How to draw a coil such that you can see if it's right or left handed?

If I draw a coil in tikz I usually do something like this:

documentclass[tikz]standalone usetikzlibrarydecorations.pathmorphing,patterns begindocument begintikzpicture draw[decoration=aspect=0.3, segment length=3.2mm, amplitude=3mm,coil,decorate,opacity=0.9] (1,0) -- (3,0); endtikzpicture enddocument

Which looks like this:

enter image description here

In some cases (for example in eletrodynamics) it might matter if the coil is right or left handed.

How can I modify the code above such that it looks like this:

enter image description here

If you have another, maybe better way to visualize the direction I am interested in it too.

The image quality of your second image is not very good. Can you clarify which aspect of it you'd like to replicate in your own image? There seem to be a change in line colour/line width as well as a small gap where the wire overlaps, but it is hard to see clearly in this pixelated image.

– samcarter
Sep 6 '18 at 12:43

It only matters in a schematic for transformers. One typically adds a dot toward one end of the coil to indicate polarity.

– John Kormylo
Sep 6 '18 at 12:52

@samcarter I want the line with change and the little gap.

– Julia
Sep 6 '18 at 13:27

2 Answers
2

The starting point of all this is the code in pgflibrarydecorations.pathmorphing.code.tex. I acknowledge a comment by joojaa that pointed out that the halo was not quite right in the original answers. I also appreciate a comment by Robert Harvey, who encouraged me to clean up. What I did is to modify the coil decoration of the decorations.pathmorphing library. There is still a lot of room for improvement. The keys in the beginning allow you to adjust the color, opacity, width of coil and additional width of the halo, I hope the names I gave to these parameters are self-explanatory.

pgflibrarydecorations.pathmorphing.code.tex

coil

decorations.pathmorphing

enter image description here

documentclass[tikz,border=3.14mm]standalone usetikzlibrarydecorations.pathmorphing pgfkeys% /pgf/decoration/.cd, 3d coil color/.store in=TDCoilColor, 3d coil color/.initial=black, 3d coil color=black, 3d coil width/.store in=TDCoilWidth, 3d coil width/.initial=0.4pt, 3d coil width=0.4pt, 3d coil dist/.store in=TDCoilDist, 3d coil dist/.initial=0.6pt, 3d coil dist=0.6pt, 3d coil opacity/.store in=TDCoilOpacity, 3d coil opacity/.initial=1, 3d coil opacity=1 makeatletter % https://tex.stackexchange.com/a/219088/121799 tikzsetget stroke color/.code=% expandafterglobal% Jump over, now we have global expandafterlet% Jump over now we have globallet expandafterpgfsavedstrokecolor% Jump we have globalletpgf... csnamestringcolor@pgfstrokecolorendcsname% Finally expand this and put it at the end , % globalletpgf... in expanded form restore stroke color/.code=pgf@setstrokecolor#1, defpgfpoint@onthreedcoil#1#2#3% pgf@x=#1pgfdecorationsegmentamplitude% pgf@x=pgfdecorationsegmentaspectpgf@x% pgf@y=#2pgfdecorationsegmentamplitude% pgf@xa=0.083333333333pgfdecorationsegmentlength% advancepgf@x by#3pgf@xa% advancepgf@x by-initialoffset pt% % coil decoration % % Parameters: pgfdecorationsegmentamplitude, pgfdecorationsegmentlength, pgfdeclaredecoration3d coilinitial stateinitial[width=0.25*pgfdecorationsegmentlength+pgfdecorationsegmentaspect*pgfdecorationsegmentamplitude, next state=coil, persistent precomputation= tikzsetget stroke color pgfmathsetmacroinitialoffset0.25*pgfdecorationsegmentlength+pgfdecorationsegmentaspect*pgfdecorationsegmentamplitude ] % pgfpathmovetopgfpointorigin pgfsetstrokecolorTDCoilColor pgfsetstrokeopacityTDCoilOpacity pgfsetlinewidth1.5*TDCoilWidth pgfpathcurveto pgfpoint@oncoil0 0.5551 pgfpoint@oncoil0.445 1 2 pgfpoint@oncoil1 1 3 pgfusepathstroke pgfcoordinateTD@coilastpgfpoint@oncoil1 1 3 statecoil[switch if less than=% 1.25pgfdecorationsegmentlength+% pgfdecorationsegmentaspectpgfdecorationsegmentamplitude+% pgfdecorationsegmentaspectpgfdecorationsegmentamplitude to last, width=+pgfdecorationsegmentlength] % line in the back % pgfsetstrokecolorTDCoilColor pgfsetfillcolorTDCoilColor pgfsetstrokeopacityTDCoilOpacity pgfpathmovetopgfpointanchorTD@coilastcenter pgfsetlinewidthTDCoilWidth pgfpathcurveto pgfpoint@onthreedcoil1.555 1 4 pgfpoint@onthreedcoil2 0.5555 pgfpoint@onthreedcoil2 0 6 pgfpathcurveto pgfpoint@onthreedcoil2 -0.5557 pgfpoint@onthreedcoil1.555-1 8 pgfpoint@onthreedcoil1 -1 9 pgfusepathstroke % % white background for front thick part % pgfsetstrokeopacity1 pgfsetstrokecolorwhite pgfsetfillcolorwhite pgfsetlinewidth1.5*TDCoilWidth+1.5*TDCoilDist pgfpathmovetopgfpoint@onthreedcoil1 1 3 pgfpathmovetopgfpoint@onthreedcoil1 -1 9 % draw forward pgfpathcurveto pgfpoint@onthreedcoil0.445-1 10 pgfpoint@onthreedcoil0 -0.55511.25 pgfpoint@onthreedcoil0 0 12.5 pgfpathcurveto pgfpoint@onthreedcoil0 0.55513.25 pgfpoint@onthreedcoil0.445 1 14.25 pgfpoint@onthreedcoil1 1 15 % draw the curve back pgfpathcurveto pgfpoint@onthreedcoil0.445 1 14 pgfpoint@onthreedcoil0 0.55512.75 pgfpoint@onthreedcoil0 0 11.5 pgfpathcurveto pgfpoint@onthreedcoil0 -0.55510.75 pgfpoint@onthreedcoil0.445-1 10 pgfpoint@onthreedcoil1 -1 9 pgfusepathstroke,fill % % draw the thick foreground path % pgfsetstrokecolorTDCoilColor pgfsetfillcolorTDCoilColor pgfsetstrokeopacityTDCoilOpacity pgfpathmovetopgfpoint@onthreedcoil1 1 3 pgfsetlinewidthTDCoilWidth % forward shifted + pgfpathmovetopgfpoint@onthreedcoil1 -1 9 pgfpathcurveto pgfpoint@onthreedcoil0.445-1 10 pgfpoint@onthreedcoil0 -0.55511.25 pgfpoint@onthreedcoil0 0 12.5 pgfpathcurveto pgfpoint@onthreedcoil0 0.55513.25 pgfpoint@onthreedcoil0.445 1 14.25 pgfpoint@onthreedcoil1 1 15 % draw the curve back shfted - pgfpathcurveto pgfpoint@onthreedcoil0.445 1 14 pgfpoint@onthreedcoil0 0.55512.75 pgfpoint@onthreedcoil0 0 11.5 pgfpathcurveto pgfpoint@onthreedcoil0 -0.55510.75 pgfpoint@onthreedcoil0.445-1 10 pgfpoint@onthreedcoil1 -1 9 pgfusepathstroke,fill % <- added pgfcoordinateTD@coilastpgfpoint@onthreedcoil1 1 15 statelast[width=.25pgfdecorationsegmentlength+% pgfdecorationsegmentaspectpgfdecorationsegmentamplitude+% pgfdecorationsegmentaspectpgfdecorationsegmentamplitude,next state=final] pgfsetstrokecolorTDCoilColor pgfsetstrokeopacityTDCoilOpacity pgfsetlinewidthTDCoilWidth pgfpathmovetopgfpointanchorTD@coilastcenter pgfpathcurveto pgfpoint@onthreedcoil1.555 1 4 pgfpoint@onthreedcoil2 0.5555 pgfpoint@onthreedcoil2 0 6 statefinal pgfpathlinetopgfpointdecoratedpathlast pgfusepathstroke tikzsetrestore stroke color/.expand once=pgfsavedstrokecolor makeatother begindocument begintikzpicture draw[decoration=3d coil color=blue,aspect=0.35, segment length=3.1mm, amplitude=3mm,3d coil, decorate] (0,0) -- (0,3); draw[decoration=3d coil color=red,3d coil opacity=0.9,aspect=0.45, segment length=3.1mm, amplitude=3mm,3d coil, decorate] (2,3) -- (2,0); draw[decoration=3d coil color=green!60!black,3d coil opacity=0.9,aspect=0.35, segment length=3.1mm, amplitude=3mm,3d coil, decorate] (4,3) to[out=0,in=90] (6,0); endtikzpicture enddocument

