[Tex/LaTex] Beamer boxes with flat shadows

beamershadowstikz-pgf

Is there a possibility to change the 'faded out' shadows from beamer boxes to 'flat shadows'?

With flat shadow I am referring to a shadow of a single color without a gradient. Ideally, I would like to have an opaque drop shadow in the style of the tikz.shadows library. It can be used as follows to add a flat shadow to a node:

 \node[draw,drop shadow={opacity=.25, shadow xshift=0.07, shadow yshift=-0.07, color=green}] at (0,0) {node with green shadow};

This is my MWE beamer document containing a single box with a fading shadow:

\documentclass{beamer}

\setbeamertemplate{blocks}[rounded][shadow=true] % use rounded blocks with standard beamer shadow

\begin{document}
\begin{frame}{Example frame}
  \begin{block}{Block with shadow}
    I, box, have a gradient shadow but I want a flat shadow.
  \end{block}
\end{frame}
\end{document}

The definition of the box shadows is most certainly contained in beamerbasedboxes.sty of the beamer package. Unfortunately, I do not understand the code since it mostly uses low level pgf commands instead of tikz commands. So far, I have tried to modify several commands in this file, but without success. Or maybe I have simply overlooked an option of the blocks template?

Best Answer

While someone provides a only-beamer-solution, you could consider to use tcolorbox and its easily customizable boxes.

\documentclass{beamer}

\usepackage[most]{tcolorbox}

\setbeamertemplate{blocks}[rounded][shadow=true] % use rounded blocks with standard beamer shadow

\begin{document}
\begin{frame}{Example frame}
  \begin{block}{Block with shadow}
    I, box, have a gradient shadow but I want a flat shadow.
  \end{block}

\begin{tcolorbox}[enhanced,drop shadow, title=Example with tcolorbox]
    I, box, have a flat shadow.
\end{tcolorbox}  

\end{frame}
\end{document}

2nd version:

Although I'm don't know what I did, after some tests I've got

from:

\documentclass{beamer}

\setbeamertemplate{blocks}[rounded][shadow=true] % use rounded blocks with standard beamer shadow

\makeatletter
\pgfdeclareradialshading[black,bg]{bmb@shadowball}{\pgfpointorigin}{%
  color(0bp)=(black!20!bg); color(4bp)=(black!20!bg)}
\pgfdeclareradialshading[black,bg]{bmb@shadowballlarge}{\pgfpointorigin}{%
  color(0bp)=(black!20!bg); color(4bp)=(black!20!bg); color(8bp)=(black!20!bg)}\pgfdeclareverticalshading[black,bg]{bmb@shadow}{200cm}{%
  color(0bp)=(black!20!bg); color(4bp)=(black!20!bg); color(6bp)=(black!20!bg)}
\makeatother

\begin{document}
\begin{frame}{Example frame}
  \begin{block}{Block with shadow}
    I, box, have a gradient shadow but I want a flat shadow.
  \end{block}  

\end{frame}
\end{document}

Related Solutions

[Tex/LaTex] Beamerposter: rounded and shadowed blocks

I stumbled in a similar problem and solved it with the tcolorbox package. Here is the code:

\documentclass[final]{beamer}
\usepackage[orientation=portrait,size=a0,scale=1.4,debug]{beamerposter}     
\usepackage{tcolorbox}                                 %
\tcbuselibrary{skins}                                  %  preamble 
\usepackage{tikz}                                      %
\usetikzlibrary{shadows,shadings}                      %

