Hi Tom,

I used Hypotrochoid script to emulate your inner curve, with a:b ration of 5:1, a = 10, b = 2, c = 4.5 seems to be a close match.

Per Michael's suggestion, I tried offset for a larger curve, with 4 of 5 lobes working well.
I manipulated one lobe with trims and joins and circular array, and join, to match your drawing...
May try again after work.

- Brian

Hi Tom, can you please post the .3dm model file with the epicycloid curve in it that won't offset?

- Michael

Post deleted.
Thanks to Michael and Tom for lesson on unchecking Trim in Offset command in following messages.

Bothsides checkbox is also interesting.

- Brian

Hi Michael,

It is possible to offset, but after that,
I have to trim and blend, etc.

I am going through many variations and itrations, so it would
be a time saver to generate the desired curve with one click.

I tried the script fatlines but it causes a crah when working with an Epicyloid.

Thank you Brian, Ill have a look !

Hi Tom, if you could please post the .3dm file with the curve in it, instead of only screenshots it could make it easier to give suggestions.

From what I tell from your latest screenshot there, it looks like you should just uncheck the "Trim" option in Offset so that it will generate the full curve for you instead of trying to cut out pieces at self intersections.

- Michael

- Fatlines with very thiny values (0.1, or 0.05) by Max Smirnov http://moi3d.com/forum/index.php?webtag=MOI&msg=7594.31
- Kill original lines
- increase size
- Trim All

Hi Michael,

Sorry, I had upload but forgot to take a second look.

Anyway you gave me the key - I were not aware about the trim function in the offset
command so I am happy to have learnt about another function former unknown to me.

Back to MOI which fits like a bespoke glove for my work as an artist and designer
who wants to visualize inmediately what he has in mind without being distracted by a myriad
of buttons and commands ! I am really happy that I discovered your little gem a while ago.

No problem Tom, I'm glad that offset will work for you!

@Pilou - re: FatLines - FatLines uses curve booleans which is not really expecting to work with self intersecting curves like in this case.

- Michael

Here is an update to the _CycloidInterp script, renamed to _CycloidTrochoid.

This script plots a Trochoid or Cycloid on the x axis.
A common Trochoid has the bRadius equal to the aRadius, and is a Cycloid.
Interpcurve factory is used, to avoid cusp rounding.
Rewritten by Brian McMillin, September 2018.
A Brachistochrone is an inverted Cycloid.
A Gerstner wave is a trochoidal wave.
If b>a, the trochoid is a prolate cycloid.
If b<a, the trochoid is a curtate cycloid.

Note the different behavior of the display of the ignore checkbox,between MoI3 and MoI4.
For MoI4, the three lines of text are centered with the checkbox.
For MoI3, the first line of text is horizontal to the checkbox, with the other three lines below. (A preferred look???)

Can the (vertical?) centering be changed in the MoI4 display of the .htm file?

- Brian

Script updated 9/25/2018, with Michaels input, if the 3 people who downloaded it want the update.

Edit, Only one cycle is plotted, due to cusp problem with 2+ cycles.

Hi Brian, re: checkbox positioning, it is possible to change that one checkbox's position by putting this in the head section of your _CycloidTrochoid.htm file:

		<style>
			#ignore_bRadius {
				align-items:flex-start;
			}

			#ignore_bRadius .checkbutton_box {
				margin-top:0.2em;
			}
		</style>

- Michael

Thank you Michael

That works.
Unfortunately, the values of aRadius and bRadius are now set to zero, in MoI4, but are ok in MoI3 :-)
?

- Brian

Hi Brian,

re:
> Unfortunately, the values of aRadius and bRadius are now set to zero, in MoI4, but are ok in MoI3 :-)

That's a bug in v4 with handling whitespace characters in the default value. If you remove the line break for the default="" attributes that should avoid the bug right now.

So where you currently have:

			<tr>
				<td>aRadius</td>
				<td><input id="aRadius" class="numericinput" default="10
				" style="persist:true;"></td>
			</tr>

Remove the line break like so:

			<tr>
				<td>aRadius</td>
				<td><input id="aRadius" class="numericinput" default="10" style="persist:true;"></td>
			</tr>

I'll fix it up for the next v4 beta, thank you for reporting it.

- Michael

Thank you Michael.
The script is working again in MoI4, and continues to work in MoI3.

The white space was introduced unintentionally, while removing decimals, a day or so ago :-)
...5 or 6 or so decimals were causing occasional shift of the htm screen to the left, a fraction of an inch, in MoI3, but not in MoI4...

- Brian

The _CycloidTrochoid script is now updated, a few posts back.