FUN: The mandatory animation can be made with the same preamble + usepackagetikzmarmots and

usepackagetikzmarmots

begindocument foreach X [evaluate=X as Y using sin(X)]in 0,10,...,350 begintikzpicture path[use as bounding box] (-1,-0.2) rectangle (1,4); draw[decoration=3d coil color=blue,aspect=0.35, segment length=(1.2+0.7*Y)*1mm, amplitude=3mm,3d coil, decorate] (0,0) -- (0,2); beginscope[shift=(-0.9,1+0.5*Y)] marmot[teeth,whiskers] endscope endtikzpicture enddocument

enter image description here

BONUS: A "complete" version, i.e. an analog of Jake's complete sines with a "closed" option (analogous to the closed zigzags.)

documentclass[tikz,border=3.14mm]standalone usetikzlibrarydecorations.pathmorphing makeatletter newififcoil@closed pgfkeys% /pgf/decoration/.cd, 3d coil color/.store in=TDCoilColor, 3d coil color/.initial=black, 3d coil color=black, 3d coil width/.store in=TDCoilWidth, 3d coil width/.initial=0.4pt, 3d coil width=0.4pt, 3d coil dist/.store in=TDCoilDist, 3d coil dist/.initial=0.6pt, 3d coil dist=0.6pt, 3d coil opacity/.store in=TDCoilOpacity, 3d coil opacity/.initial=1, 3d coil opacity=1, 3d coil closed/.code=coil@closedtrue % https://tex.stackexchange.com/a/219088/121799 tikzsetget stroke color/.code=% expandafterglobal% Jump over, now we have global expandafterlet% Jump over now we have globallet expandafterpgfsavedstrokecolor% Jump we have globalletpgf... csnamestringcolor@pgfstrokecolorendcsname% Finally expand this and put it at the end , % globalletpgf... in expanded form restore stroke color/.code=pgf@setstrokecolor#1, defpgfpoint@onthreedcoil#1#2#3% pgf@x=#1pgfdecorationsegmentamplitude% pgf@x=pgfdecorationsegmentaspectpgf@x% pgf@y=#2pgfdecorationsegmentamplitude% pgf@xa=0.083333333333pgfdecorationsegmentlength% advancepgf@x by#3pgf@xa% advancepgf@x by-generaloffset pt% % coil decoration % % Parameters: pgfdecorationsegmentamplitude, pgfdecorationsegmentlength, pgfdeclaredecoration3d complete coilinitial stateinitial[width=0.5*pgfdecorationsegmentlength, next state=coil, persistent precomputation=% from https://tex.stackexchange.com/a/25689/121799 pgfmathsetmacromatchinglengthpgfdecoratedinputsegmentlength / int(pgfdecoratedinputsegmentlength/pgfdecorationsegmentlength) setlengthpgfdecorationsegmentlengthmatchinglength pt tikzsetget stroke color pgfmathsetmacrogeneraloffsetpgfdecorationsegmentlength pgfmathsetmacroinitialoffset1.5*pgfdecorationsegmentlength pgfmathsetmacroauxoffset2.5*pgfdecorationsegmentlength ] % line in the back % pgfsetstrokecolorTDCoilColor pgfsetfillcolorTDCoilColor pgfsetstrokeopacityTDCoilOpacity pgfsetlinewidthTDCoilWidth ifcoil@closed begingroup defgeneraloffsetauxoffset pgfpathmovetopgfpoint@onthreedcoil1 1 15 pgfpathcurveto pgfpoint@onthreedcoil1.555 1 16 pgfpoint@onthreedcoil2 0.55517 pgfpoint@onthreedcoil2 0 18 pgfcoordinateTD@coilastpgfpoint@onthreedcoil2 0 18 pgfcoordinateTD@coilfirstpgfpoint@onthreedcoil1 1 15 pgfusepathstroke pgfsetstrokecolorTDCoilColor endgroup fi begingroup % defgeneraloffsetinitialoffset ifcoil@closed pgfpathmovetopgfpointanchorTD@coilastcenter else pgfpathmovetopgfpointorigin fi pgfpathcurveto pgfpoint@onthreedcoil2 -0.5557 pgfpoint@onthreedcoil1.555-1 8 pgfpoint@onthreedcoil1 -1 9 pgfusepathstroke % % white background for front thick part % pgfsetstrokeopacity1 pgfsetstrokecolorwhite pgfsetfillcolorwhite pgfsetlinewidth1.5*TDCoilWidth+1.5*TDCoilDist pgfpathmovetopgfpoint@onthreedcoil1 -1 9 % draw forward pgfpathcurveto pgfpoint@onthreedcoil0.445-1 10 pgfpoint@onthreedcoil0 -0.55511.25 pgfpoint@onthreedcoil0 0 12.5 pgfpathcurveto pgfpoint@onthreedcoil0 0.55513.25 pgfpoint@onthreedcoil0.445 1 14.25 pgfpoint@onthreedcoil1 1 15 % draw the curve back pgfpathcurveto pgfpoint@onthreedcoil0.445 1 14 pgfpoint@onthreedcoil0 0.55512.75 pgfpoint@onthreedcoil0 0 11.5 pgfpathcurveto pgfpoint@onthreedcoil0 -0.55510.75 pgfpoint@onthreedcoil0.445-1 10 pgfpoint@onthreedcoil1 -1 9 pgfusepathstroke,fill % % draw the thick foreground path % pgfsetstrokecolorTDCoilColor pgfsetfillcolorTDCoilColor pgfsetstrokeopacityTDCoilOpacity pgfpathmovetopgfpoint@onthreedcoil1 1 3 pgfsetlinewidthTDCoilWidth % forward shifted + pgfpathmovetopgfpoint@onthreedcoil1 -1 9 pgfpathcurveto pgfpoint@onthreedcoil0.445-1 10 pgfpoint@onthreedcoil0 -0.55511.25 pgfpoint@onthreedcoil0 0 12.5 pgfpathcurveto pgfpoint@onthreedcoil0 0.55513.25 pgfpoint@onthreedcoil0.445 1 14.25 pgfpoint@onthreedcoil1 1 15 % draw the curve back shfted - pgfpathcurveto pgfpoint@onthreedcoil0.445 1 14 pgfpoint@onthreedcoil0 0.55512.75 pgfpoint@onthreedcoil0 0 11.5 pgfpathcurveto pgfpoint@onthreedcoil0 -0.55510.75 pgfpoint@onthreedcoil0.445-1 10 pgfpoint@onthreedcoil1 -1 9 pgfusepathstroke,fill pgfpathmovetopgfpoint@onthreedcoil1 1 15 pgfpathcurveto pgfpoint@onthreedcoil1.555 1 16 pgfpoint@onthreedcoil2 0.55517 pgfpoint@onthreedcoil2 0 18 pgfcoordinateTD@coilastpgfpoint@onthreedcoil2 0 18 pgfusepathstroke endgroup statecoil[switch if less than=% 1.9*pgfdecorationsegmentlength to last, width=+pgfdecorationsegmentlength] % line in the back % pgfsetstrokecolorTDCoilColor pgfsetfillcolorTDCoilColor pgfsetstrokeopacityTDCoilOpacity pgfpathmovetopgfpointanchorTD@coilastcenter pgfsetlinewidthTDCoilWidth pgfpathcurveto pgfpoint@onthreedcoil2 -0.5557 pgfpoint@onthreedcoil1.555-1 8 pgfpoint@onthreedcoil1 -1 9 pgfusepathstroke % % white background for front thick part % pgfsetstrokeopacity1 pgfsetstrokecolorwhite pgfsetfillcolorwhite pgfsetlinewidth1.5*TDCoilWidth+1.5*TDCoilDist pgfpathmovetopgfpoint@onthreedcoil1 1 3 pgfpathmovetopgfpoint@onthreedcoil1 -1 9 % draw forward pgfpathcurveto pgfpoint@onthreedcoil0.445-1 10 pgfpoint@onthreedcoil0 -0.55511.25 pgfpoint@onthreedcoil0 0 12.5 pgfpathcurveto pgfpoint@onthreedcoil0 0.55513.25 pgfpoint@onthreedcoil0.445 1 14.25 pgfpoint@onthreedcoil1 1 15 % draw the curve back pgfpathcurveto pgfpoint@onthreedcoil0.445 1 14 pgfpoint@onthreedcoil0 0.55512.75 pgfpoint@onthreedcoil0 0 11.5 pgfpathcurveto pgfpoint@onthreedcoil0 -0.55510.75 pgfpoint@onthreedcoil0.445-1 10 pgfpoint@onthreedcoil1 -1 9 pgfusepathstroke,fill % % draw the thick foreground path % pgfsetstrokecolorTDCoilColor pgfsetfillcolorTDCoilColor pgfsetstrokeopacityTDCoilOpacity pgfpathmovetopgfpoint@onthreedcoil1 1 3 pgfsetlinewidthTDCoilWidth % forward shifted + pgfpathmovetopgfpoint@onthreedcoil1 -1 9 pgfpathcurveto pgfpoint@onthreedcoil0.445-1 10 pgfpoint@onthreedcoil0 -0.55511.25 pgfpoint@onthreedcoil0 0 12.5 pgfpathcurveto pgfpoint@onthreedcoil0 0.55513.25 pgfpoint@onthreedcoil0.445 1 14.25 pgfpoint@onthreedcoil1 1 15 % draw the curve back shfted - pgfpathcurveto pgfpoint@onthreedcoil0.445 1 14 pgfpoint@onthreedcoil0 0.55512.75 pgfpoint@onthreedcoil0 0 11.5 pgfpathcurveto pgfpoint@onthreedcoil0 -0.55510.75 pgfpoint@onthreedcoil0.445-1 10 pgfpoint@onthreedcoil1 -1 9 pgfusepathstroke,fill pgfpathmovetopgfpoint@onthreedcoil1 1 15 pgfpathcurveto pgfpoint@onthreedcoil1.555 1 16 pgfpoint@onthreedcoil2 0.55517 pgfpoint@onthreedcoil2 0 18 pgfusepathstroke pgfcoordinateTD@coilastpgfpoint@onthreedcoil2 0 18 statelast[next state=final] % line in the back % pgfsetstrokecolorTDCoilColor pgfsetfillcolorTDCoilColor pgfsetstrokeopacityTDCoilOpacity pgfpathmovetopgfpointanchorTD@coilastcenter pgfsetlinewidthTDCoilWidth pgfpathcurveto pgfpoint@onthreedcoil2 -0.5557 pgfpoint@onthreedcoil1.555-1 8 pgfpoint@onthreedcoil1 -1 9 pgfusepathstroke % % draw the thick foreground path % ifcoil@closed %pgfpointanchorTD@coilfirstcenter % % white background for front thick part % pgfsetstrokeopacity1 pgfsetstrokecolorwhite pgfsetfillcolorwhite pgfsetlinewidth1.5*TDCoilWidth+1.5*TDCoilDist pgfpathmovetopgfpoint@onthreedcoil1 1 3 pgfpathmovetopgfpoint@onthreedcoil1 -1 9 % draw forward pgfpathcurveto pgfpoint@onthreedcoil0.445-1 10 pgfpoint@onthreedcoil0 -0.55511.25 pgfpoint@onthreedcoil0 0 12.5 pgfpathcurveto pgfpoint@onthreedcoil0 0.55513.25 pgfpoint@onthreedcoil0.445 1 14.25 pgfpointanchorTD@coilfirstcenter % draw the curve back pgfpathcurveto pgfpoint@onthreedcoil0.445 1 14 pgfpoint@onthreedcoil0 0.55512.75 pgfpoint@onthreedcoil0 0 11.5 pgfpathcurveto pgfpoint@onthreedcoil0 -0.55510.75 pgfpoint@onthreedcoil0.445-1 10 pgfpoint@onthreedcoil1 -1 9 pgfusepathstroke,fill pgfsetstrokecolorTDCoilColor pgfsetfillcolorTDCoilColor pgfsetstrokeopacityTDCoilOpacity pgfpathmovetopgfpoint@onthreedcoil1 1 3 pgfsetlinewidthTDCoilWidth % forward shifted + pgfpathmovetopgfpoint@onthreedcoil1 -1 9 pgfpathcurveto pgfpoint@onthreedcoil0.445-1 10 pgfpoint@onthreedcoil0 -0.55511.25 pgfpoint@onthreedcoil0 0 12.5 pgfpathcurveto pgfpoint@onthreedcoil0 0.55513.25 