Re: Problem/bug with ends of thick lines in graphics

• To: mathgroup at smc.vnet.net
• Subject: [mg88443] Re: Problem/bug with ends of thick lines in graphics
• From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
• Date: Mon, 5 May 2008 06:15:43 -0400 (EDT)
• References: <fvhe27\$3t8\$1@smc.vnet.net>

```Hi,

Plot[x, {x, 1/3, 3/4}, PlotRange -> {{0, 1}, {0, 1}},
PlotStyle -> {AbsoluteThickness[20]}] /.
Line[pnts_] :> {AbsolutePointSize[20], Point[pnts]}

may help in this case. But AFAIK Mathematica has no directive
to set the line ends.

Regards
Jens

David Reiss wrote:
> In a quick search of things I haven't found a mention of the following
> simple graphics issue and I'm checking in with the group to see if
> there is a memory of its mention and if there is a simple fix (and
> which is not a complicated hack) that I've not been able to come up
> with.
>
> Consider the following graph:
>
> Plot[x, {x, 1/3, 3/4}, PlotRange -> {{0, 1}, {0, 1}},
>  PlotStyle -> {AbsoluteThickness[20]}]
>
> When you plot it you will see that the line's ends are not
> rectangular, whereas you would certainly want them to be so. (An
> alternative would be to have them be rounded, for example, but the
> question will remain the same whatever your preference is.)  Rather
> they appear as polygonal in a way inconsistent with the line itself.
>
> One assums that this is an artifact of how the line is rendered based
> on the individual line segments, and that that segmental rendering has
> to do something with how a segment relates to the segments on either
> side of it.  The lack of a segment beyond the end segment presumably
> runes the algorithm for rendering in a way that leads to this
> appearance.
>
> I have two related questions here.  The first is how, if at all
> possible, to fix this in a general way through some specific options
> settings for the graphics function.
>
> The second is how, when exporting this graphic as, say, a PDF, to make
> it behave properly.
>
> There was a trick in pre version-6 Mathematica that would involve
> adding an explicit postscript command to the PlotStyle option.  Though
> this would not (I think) correct the screen appearance of the graphic,
> it would properly fix it when the graphic was exported to PDF or EPS.
> Here is an example of how it was done:
>
> Plot[x, {x, 1/3, 3/4}, PlotRange -> {{0, 1}, {0, 1}},
>  PlotStyle -> {{ PostScript["0 setlinecap"],AbsoluteThickness[20]}}]
>
> This, however, no longer works in Mathematica 6+ presumably because of
> the new way that graphics rendering is handled.
>
> Does anyone have any solutions to either or both of these issues?
>
> Thanks!
>
> --David
>

```

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