This MWE code is adapted from this example on www.texample.net and was originally written by SE user cfr:
\documentclass{article}
\usepackage{graphicx}
\usepackage{tikz}
\usetikzlibrary{arrows.meta, shapes.geometric, calc, shadows}
\usepackage{forest}
\usepackage{adjustbox}
\colorlet{mygreen}{green!75!black}
\colorlet{col1in}{red!30}
\colorlet{col1out}{red!40}
\colorlet{col2in}{mygreen!40}
\colorlet{col2out}{mygreen!50}
\colorlet{col3in}{blue!30}
\colorlet{col3out}{blue!40}
\colorlet{col4in}{mygreen!20}
\colorlet{col4out}{mygreen!30}
\colorlet{col5in}{blue!10}
\colorlet{col5out}{blue!20}
\colorlet{col6in}{blue!20}
\colorlet{col6out}{blue!30}
\colorlet{col7out}{orange}
\colorlet{col7in}{orange!50}
\colorlet{col8out}{orange!40}
\colorlet{col8in}{orange!20}
\colorlet{linecol}{blue!60}
\begin{document}
\tikzset{
basic/.style = {draw, drop shadow, rectangle},
root/.style = {basic, rounded corners=2pt, thin, align=center,
fill=green!30},
level 2/.style = {basic, rounded corners=6pt, thin,align=center, fill=blue!10},
level 3/.style = {basic, thin, align=left, fill=green!10}
}
\pgfkeys{/forest,
rect/.append style = {rectangle, rounded corners = 2pt,
inner color = col6in, outer color = col6out},
ellip/.append style = {ellipse, inner color = col5in,
outer color = col5out},
orect/.append style = {rect, font = \sffamily\bfseries\LARGE,
text width = 325pt, text centered,
minimum height = 10pt, outer color = col7out,
inner color=col7in},
oellip/.append style = {ellip, inner color = col8in, outer color = col8out,
font = \sffamily\bfseries\large, text centered}}
\begin{figure}[h]
\begin{adjustbox}{max width=1.2\textwidth,center}
\begin{forest}
for tree={
font=\sffamily\bfseries,
line width=1pt,
draw=linecol,
ellip,
align=center,
child anchor=north,
parent anchor=south,
drop shadow,
l sep+=12.5pt,
edge path={
\noexpand\path[color=linecol, rounded corners=5pt,
>={Stealth[length=10pt]}, line width=1pt, ->, \forestoption{edge}]
(!u.parent anchor) -- +(0,-5pt) -|
(.child anchor)\forestoption{edge label};
},
where level={3}{tier=tier3}{},
where level={0}{l sep-=15pt}{},
where level={1}{
if n={1}{
edge path={
\noexpand\path[color=linecol, rounded corners=5pt,
>={Stealth[length=10pt]}, line width=1pt, ->,
\forestoption{edge}]
(!u.west) -| (.child anchor)\forestoption{edge label};
},
}{
edge path={
\noexpand\path[color=linecol, rounded corners=5pt,
>={Stealth[length=10pt]}, line width=1pt, ->,
\forestoption{edge}]
(!u.east) -| (.child anchor)\forestoption{edge label};
},
}
}{},
}
[\Huge Total drag, yshift = 3cm, inner color=col1in, outer color=col1out
[\huge Viscous drag, yshift = 1cm, inner color=col2in, outer color=col2out
[\Large Displacement separation, inner color=col4in, outer color=col4out
]
[\Large Boundary layer shear, inner color=col4in, outer color=col4out
]
]
[\huge Vortex drag, yshift = 1cm, inner color=col3in, outer color=col3out
[\Large Trailing vortices due to lift
]
]
[\huge Wave drag, yshift = 1cm, inner color=col3in, outer color=col3out
[\Large Waves due to lift
]
[\Large Waves due to volume
]
]
]
]
\end{forest}
\end{adjustbox}
\end{figure}
\end{document}
produces this:
How can I add a large horizontal curly brace do add a comment to all the bottom nodes, to get something like this:
