Overlays

Probably the most interesting effect achieved by Prosper is overlays, which gives the appearance of incremental exposure of a given slide. Prosper provides two different mechanisms for achieving this. The first, and the easier one to describe, allows incremental exposure of an itemized list. The second, which is a bit more complicated, allows incremental exposure of any part of a slide, not necessarily contained in an itemized list.

Overlays with itemized lists

Prosper defines a new LaTeX environment, called itemstep, which can be used to expose an itemized list one item at a time. The following sample LaTeX file illustrates the concept:

% overlays1.tex
\documentclass[pdf,umbc4,slideColor,colorBG]{prosper}
\begin{document}

\overlays{5}{%
\begin{slide}{Outline of the talk}

\begin{itemstep}
	\item Introduction
	\item Statement of the main theorem
	\item Technical lemmata
	\item Proof of the main theorem
	\item Conclusions
\end{itemstep}

\end{slide}
}  % closing brace of \overlays

\end{document}

When this file is compiled into the PDF format and displayed with a PDF viewer, such as the Acrobat Reader, the items are exposed one-at-a-time as you page forward through the document in the usual way. The fully exposed slide looks like this:

Overlays in general

The following sample input illustrates how to expose a slide incrementally. I think the syntax is obvious.

% overlays2.tex
\documentclass[pdf,rico,slideColor,colorBG]{prosper}
\begin{document}

\overlays{3}{%
\begin{slide}{Fermat's Last Theorem}

In this talk I will give a very elementary proof of the
theorem.  I am surprised that no one else has thought of
this before.

\medskip

\fromSlide{2}{%
Fermat's Last Theorem says that the equation
\[
        x^2 + y^2 = z^2
\]
has no solution in the set of natural numbers.
} % closing brace of \fromSlide

\medskip

\fromSlide{3}{%
This is not true.  After a lengthy calculation on the
department's Linux machines, I have verified that within
the numerical accuracy of the Pentium-4 processor, we have:
\[
        5000^2 + 12000^2 = 13000^2
\]
} % closing brace of \fromSlide

\end{slide}
}  % closing brace of \overlays

\end{document}

A PDF viewer will expose the resulting file one paragraph at a time. The fully exposed slide looks like this:

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