You could use the pgf-blur package, which gives you this:
In fact, it can add a "faded" drop shadow to pretty much anything:
The shadow fading is not continuous, like in the previously accepted answer. It fades in a number of discrete steps, but that number can be changed, see the documentation.
Here's the code for the examples:
\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{shadows.blur}
\usetikzlibrary{shapes.symbols}
\begin{document}
\begin{center}
\begin{tikzpicture}
\node[draw=none,shade,
top color=blue!40,
bottom color=blue!5,
rounded corners=6pt,
blur shadow={shadow blur steps=5}
] {\sffamily\bfseries\large A pretty box};
\node[tape,draw=none,shade,
top color=blue!40,
bottom color=blue!5,
rounded corners=1pt,
blur shadow={shadow blur steps=5,shadow blur extra rounding=1.3pt}
] at (5,0){\sffamily\bfseries\large Another pretty box};
\end{tikzpicture}
\end{center}
\end{document}
Edit
Sometimes, PDF renderers will show a dark line in the center of the shadow. This is due to the way they handle anti-aliasing and clipping. To avoid this:
- Use pgf-blur v1.01, which tries hard to hide this artefact
- In Acrobat, turn off the "Page Display" preference "Enhance thin lines". These shadows consist of many thin lines, and they won't look good if Acrobat changes their width
- Don't use too many
blur shadow steps. It looks best if you have about two pixels per step at viewing resolution.
One option using singleextra, firstextra to place the title, instead of frametitle; in this way you can easily obtain the desired shading effect for the background. To control the shadow attributes, you can use all the available keys for example scale, xshift, yshift (refer to the PGF manual). For frames without page breaks a decoration was added midways vertically on the right side (as requested in a comment):
\documentclass{article}
\usepackage[a6paper]{geometry}% just for the example
\usepackage[framemethod=tikz]{mdframed}
\usepackage{amsmath,amssymb}
\usetikzlibrary{calc}
\usetikzlibrary{shadows.blur}
\usetikzlibrary{shapes.symbols}
\usetikzlibrary{shadows}
\newcounter{exe}
\newenvironment{Fancybox}[1][\textwidth]
{\stepcounter{exe}%
\mdfsetup{
singleextra={%
\node[draw=blue!40,anchor=east,rectangle, thick,font=\color{black}, double,
top color=blue!40,
bottom color=blue!5,
rounded corners=8pt,
drop shadow={shadow xshift=1.5pt, shadow yshift=-1.5pt},anchor=west
] at ([xshift=20pt]O|-P)
{\strut Example~\theexe};
\path let \p1=(P), \p2=(O) in node[fill=blue!40,font=\color{white}] at (P|-0,0.5*\y2+0.5*\y1) {$\clubsuit$};},%
firstextra={%
\node[draw=blue!40,anchor=east,rectangle, thick,font=\color{black}, double,
top color=blue!40,
bottom color=blue!5,
rounded corners=8pt,
drop shadow={shadow xshift=1.5pt, shadow yshift=-1.5pt},anchor=west
] at ([xshift=20pt]O|-P)
{\strut Example~\theexe};},%
skipabove=\topskip,
skipbelow=\topskip,
innertopmargin=18pt,
linecolor=red,%
innerlinewidth=0.8pt,
topline=true,
apptotikzsetting={\tikzset{mdfbackground/.append style={%
shade,top color=blue!35, bottom color=white}}},
frametitleaboveskip=\dimexpr-\ht\strutbox\relax,
roundcorner=5pt,
linecolor=blue,%
innerlinewidth=1pt,
topline=true,
shadow=true,
rightline=true,innerleftmargin=10,innerrightmargin=10,
shadowcolor=blue!40,
}
\begin{mdframed}[userdefinedwidth=#1]\relax%
}
{\end{mdframed}}
\begin{document}
\begin{Fancybox}
To calculate the horizontal position the kinematic differential
equations are needed:
\begin{align}
\dot{n} &= u\cos\psi -v\sin\psi \\
\dot{e} &= u\sin\psi + v\cos\psi
\end{align}
For small angles the following approximation can be used:
\begin{align}
\dot{n} &= u -v\delta_\psi \\
\dot{e} &= u\delta_\psi + v
\end{align}
\end{Fancybox}
\begin{Fancybox}
To calculate the horizontal position the kinematic differential
equations are needed:
\begin{align}
\dot{n} &= u\cos\psi -v\sin\psi \\
\dot{e} &= u\sin\psi + v\cos\psi
\end{align}
For small angles the following approximation can be used:
\begin{align}
\dot{n} &= u -v\delta_\psi \\
\dot{e} &= u\delta_\psi + v
\end{align}
For small angles the following approximation can be used:
\begin{align}
\dot{n} &= u -v\delta_\psi \\
\dot{e} &= u\delta_\psi + v
\end{align}
\end{Fancybox}
\begin{Fancybox}[7cm]
To calculate the horizontal position the kinematic differential equations are needed:
\begin{align}
\dot{n} &= u -v\delta_\psi \\
\dot{e} &= u\delta_\psi + v
\end{align}
\end{Fancybox}
\end{document}
Best Answer
Completely EDIT 2012-03-04:
I uploaded the new version 1.3 to CTAN. At the moment the files are available at github.
This version provides a key named
shadow. This allows to draw a shadow. The shadow can be manipulated by the new keysshadowsizeandshadowcolorIf you use
framemethod=tikzit is important to load the TikZ libraryshadows.mdframedcan do the job but I don't want to load any libraries.For the methods TikZ and PSTricks I defined a style
mdfshadowbytikzset/newpsstyle. For more settings manipulate this key.Based of the new modification I created the following example:
The result is:
An other example is provided in file
mdframed-example-pstricks.pdfwhich usespstricksandframetitle: