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

Jim Lemon drj|m|emon @end|ng |rom gm@||@com
Tue Jul 21 11:00:26 CEST 2020

Hi Byron,
As in the help page, three types of arrows can be specified. 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.


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.
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