13

I need to be able to do this kind of highlighting (or glow) on different figures like vectors, lines, circles, arcs, but I have no idea how to do it, this is a code example

\documentclass[,varwidth,border=1pt]{standalone}
\usepackage[dvipsnames,svgnames,x11names,]{xcolor}
\usepackage{pgf,tikz,tikz-3dplot}
%
\begin{document}
%
\begin{tikzpicture}[ >=latex]
\draw[->] (-4,0)--(5,0) node[at end,above]{$x$};
\draw[->] (0,-1,0)--(0,5,0) node[at end,right]{$y$};
\draw[->] (0,0) coordinate(O) -- ({5*cos(30)},{5*sin(30)}) coordinate (XP)  node[pos=1.1]{$x'$};
\draw[->] (O) -- ({-5*sin(30)},{5*cos(30)}) coordinate (YP) node[pos=1.1]{$y'$};
\draw[->, red] (O) -- ({4*cos(50)}, {4*sin(50)}) coordinate(R);
\draw[blue] (R)|-coordinate (Q) (O);
\draw[green] (O) -- ({4*cos(50)*cos(30)*cos(30)}, {4*cos(50)*cos(30)*sin(30)})-- (Q);
\draw[<->, Orchid] (1.25,0) arc (0:30:1.25cm) node[midway, right ]{$\theta_{11}$};
\draw[<->, Firebrick2] (30:1.25) arc (30:50:1.25cm) node[midway, right ]{$\theta_{12}$};
\draw[yellow] (Q)--++({ 4*sin(50)*sin(30)*cos(30) }, { 4*sin(50)*sin(30)*sin(30) } )-- (R);
\end{tikzpicture}
%
\end{document}

this is an example of "this glow"

TIKZ vs GLOWIMAGE

Thanks for the help!!

2
  • @mabartibin: It would be wonderful, if blur shadow had a color option, so it could be used for things like this. Nov 4 '20 at 22:33
  • yes, It would be!!! Nov 5 '20 at 1:01
15

I made a glow style, that simply draws the line several times with increasing thickness and and low opacity. The glow can be a different color from the line. If the line has an arrow it look strange, but you can simply draw it first with glow, and the again with the arrow.

\documentclass[,varwidth,border=1pt]{standalone}
\usepackage[dvipsnames,svgnames,x11names,]{xcolor}
\usepackage{pgf,tikz,tikz-3dplot}
\tikzset{%
glow/.style={%
preaction={#1, draw, line join=round, line width=0.5pt, opacity=0.04,
preaction={#1, draw, line join=round, line width=1.0pt, opacity=0.04,
preaction={#1, draw, line join=round, line width=1.5pt, opacity=0.04,
preaction={#1, draw, line join=round, line width=2.0pt, opacity=0.04,
preaction={#1, draw, line join=round, line width=2.5pt, opacity=0.04,
preaction={#1, draw, line join=round, line width=3.0pt, opacity=0.04,
preaction={#1, draw, line join=round, line width=3.5pt, opacity=0.04,
preaction={#1, draw, line join=round, line width=4.0pt, opacity=0.04,
preaction={#1, draw, line join=round, line width=4.5pt, opacity=0.04,
preaction={#1, draw, line join=round, line width=5.0pt, opacity=0.04,
preaction={#1, draw, line join=round, line width=5.5pt, opacity=0.04,
preaction={#1, draw, line join=round, line width=6.0pt, opacity=0.04,
}}}}}}}}}}}}}}
\begin{document}
\begin{tikzpicture}[ >=latex]
\draw[->] (-4,0)--(5,0) node[at end,above]{$x$};
\draw[->] (0,-1,0)--(0,5,0) node[at end,right]{$y$};
\draw[->] (0,0) coordinate(O) -- ({5*cos(30)},{5*sin(30)}) coordinate (XP)  node[pos=1.1]{$x'$};
\draw[->] (O) -- ({-5*sin(30)},{5*cos(30)}) coordinate (YP) node[pos=1.1]{$y'$};
\draw[->, red, glow=red] (O) -- ({4*cos(50)}, {4*sin(50)}) coordinate(R);
\draw[blue, glow=orange] (R)|-coordinate (Q) (O);
\draw[glow=cyan] (O) -- ({4*cos(50)*cos(30)*cos(30)}, {4*cos(50)*cos(30)*sin(30)})-- (Q) -- cycle;
\draw[<->, Orchid] (1.25,0) arc (0:30:1.25cm) node[midway, right ]{$\theta_{11}$};
\draw[<->, Firebrick2] (30:1.25) arc (30:50:1.25cm) node[midway, right ]{$\theta_{12}$};
\draw[glow=yellow] (Q)--++({ 4*sin(50)*sin(30)*cos(30) }, { 4*sin(50)*sin(30)*sin(30) } )-- (R);
\end{tikzpicture}
\end{document}

Graph with "glowing" lines

Careful consideration needs to be taken on the order of the lines and glows, so that they are not painted on top of each other. Like in this zoom: Zoom on glow pattern

The easiest way to avoid problems are to draw all glows first(or on a background layer) and then the normal lines.


