Beamer: Create box with 'sunken' shadow

Question

I'm currently using the block environment of the beamer class and I wondered whether it is possible to have some kind of 'sunken' shadow.

According to the documentation you can only choose between turning on or off shadows.

It would be really nice for visualizing that something belongs to a 'lower' level similar to box with 'sunken' shadow http://www.html5code.nl/wp-content/uploads/css3_box_shadow8.png

Answer 1

You could fake something similar to your image

\documentclass{beamer}
\usetheme{CambridgeUS} 

\usepackage[most]{tcolorbox}  

\newenvironment{emblock}
  {\begin{actionenv}\begin{tcolorbox}[
                    enhanced,
            colframe=white,
            colback=white, 
                    borderline north={0.2mm}{0.6mm}{gray!25!white},
                    borderline west ={0.2mm}{0.6mm}{gray!25!white},
                    borderline north={0.2mm}{0.4mm}{gray!50!white},
                    borderline west ={0.2mm}{0.4mm}{gray!50!white},
                    borderline south ={0.2mm}{0.0mm}{gray!50!white},
                    borderline east ={0.2mm}{0.0mm}{gray!50!white},
                    borderline north={0.2mm}{0.2mm}{gray!75!white},
                    borderline west ={0.2mm}{0.2mm}{gray!75!white},
                    borderline north={0.2mm}{0.0mm}{gray},
                    borderline west ={0.2mm}{0.0mm}{gray},
    ]
  }
  {\end{tcolorbox}\end{actionenv}}

\newenvironment{hblock}
  {\begin{actionenv}\begin{tcolorbox}[
                    enhanced,
            colframe=white,
            colback=white, 
                    borderline south={0.2mm}{0.6mm}{gray},
                    borderline east ={0.2mm}{0.6mm}{gray},
                    borderline south={0.2mm}{0.4mm}{gray!75!white},
                    borderline east ={0.2mm}{0.4mm}{gray!75!white},             
                    borderline south={0.2mm}{0.2mm}{gray!50!white},
                    borderline east ={0.2mm}{0.2mm}{gray!50!white},
                    borderline north={0.2mm}{0.0mm}{gray!50!white},
                    borderline west ={0.2mm}{0.0mm}{gray!50!white},
                    borderline south={0.2mm}{0.0mm}{gray!25!white},
                    borderline east ={0.2mm}{0.0mm}{gray!25!white},
    ]
  }
  {\end{tcolorbox}\end{actionenv}}

\begin{document}
    \begin{frame} 
        \begin{emblock} 
            Preface 
            \end{emblock} 

        \begin{hblock} 
            Preface 
            \end{hblock}            
    \end{frame} 
\end{document}

Answer 2

Perhaps something like this:

\documentclass{beamer}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{tikz}
\usetikzlibrary{calc}
\usetikzlibrary{fadings}
\usetikzlibrary{backgrounds}

\definecolor{consolegray}{RGB}{192,192,192}
\newcommand\cfwidth{5pt}
\begin{document}
\begin{frame}
\begin{tikzpicture}
\node[inner sep=1em,
      line width=\cfwidth,
      draw=consolegray,
      fill=black,
      text=consolegray] (error) 
 {\ttfamily\footnotesize\begin{tabular}{@{}l@{}}
! LaTeX Error: Something's wrong--perhaps a missing \textbackslash item.\\\\

See the LaTeX manual or LaTeX Companion for explanation.\\
Type  H <return>  for immediate help.\\
 ...
\end{tabular}};


\shade[left color=consolegray!70!black,right color=consolegray, middle color=consolegray!10!white] (error.south west) -- (error.north west) --
            ($(error.north west)+(\cfwidth,-\cfwidth)$)  -- ($(error.south west)+(\cfwidth,\cfwidth)$) --cycle ;

\shade[top color=consolegray!70!black,bottom color=consolegray, middle color=consolegray!10!white] (error.north west) -- (error.north east) --
            ($(error.north east)+(-\cfwidth,-\cfwidth)$)  -- ($(error.north west)+(\cfwidth,-\cfwidth)$) --cycle ;

\shade[left color=consolegray,right color=consolegray!70!black, middle color=consolegray!10!white] (error.north east) -- (error.south east) --
            ($(error.south east)+(-\cfwidth,\cfwidth)$)  -- ($(error.north east)+(-\cfwidth,-\cfwidth)$) --cycle ;

\shade[top color=consolegray,bottom color=consolegray!70!black, middle color=consolegray!10!white] (error.south east) -- (error.south west) --
            ($(error.south west)+(\cfwidth,\cfwidth)$)  -- ($(error.south east)+(-\cfwidth,\cfwidth)$) --cycle ;

\end{tikzpicture}
\end{frame}
\end{document}

Answer 3

This could be a job for the vignette library of tcolorbox.

How about the following:

\documentclass{beamer}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[vignette,skins]{tcolorbox}

\newtcolorbox{bevel}[1][]{enhanced,
  colback=white,colframe=white,
  sharp corners,boxrule=1mm,#1,
  underlay={\begin{tcbclipframe}\tcbvignette{%
    size=1mm,
    draw method=clipped,
    north style={black!80,path fading=south},
    east style={black!30,path fading=west},
    south style={black!10,path fading=north},
    west style={black!60,path fading=east},
    inside node=frame
  }\end{tcbclipframe}}}

\begin{document}
  \begin{frame}
    \begin{bevel}
      Some text.
     \end{bevel}

    \begin{bevel}[hbox]
      Some text.
    \end{bevel}

    \begin{bevel}[hbox,colback=blue!20,colframe=blue!30]
      Some text.
    \end{bevel}

  \end{frame}
\end{document}