pgfpoint@onthreedcoil0.445 1 14.25 pgfpointanchorTD@coilfirstcenter % draw the curve back shifted pgfpathcurveto pgfpoint@onthreedcoil0.445 1 14 pgfpoint@onthreedcoil0 0.55512.75 pgfpoint@onthreedcoil0 0 11.5 pgfpathcurveto pgfpoint@onthreedcoil0 -0.55510.75 pgfpoint@onthreedcoil0.445-1 10 pgfpoint@onthreedcoil1 -1 9 pgfusepathstroke,fill else % % white background for front thick part % pgfsetstrokeopacity1 pgfsetstrokecolorwhite pgfsetfillcolorwhite pgfsetlinewidth1.5*TDCoilWidth+1.5*TDCoilDist pgfpathmovetopgfpoint@onthreedcoil1 1 3 pgfpathmovetopgfpoint@onthreedcoil1 -1 9 % draw forward pgfpathcurveto pgfpoint@onthreedcoil0.445-1 10 pgfpoint@onthreedcoil0 -0.55511.25 pgfpoint@onthreedcoil0 0 12.5 pgfpathcurveto pgfpoint@onthreedcoil0 0.55513.25 pgfpoint@onthreedcoil0.445 1 14.25 pgfpoint@onthreedcoil1 1 15 % draw the curve back pgfpathcurveto pgfpoint@onthreedcoil0.445 1 14 pgfpoint@onthreedcoil0 0.55512.75 pgfpoint@onthreedcoil0 0 11.5 pgfpathcurveto pgfpoint@onthreedcoil0 -0.55510.75 pgfpoint@onthreedcoil0.445-1 10 pgfpoint@onthreedcoil1 -1 9 pgfusepathstroke,fill pgfsetstrokecolorTDCoilColor pgfsetfillcolorTDCoilColor pgfsetstrokeopacityTDCoilOpacity pgfpathmovetopgfpoint@onthreedcoil1 1 3 pgfsetlinewidthTDCoilWidth % forward shifted + pgfpathmovetopgfpoint@onthreedcoil1 -1 9 pgfpathcurveto pgfpoint@onthreedcoil0.445-1 10 pgfpoint@onthreedcoil0 -0.55511.25 pgfpoint@onthreedcoil0 0 12.5 pgfpathcurveto pgfpoint@onthreedcoil0 0.55513.25 pgfpoint@onthreedcoil0.445 1 14.25 pgfpoint@onthreedcoil1 1 15 % draw the curve back shifted pgfpathcurveto pgfpoint@onthreedcoil0.445 1 14 pgfpoint@onthreedcoil0 0.55512.75 pgfpoint@onthreedcoil0 0 11.5 pgfpathcurveto pgfpoint@onthreedcoil0 -0.55510.75 pgfpoint@onthreedcoil0.445-1 10 pgfpoint@onthreedcoil1 -1 9 pgfusepathstroke,fill fi pgfpathmovetopgfpoint@onthreedcoil1 1 15 ifcoil@closed %TD@coilfirst else pgfpathcurveto pgfpoint@onthreedcoil1.555 1 16 pgfpoint@onthreedcoil2 0.55517 pgfpoint@onthreedcoil2 0 18 fi pgfusepathstroke %pgfcoordinateTD@coilastpgfpoint@onthreedcoil2 0 18 statefinal pgfpathmovetopgfpointdecoratedpathlast tikzsetrestore stroke color/.expand once=pgfsavedstrokecolor makeatother begindocument begintikzpicture draw[decoration=3d coil color=red,aspect=0.35, segment length=3.1mm, amplitude=3mm,3d complete coil, decorate] (0,1) -- (0,6); draw[decoration=3d coil color=blue,3d coil opacity=0.9,aspect=0.5, segment length=2*pi*3cm/50, amplitude=5mm,3d complete coil, 3d coil closed, decorate] (5,3.5) circle (3); draw[decoration=3d coil color=green!60!black,aspect=0.5, segment length=3.1mm, amplitude=4mm,3d complete coil, decorate] (0,-1) -- (0,-6); draw[decoration=3d coil color=purple,3d coil opacity=0.9,aspect=0.5, segment length=2*pi*3cm/50, amplitude=3mm,3d complete coil, 3d coil closed, decorate] (5,-3.5) circle (3); endtikzpicture enddocument