Edit:

This glow has rounded ends, and do not overwrite the original lines. Using the solution from Pass options to the scope that is internally created by preaction:

\documentclass[tikz, border=0.1 cm]{standalone}
\pgfdeclarelayer{back}
\pgfsetlayers{back,main}
\makeatletter
\pgfkeys{%
  /tikz/on layer/.code={
    \pgfonlayer{#1}\begingroup
    \aftergroup\endpgfonlayer
    \aftergroup\endgroup
  },
  /tikz/node on layer/.code={
    \pgfonlayer{#1}\begingroup
    \expandafter\def\expandafter\tikz@node@finish\expandafter{\expandafter\endgroup\expandafter\endpgfonlayer\tikz@node@finish}%
  },
}
\tikzset{%
glow/.style={%
preaction={#1, draw, line cap=round, line join=round, line width=0.5pt, opacity=0.04, on layer=back,
preaction={#1, draw, line cap=round, line join=round, line width=1.0pt, opacity=0.04, on layer=back,
preaction={#1, draw, line cap=round, line join=round, line width=1.5pt, opacity=0.04, on layer=back,
preaction={#1, draw, line cap=round, line join=round, line width=2.0pt, opacity=0.04, on layer=back,
preaction={#1, draw, line cap=round, line join=round, line width=2.5pt, opacity=0.04, on layer=back,
preaction={#1, draw, line cap=round, line join=round, line width=3.0pt, opacity=0.04, on layer=back,
preaction={#1, draw, line cap=round, line join=round, line width=3.5pt, opacity=0.04, on layer=back,
preaction={#1, draw, line cap=round, line join=round, line width=4.0pt, opacity=0.04, on layer=back,
preaction={#1, draw, line cap=round, line join=round, line width=4.5pt, opacity=0.04, on layer=back,
preaction={#1, draw, line cap=round, line join=round, line width=5.0pt, opacity=0.04, on layer=back,
preaction={#1, draw, line cap=round, line join=round, line width=5.5pt, opacity=0.04, on layer=back,
preaction={#1, draw, line cap=round, line join=round, line width=6.0pt, opacity=0.04, on layer=back,
}}}}}}}}}}}}}}
\begin{document}
\begin{tikzpicture}
\draw[glow=red] (0,0.5) -- (1,0.5);
\draw[glow=red] (0.5,0) -- (0.5,1);
\end{tikzpicture}
\end{document}

Zoom:

Zoom of glow crossing

Random glowing lines:

Random glowing lines

1
  • yes hpekristiansen, after a few tests, your code works better than I thought at first!! thanks again! Nov 5 '20 at 16:23
7

You can just draw some thick line in the background. This can be done either with the backgrounds library, by a preaction, just drawing the thick lines earlier, or combinations of these. If you set the opacity to nontrivial values, it can make sense to use a transparency group.

\documentclass[,varwidth,border=1pt]{standalone}
\usepackage[dvipsnames,svgnames,x11names,]{xcolor}
\usepackage{tikz}
%
\begin{document}
%
\begin{tikzpicture}[ >=latex,glow/.style={%
    preaction={draw,line cap=round,line join=round,
    opacity=0.3,line width=4pt,#1}},glow/.default=yellow,
    transparency group]
\draw[->] (-4,0)--(5,0) node[at end,above]{$x$};
\draw[->] (0,-1,0)--(0,5,0) node[at end,right]{$y$};
\draw[->] (0,0) coordinate(O) -- ({5*cos(30)},{5*sin(30)}) coordinate (XP)  node[pos=1.1]{$x'$};
\draw[->] (O) -- ({-5*sin(30)},{5*cos(30)}) coordinate (YP) node[pos=1.1]{$y'$};
\draw[->, red] (O) -- ({4*cos(50)}, {4*sin(50)}) coordinate(R);
\draw[glow] (R) -- (R|-O)coordinate (Q);
\draw[glow={cyan!50}] (Q) -- (O) -- 
({4*cos(50)*cos(30)*cos(30)},{4*cos(50)*cos(30)*sin(30)}) coordinate (A) -- cycle;
\draw[blue] (R)|- (O);
\draw[green] (O) -- (A)-- (Q);
\draw[<->, Orchid] (1.25,0) arc (0:30:1.25cm) node[midway, right ]{$\theta_{11}$};
\draw[<->, Firebrick2] (30:1.25) arc (30:50:1.25cm) node[midway, right ]{$\theta_{12}$};
\draw[orange,glow] (Q)--++({ 4*sin(50)*sin(30)*cos(30) }, { 4*sin(50)*sin(30)*sin(30) } )
coordinate (B)-- (R);
\end{tikzpicture}
%
\end{document}

enter image description here

6
  • Almost, but is not the same effect, you can observe the detail of the transparency from the center to the edge of the highlight, Thank you for your help! Nov 4 '20 at 18:38
  • this was my first step, tex.stackexchange.com/questions/73220/… Nov 4 '20 at 18:40
  • @AlejandroMunozOssa Then you may be looking for this answer.
    – user227987
    Nov 4 '20 at 19:39
  • I would also suggest the laser solution. An other way is to use a biquadratic patch from PGFPlots: tex.stackexchange.com/a/173310/8650 Nov 4 '20 at 20:39
  • Nice solution -one thing: transparency group does not work like this. It needs to be a scope with common transparency. -it will not prevent a darkening of the glow when overlapping. Nov 5 '20 at 4:36

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