[R] rgl terminology: the definitions of "thickness" and "width" in rgl

[Duncan Murdoch]

On 21/07/2020 5:00 a.m., Jim Lemon wrote:
> Hi Byron,
> As in the help page, three types of arrows can be specified.

Actually four types:  rotation, extrusion, lines, flat.  But the rest of 
your answer is right.

Duncan Murdoch

  In the
> "rotation" type, "width" is the parameter that determines the diameter
> of the cylindrical shaft as a fraction of the "barb", the cone at the
> end. In the default "extrusion" arrow, "thickness" is the fraction of
> the "width" of the shaft. Effectively how thick the fettuccine is
> relative to its width. Thickness doesn't seem to affect the "lines" or
> "flat" type, with the latter apparently of zero thickness.
> 
> Jim
> 
> On Tue, Jul 21, 2020 at 11:39 AM Byron Dom via R-help
> <r-help using r-project.org> wrote:
>>
>> I'm struggling to come up to speed with rgl. At the moment, I'm struggling with the function arrows3d(). In the R documentation for that, two parameters/arguments are mentioned: "thickness" (of the arrow's shaft) and "width" (of the arrow's shaft).
>> Naively, I would expect the arrow's shaft under normal circumstances to be cylindrical and its width or thickness would reduce to the single parameter "diameter." Then in some cases like plotting a 2-dimensional arrow on a 2-dimensional surface embedded in a 3D space, things like "width" would have an obvious meaning.
>> Would someone explain this to me, including the difference between width and thickness.
>> Thanks in advance.
>>
>>          [[alternative HTML version deleted]]
>>
>> ______________________________________________
>> R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
> 
> ______________________________________________
> R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>