enter image description here

The decorations in pgf, it's the most difficult, wonderful work, bravo!

– AndréC
Sep 6 '18 at 16:05

@AndréC Merci, but I am actually not really happy, What I would love to achieve is that it is not necessary to set the color, opacity and so on explicitly. And then there are more downsides. Assume I was able to achieve this, then the decomposition of the path in little segments has further downsides such as the fact that a dashed line will not look nice. So there is a lot of room for improvement...

– marmot
Sep 6 '18 at 16:09

Another beautiful piece of marmot magic!

– Max
Sep 7 '18 at 18:04

@Diaa Coil has a straight line because the length of one coil (i.e. the segment length) does not divide the length of the path. Coil2 uses a different approach in which the length of the coil is set to be 1/10 of the length of the path, which is why there is no straight line piece. To overcome the problem of leftovers you may use Jake's complete sines.

– marmot
Dec 17 '18 at 22:39

Coil

Coil2

@Diaa One would have to rewrite the style. The "problem" (I use parentheses because this is not at all a criticism of the nice macros) is that the path starts with an offset. If you replace in his code (90: 0.2 and 0.4) by (90: 0.2 and 0.4) coordinate(coilaux1-pgfkeysvalueof/pgf/decoration/mark info/sequence number) and (0,0)++(90: 0.2 and 0.4) by (0,0)++(90: 0.2 and 0.4) coordinate(coilaux0-pgfkeysvalueof/pgf/decoration/mark info/sequence number), you can access the start as (coilaux0-1) and the end as (coilaux1-n) with an appropriate n.

– marmot
Dec 17 '18 at 23:20

(90: 0.2 and 0.4)

(90: 0.2 and 0.4) coordinate(coilaux1-pgfkeysvalueof/pgf/decoration/mark info/sequence number)

(0,0)++(90: 0.2 and 0.4)

(0,0)++(90: 0.2 and 0.4) coordinate(coilaux0-pgfkeysvalueof/pgf/decoration/mark info/sequence number)

(coilaux0-1)

(coilaux1-n)

n

If you put negative values for aspect and amplitude, you can get the mirrored coil, add this in the @marmot's answer may complete the desired output; also I added an option using markings to get some similar drawing that uses scope and yscale to invert the marking, then a new variable to control the coil color,when the path is straight it has good result, markings path lacks bending good results.

aspect

amplitude

yscale

EDIT: Added a control for marking step to improve bending results.

RESULT:

enter image description here

MWE:

