Confusing names for torus parameters

[eshmoylova]

Modelica.Mechanics.MultiBody.Visualizers.Advanced.SurfaceCharacteristics.torus ans Modelica.Mechanics.MultiBody.Visualizers.Torus use confusing names for the description of the parameters: ri and ro.
Visualizers.Torus defines:

ModelicaStandardLibrary/Modelica/Mechanics/MultiBody/Visualizers.mo

Lines 857 to 858 in 491ccf7

	parameter Modelica.SIunits.Radius ri=0.5 "Inner radius of torus" annotation(Dialog(enable=animation));
	parameter Modelica.SIunits.Radius ro=0.1 "Outer radius of torus (=width/2)"

And SurfaceCharacteristics.torus defines:

ModelicaStandardLibrary/Modelica/Mechanics/MultiBody/Visualizers.mo

Lines 2450 to 2451 in 491ccf7

	input Modelica.SIunits.Radius ri=1 "Inner radius of torus" annotation(Dialog);
	input Modelica.SIunits.Radius ro=0.2 "Outer radius of torus (=width/2)" annotation(Dialog);

Usually, the inner radius for a torus is usually defined as the radius of the hole and the outer one as the radius of the whole shape. For example, see this. So having inner radius to be greater than the outer one does not make sense.

Looking at the formula used in SurfaceCharacteristics, it looks like ri is used as the major radius and ro as the minor radius, as defined here.

It would be good if there was perhaps some reference given to how ri and ro are supposed to be interpreted.

[MartinOtter]

Simplest probably to change the description texts.

• ri: Distance from the center of the tube to the center of the torus,
• ro: Radius of the tube.

Would be good to add a figure to make this clear.

I agree, the naming of the parameters could be better. However, names such as major/minor radius are also not completely obvious.

[tobolar]

• ri: Distance from the center of the tube to the center of the torus,
• ro: Radius of the tube.

The description is fine. We can even use:

• ri: Major radius: distance from the center of the tube to the center of the torus,
• ro: Minor radius: radius of the tube.

Unfortunately, the parameter names riand roare confusing then since they imply thinking of inner and outer radii which is definitely false. Following Wikipedia, we could use

• R: Major radius: distance from the center of the tube to the center of the torus,
• r: Minor radius: radius of the tube.

Unfortunately, WolframMathWorld uses exactly those names for indicating the inner and the outer radius. :-(
Thus

Would be good to add a figure to make this clear.

is a must in this case.

[beutlich]

I am in favour to follow Wikipedia and go for:

• R: Major radius (distance from the center of the tube to the center of the torus)
• r: Minor radius (radius of the tube)

[beutlich]

I believe that this also was resolved by #3176.