</pagenumberstyle>

Gradient patterns¶

Gradient patterns allow to shade objects with continuously changing colors. This is often used for backgrounds, or to achieve the illusion of three-dimensional spheres or cylinders.

The intended use of gradients is to allow the creation of attractive symbols inside the style sheet, for backgrounds, as bullets in item lists (see next section), or simply to define attractive glassy-ball symbols and the like that can be used through the Use symbol ipelet.

The Ipe user interface does not offer any way of creating or editing gradients. If your stylesheet defines a gradient, then it is possible to fill a path object with this gradient, but getting the gradient coordinate system right is not trivial. (The trick is to draw the path object at gradient coordinates, and translate/rotate it to the final location afterwards.)

The definition of a linear (axial) gradient looks like this:

<gradient name="linear" type="axial" extend="yes" coords="75 0 325 0">
  <stop offset="0.05" color="1 0.4 0"/>
  <stop offset="0.95" color="1 1 0.4"/>
</gradient>

If used like this:

<path stroke="0" fill="1" gradient="linear" pen="3">
  50 50 m 350 50 l 350 150 l 50 150 l h
</path>

it will look like this:

A radial gradient looks like this:

<gradient name="radial" type="radial" extend="yes"
          coords="200 100 0 200 100 150">
  <stop offset="0" color="1 0 0"/>
  <stop offset="0.5" color="0 0 1"/>
  <stop offset="1" color="1 0 0"/>
</gradient>

It will look like this:

A common use of radial gradients is to define glassy balls like this:

<gradient name="ball" type="radial" coords="-4 10 2 0 0 18">
  <stop offset="0" color="1 1 1"/>
  <stop offset="1" color="0 0 1"/>
</gradient>

Note that the gradient is centered at 0 0, so it needs to be moved to the location where it is used:

<path matrix="3 0 0 3 100 100" fill="1" gradient="ball">
  18 0 0 18 0 0 e
</path>

Normally, you would define a symbol looking like a glassy ball in your style sheet:

<ipestyle>
  <gradient name="ball" type="radial" coords="-4 10 2 0 0 18">
    <stop offset="0" color="1 1 1"/>
    <stop offset="1" color="0 0 1"/>
  </gradient>
  <symbol name="ball(x)" transformations="translations">
    <path fill="1" gradient="ball"> 18 0 0 18 0 0 e </path>
  </symbol>
</ipestyle>

The glassy ball can then be used in the document using the Use symbol ipelet. Note that transformations="translations" ensures that stretching your drawing does not change the glassy ball. Adding the (x) suffix to the symbol name allows you to resize the glassy ball by changing the symbol size from the properties (the same selector used to change the mark size).

For the precise syntax of the gradient definition see here. The easiest method of creating gradients, though, is to use an SVG editor such as Inkscape and to convert the SVG gradient to Ipe format using svgtoipe.

Prettier bullet points¶

Presentations often make use of itemize environments. You can make these prettier in a number of ways:

You can color your bullets:

<preamble>
\def\labelitemi{\LARGE\textcolor{red}{$\bullet$}}
</preamble>

Enumeration numbers could be put in a colored box:

<preamble>
\newcommand{\labelenumi}{\fbox{\Roman{enumi}}}
</preamble>

You could use the Dingbats font for nice enumerations, for instance by putting \usepackage{pifont} in your preamble, and then having text objects with \begin{dinglist}{43} or \begin{dingautolist}{172} (or use 182, 192, 202 for various circled numbers).

You can mark items as good and bad using these “bullets”:

Bad item: \textcolor{red}{\ding{55}}

Good item: \textcolor{green}{\ding{52}}

Filming from the canvas¶

Some Ipe users make presentation videos directly from Ipe, as follows:

Make Ipe full-screen (Zoom menu);
Turn off the grid (Zoom menu);
Enable pretty display (Zoom menu);
Mac: Turn off the Snap toolbar and possibly the mode toolbar (Zoom menu);
Linux: Turn off or rearrange toolbars and panels to taste;
Windows: Turn off or rearrange toolbars by setting prefs.win_toolbar_order;
Set up your video software to film the canvas area of Ipe (where your document is shown).

You can now go through your presentation, using the Laser pointer mode to point to items on your slide, and using ink mode to write annotations directly onto the slides.

For this to work well, it is essential that the width of the canvas remains fixed while you step through your document. Try it before you start filming! You can change the contents of the “View” and “Page” buttons by changing the preferences prefs.view_button_prefix and prefs.page_button_prefix. Furthermore, on MacOS, you can force the canvas width to remain fixed by making prefs.osx_properties_width large enough.