documentclass[tikz,border=20pt]standalone usetikzlibrarydecorations.pathmorphing,decorations.markings begindocument begintikzpicture[ CoilColor/.store in=coilcolor,CoilColor=black, Step/.store in=Step,Step=0.1, Coil/.style= double=black, draw=gray!50, decoration= #1, segment length=3mm, coil , decorate, , Coil2/.style= decorate, decoration= markings, mark= between positions 0 and 1 step Step with beginscope[yscale=#1] draw[xshift=9.2,fill,coilcolor!70!black] (0,0)++(-135: 0.2 and 0.4) .. controls +(-0.2,0) and +(-0.3,0) .. (90: 0.2 and 0.4) .. controls +(-0.33,0) and +(-0.23,0) .. (-135: 0.2 and 0.4); draw[white,line width=2pt] (0,0)++(90: 0.2 and 0.4) .. controls +(0.3,0) and +(0.2,0) .. (-45: 0.2 and 0.4); draw[fill=coilcolor,coilcolor] (0,0)++(90: 0.2 and 0.4) .. controls +(0.3,0) and +(0.2,0) .. (-45: 0.2 and 0.4) .. controls +(0.25,0) and +(0.35,0) .. (90: 0.2 and 0.4); endscope ] draw[Coil=aspect=-0.3,amplitude=-3mm,blue] (0,0) -- ++ (0,-3); draw[Coil=aspect=0.3,amplitude=3mm,red] (1.5,0) -- ++ (0,-3); draw[Coil=aspect=0.3,amplitude=3mm,green!50!black] (3,0) arc (90:0:3); draw[Coil=aspect=-0.3,amplitude=-3mm] (3,1) arc (90:0:4); draw[Coil2=-1,CoilColor=blue] (0,-4) -- ++ (0,-3); draw[Coil2=1,CoilColor=red] (1.5,-4) -- ++ (0,-3); draw[Coil2=-1,CoilColor=green!50!black,Step=0.065] (3,-4) arc (90:0:3); draw[Coil2=1,Step=0.048] (3,-3) arc (90:0:4); endtikzpicture enddocument

UPDATE:
Acording to @marmot's suggestion closing the gaps and drawing all the variations, using pgfdecoratedpathlength, /pgf/decoration/mark info/sequence number.

pgfdecoratedpathlength

/pgf/decoration/mark info/sequence number

RESULT:
enter image description here

MWE:

documentclass[tikz,border=20pt]standalone usetikzlibrarydecorations.markings begindocument begintikzpicture[ CoilColor/.store in=coilcolor,CoilColor=black, Step/.store in=Step,Step=0.1, Width/.store in=Width,Width=0.4, Coil2/.style= decorate, decoration= markings, mark= between positions 0 and 1 step Step with beginscope[yscale=#1] pgfmathparseint(pgfdecoratedpathlength/28.45*100*Step) edefHightpgfmathresult ifnumpgfkeysvalueof/pgf/decoration/mark info/sequence number=1 path (0,0)++(90: Hight/200 and Width) coordinate (b); fi ifnumpgfkeysvalueof/pgf/decoration/mark info/sequence number>1 coordinate (b) at (d); fi path (b) arc (90:-135: Hight/200 and Width) coordinate (a); path (b) arc (90:-45: Hight/200 and Width) coordinate (c); path (b)++(Hight/100,0) coordinate (d); draw[fill,coilcolor!70!black] (c) .. controls +(-0.175,0) and +(-0.275,0) .. (d) .. controls +(-0.325,0) and +(-0.225,0) .. (c); draw[white,line width=2pt] (b) .. controls +(0.3,0) and +(0.2,0) .. (c); draw[fill,coilcolor] (b) .. controls +(0.275,0) and +(0.175,0) .. (c) .. controls +(0.225,0) and +(0.325,0) .. (b); endscope ] draw[Coil2=-1,CoilColor=red,Step=0.15] (0.5,0) -- ++ (0,-3); draw[Coil2=1.5,CoilColor=magenta] (1.5,0) -- ++ (0,-3); draw[Coil2=1,CoilColor=green!70!black,Step=0.02] (0,-4) to [in=90,out=0] ++(2.5,-1) to [in=180,out=-90] ++(2.5,-1) to [in=-90,out=0] ++(2,1.5) to [in=-90,out=90] ++(0.5,3) arc (0:90:2); draw[Coil2=-1,CoilColor=green!50!cyan,Step=0.02] (0,-5) to [in=90,out=0] ++(1.5,-1) to [in=180,out=-90] ++(4,-1) to [in=-90,out=0] ++(3,2.5) to [in=-90,out=90] ++(0.5,4.5) arc (0:90:2); draw[Coil2=1,CoilColor=cyan!30!blue,Step=0.05] (5.7,-2) arc (360:0:1.5); draw[Coil2=-1,CoilColor=cyan!70!blue,Step=0.05] (6.5,-2) arc (360:0:1.5); endtikzpicture enddocument

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