A beamer fade out-fade in effect?

2,743

Some points:

  • You can use \usebackgroundtemplate and pdfpages to insert slides as background.
  • to indicate the pervious slide, \beamer@startpageofframe is useful.
  • use mdframed and tikz to block the pervious slide.
  • Since it is dangerous to insert a pdf into itself, I created two files 199832-main.tex and 199832-material.pdf. They are almost identical except that in 199832-material.pdf the line begins with \usebackgroundtemplate is commented out.

So the 10th pages are as follows:

Here is the code

\documentclass[t]{beamer}
\usetheme{Berkeley}
\beamertemplatenavigationsymbolsempty

\usepackage{pdfpages}
\usepackage[hidealllines=true,backgroundcolor=white,framemethod=tikz]{mdframed}
\newmdenv[settings={\tikzset{every picture/.style={opacity=0.95}}}]{mymdframed}

\begin{document}

    \begin{frame}\begin{mymdframed}
        \only<+->{AAAAAAAA AAAAAAAA AAAAAAAA AAAAAAAA \\ AAAAAAAA AAAAAAAA AAAAAAAA AAAAAAAA \\}
        \only<+->{AAAAAAAA AAAAAAAA AAAAAAAA AAAAAAAA \\ AAAAAAAA AAAAAAAA AAAAAAAA AAAAAAAA \\}
        \only<+->{AAAAAAAA AAAAAAAA AAAAAAAA AAAAAAAA \\ AAAAAAAA AAAAAAAA AAAAAAAA AAAAAAAA \\}
        \only<+->{AAAAAAAA AAAAAAAA AAAAAAAA AAAAAAAA \\ AAAAAAAA AAAAAAAA AAAAAAAA AAAAAAAA \\}
    \end{mymdframed}\end{frame}

\makeatletter
\newcount\my@frameendprev
\usebackgroundtemplate{\vbox{\my@frameendprev\beamer@startpageofframe\advance\my@frameendprev by-1\includepdf[pages={\the\my@frameendprev}]{199832-material.pdf}}}
\makeatother

    \begin{frame}\begin{mymdframed}
        \only<+->{BBBBBBBB BBBBBBBB BBBBBBBB BBBBBBBB \\ BBBBBBBB BBBBBBBB BBBBBBBB BBBBBBBB \\}
        \only<+->{BBBBBBBB BBBBBBBB BBBBBBBB BBBBBBBB \\ BBBBBBBB BBBBBBBB BBBBBBBB BBBBBBBB \\}
        \only<+->{BBBBBBBB BBBBBBBB BBBBBBBB BBBBBBBB \\ BBBBBBBB BBBBBBBB BBBBBBBB BBBBBBBB \\}
        \only<+->{BBBBBBBB BBBBBBBB BBBBBBBB BBBBBBBB \\ BBBBBBBB BBBBBBBB BBBBBBBB BBBBBBBB \\}
    \end{mymdframed}\end{frame}

    \begin{frame}\begin{mymdframed}
        \only<+->{CCCCCCCC CCCCCCCC CCCCCCCC CCCCCCCC \\ CCCCCCCC CCCCCCCC CCCCCCCC CCCCCCCC \\}
        \only<+->{CCCCCCCC CCCCCCCC CCCCCCCC CCCCCCCC \\ CCCCCCCC CCCCCCCC CCCCCCCC CCCCCCCC \\}
        \only<+->{CCCCCCCC CCCCCCCC CCCCCCCC CCCCCCCC \\ CCCCCCCC CCCCCCCC CCCCCCCC CCCCCCCC \\}
        \only<+->{CCCCCCCC CCCCCCCC CCCCCCCC CCCCCCCC \\ CCCCCCCC CCCCCCCC CCCCCCCC CCCCCCCC \\}
    \end{mymdframed}\end{frame}

    \begin{frame}\begin{mymdframed}
        \only<+->{DDDDDDDD DDDDDDDD DDDDDDDD DDDDDDDD \\ DDDDDDDD DDDDDDDD DDDDDDDD DDDDDDDD \\}
        \only<+->{DDDDDDDD DDDDDDDD DDDDDDDD DDDDDDDD \\ DDDDDDDD DDDDDDDD DDDDDDDD DDDDDDDD \\}
        \only<+->{DDDDDDDD DDDDDDDD DDDDDDDD DDDDDDDD \\ DDDDDDDD DDDDDDDD DDDDDDDD DDDDDDDD \\}
        \only<+->{DDDDDDDD DDDDDDDD DDDDDDDD DDDDDDDD \\ DDDDDDDD DDDDDDDD DDDDDDDD DDDDDDDD \\}
    \end{mymdframed}\end{frame}

\end{document}
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Xi'an
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Xi'an

Updated on January 02, 2021

Comments

  • Xi'an
    Xi'an almost 3 years

    In some of my slides, especially the technical ones, I would like to keep the bottom of the previous slide, preferably somewhat faded, as the bottom top of the next slide as I start introducing new material so that readers could keep in sight the flow of ideas and notations. In a sense, like when one writes on the blackboard. Ànd erases one line at a time...

    For instance, something like an automated version of the following...

    \documentclass[xcolor=dvipsnames,professionalfonts]{beamer}
    \usepackage{xcolor}
    \begin{document}
    \begin{frame}
    This is an important theorem due to Euler:
    
    \pause
    \bigskip
    \begin{block}{Theorem}
    If $n$ and $a$ are coprime positive integers, then
    $$
        a^{\varphi (n)} \equiv 1 \pmod{n}
    $$
    where $\varphi(n)$ is Euler's totient function
    \end{block}
    \end{frame}
    \begin{frame}
    There is a direct proof: Let $R = \{x_1, x_2, ..., x_{\varphi(n)}\}$ be a reduced residue system
    (mod $n$) and let $a$ be any integer coprime to $n$. The proof hinges on the fundamental fact that
    multiplication by $a$ permutes the $x_i$:
    
    \only<1>{
    \textcolor{lightgray}{\begin{block}{Theorem}
    \textcolor{lightgray}{If $n$ and $a$ are coprime positive integers, then
    $$
        a^{\varphi (n)} \equiv 1 \pmod{n}
    $$
    where $\varphi(n)$ is Euler's totient function}
    \end{block}}}
    \only<2>{
    in other words if $ax_j ≡ ax_k (\pmod n)$ then $j = k$. That is, the sets $R$ and $aR = \{ax_1, ax_2, ..., ax_{\varpi(n)}\}$,
    considered as sets of congruence classes $(\pmod n)$, are identical
    so the product of all the numbers in $R$ is congruent $(\pmod n)$ to the product of all the numbers in $aR$:
    $$
        \prod_{i=1}^{\varphi(n)} x_i \equiv \prod_{i=1}^{\varphi(n)}
        ax_i \equiv a^{\varphi(n)}\prod_{i=1}^{\varphi(n)} x_i \pmod{n},
    $$
    and using the cancellation law to cancel the $x_i$'s gives Euler's theorem:
    $$
        a^{\varphi(n)}\equiv 1 \pmod{n}.
    $$}
    \end{frame}
    \end{document}
    
    • Johannes_B
      Johannes_B about 9 years
      Do you just mean something as simple as \pause or more complex thing? Like temporal
    • Old Nick
      Old Nick about 9 years
      I think you can achieve the desired effect with the beamer overlays specs but a possible solution would be relative to the actual content of your slide, so you need to post a minimal working example (MWE) to work with. Anyway, welcome to TeX.SX!