\tikzset{myshadow/.style={                             % custom shadow with tikz
         opacity=.85,
         shadow xshift=0.15,
         shadow yshift=-0.15,
         shade,
         shading=axis,
         shading angle=230}
         } 
\tcbset{                                               % set a custom tcolorbox  
        skin=enhanced,                                 % enables use of shadows
        frame style={fill=gray,drop shadow={myshadow}}, % sets the frame color and the shadow properties
        bottom=7mm,                                    % distance between the body text and the bottom frame
        top=14mm,                                      % distance between the body text and the top frame
        boxrule=0mm,                                   % frame width
        bottomtitle=5mm,                               % distance between the title text and the bottom title frame               
        toptitle=5mm,                                  % distance between the title text and the top title frame
        lefttitle=1cm                                  % title text left margin
}  
\begin{document}
\begin{frame}  
\begin{columns}
\begin{column}{.3\textwidth}
\begin{tcolorbox}[title=\large Fontsizes]
 \centering
  {\tiny tiny}\par
  {\scriptsize scriptsize}\par
  {\footnotesize footnotesize}\par
  {\normalsize normalsize}\par
\end{tcolorbox}
\end{column}
\end{columns}
\end{frame}
\end{document}

the result is this:
enter image description here
for comparison:

I tried to explain everything in the code. If you want all the tcolorboxes to be like this, just put the \tcbset code in the preamble, otherwise start a group just before the tcolorboxes you want to customize in that way.

The only thing that doesn't really look the same is the shadow (my shadow isn't blurred), but with some tweaks and the shadows.blur tikzlibrary it should be possible to obtain the exact same result.

TikZ-PGF – Removing Drop Shadow from One Node

You can kill the general shadow key with general shadows/.style= and use this on the child, i.e.:

% Preamble:
\tikzset{no shadows/.style={general shadow/.style=}}

% In the tree:
  child[no shadows] {node {Winesap}}

which would disable all shadows on that child.

Another option is to empty the macro that stores the preactions, something like

% Preamble:
\makeatletter
\tikzset{no shadows/.code=\let\tikz@preactions\pgfutil@empty}
\makeatother

% In the tree:
  child {node[no shadows] {Winesap}}

which would kill all possible preactions but would only affect this node.

Code A

\documentclass{beamer}
\usecolortheme[named=teal]{structure}
\usepackage{tikz}
\usetikzlibrary{shadows,trees}
\tikzset{
  edge from parent fork right,
  grow'=right,
  every node/.style={rectangle,rounded corners,thick,draw=structure,fill=white,drop shadow},
  edge from parent/.style={thick,draw=structure},
  no shadows/.style={general shadow/.style=},
}
\begin{document}
\begin{frame}
\begin{tikzpicture}[
  level 1/.style={level distance=7em,sibling distance=9em},
  level 2/.style={level distance=7em,sibling distance=6em},
  level 3/.style={level distance=7em,sibling distance=3em}]
\node {food}
  child {node {fruit}
    child {node {apples}
      child {node {Granny Smith}}
      child[no shadows] {node {Winesap}}
    }
    child {node {pears}}
  }
  child {node {veggies}
    child {node {beets}}
    child {node {Swiss chard}}
  };
\end{tikzpicture}
\end{frame}
\end{document}

Code B

\documentclass{beamer}
\usecolortheme[named=teal]{structure}
\usepackage{tikz}
\usetikzlibrary{shadows,trees}
\makeatletter
\tikzset{no shadows/.code=\let\tikz@preactions\pgfutil@empty}
\makeatother
\tikzset{
  edge from parent fork right,
  grow'=right,
  every node/.style={rectangle,rounded corners,thick,draw=structure,fill=white,drop shadow},
  edge from parent/.style={thick,draw=structure},
}
\begin{document}
\begin{frame}
\begin{tikzpicture}[
  level 1/.style={level distance=7em,sibling distance=9em},
  level 2/.style={level distance=7em,sibling distance=6em},
  level 3/.style={level distance=7em,sibling distance=3em}]
\node {food}
  child {node {fruit}
    child {node {apples}
      child {node {Granny Smith}}
      child {node[no shadows] {Winesap}}
    }
    child {node {pears}}
  }
  child {node {veggies}
    child {node {beets}}
    child {node {Swiss chard}}
  };
\end{tikzpicture}
\end{frame}
\end{document}