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Full Version: Sugarloaf Cabochon ?!

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From: BurrMan
17 Apr 2022   [#6] In reply to [#1]
Here is a way to get close...



then, if you want those 4 edges to be harder, you can create some lines and trim some edge loops near, like in poly modeling and it will harden the edges you want. Takes just a bit more work to be sure you keep supported polygon types...
From: BurrMan
17 Apr 2022   [#7] In reply to [#6]
Here might be a bit easier using the "Loft to a Point" option.


From: TOM (SIRTOM)
17 Apr 2022   [#8]
Oh wow you are awesome, thank you so much to you all
for those amazing guides - fantastic !!
From: Phiro
17 Apr 2022   [#9]
another proposition... an intersection of spheres

4 spheres made with circular array.

You boolean intersect them.
Next you cut to have only the mid top.

Next you chamfer the bottom.

I have made a second version with opposite spheres scaled with 0.1 mm less if you want the edged top.

Adapt the height as you want...


To have surfaces for the claws, rotate your stone and cut with a curve.

All steps inside the 3dm file



Attachments:
cabo_tests.3dm

Image Attachments:
2022-04-18_05h52_52.png 


From: bemfarmer
18 Apr 2022   [#10]
Here are some multiviews, video, and dimensions:
https://www.rafjewels.com/search?q=emerald%20sugarloaf%20diamond

- Brian
From: Grendel
19 Apr 2022   [#11]
Looking at google pics it seems like they very a little bit if they come to a point or not so that is going to be hard to find a cad profile for the requirements. I did find a reference here though with a description, I used a point in this example.

https://emeralds.com/education/all-about-emerald-cabochons/

Bemfarmer already showed the source..

Image Attachments:
Sugarloaf.jpg 


From: TOM (SIRTOM)
19 Apr 2022   [#12]
Pilou, bemfamer, Death, Burrman, Phiro, Grendel, you are awesome and your input
is very much appreciated.

This Cabochon shape is really interesting, it looks like four symmetrical planes with
a curved tip and the very top unifying all four surfaces being additionally rounded in
a bit different way.

In regard of this endeavour I stumbled over the great little Squircle Script - is there a
difference in it to the "perfect ellipse" script which I was unable to find ?

TOM
From: bemfarmer
19 Apr 2022   [#13] In reply to [#12]
I think that the "super-ellipse" has more generalized, elaborate mathematics, than the squircle script.
(The squircle is a subset of the super-ellipse...)
(I like Burr's method, for the Cab.)

The squircle shape for the outline of the gem is nice.
The lower portions of the Cab gem seem to vary, and are important for mounting...
Read that the bottom is often not polished, for light reasons, and can be flat or rounded.
It is difficult to cut, for perfect symmetry. Have not seen the special tool machine which could be used...

- Brian
From: TOM (SIRTOM)
19 Apr 2022   [#14] In reply to [#13]
The Squircle (still strugelling with this word ;-)) script is really useful.

Taking a closer look at available photo material it seems
that the 4 edges start almost completely rounded at
the bottom sharpening towards the tip. The tip itself
being a surface of its own filling the gap between
the four surfaces.
From: Barry-H
19 Apr 2022   [#15] In reply to [#14]
Hi Tom,
perhaps this method will give you the rounded peak needed.
I started with a square and added mid points to each side.
Then selected the mid points and scaled to give the desired curvature,
Offset copies made and added point for peak then lofted as per Burr's video.
Added a fillet running diagonal from corner to corner.
The other diagonal same radii but requires a second fillet set for the peak area to be slightly smaller.
hope that makes sense.
Cheers
Barry



Image Attachments:
Fillet Peak.png 


From: BurrMan
19 Apr 2022   [#16] In reply to [#12]
Here is another option...

Since it seems the surgarloaf is more of an "artistic grind" and not really a mathematically produced result, you can change the base shape and all the angles of the surface structure, along with Blend parameters to "Eyeball" some various results... All smooth.


From: bemfarmer
19 Apr 2022   [#17]
Sugarloaf cut video. Not in English (India).
https://www.youtube.com/watch?v=dsfqdqgxEyE

- Brian

Google search of "Cabo Gem Cut" shows several videos, (but not for sugarloaf), and the grinding equipment.
From: TOM (SIRTOM)
19 Apr 2022   [#18] In reply to [#16]
Amazing approach, Burrman. The video shows you using the Superellipse script.
Is there any difference to the Squircle script ?
From: bemfarmer
20 Apr 2022   [#19] In reply to [#18]
It is Burr's video that you refer to?

- Brian
From: TOM (SIRTOM)
20 Apr 2022   [#20]
Uh I guess I mixed up your names ... Yes, the Video shows Burrman using
the Superellipse script and as I did not find this one (I am using the "Squircle")
I wondered about the differnces.
From: bemfarmer
20 Apr 2022   [#21] In reply to [#20]
The superellipse2d script is from 2013, and includes a squircle, I think as a subset.

https://moi3d.com/forum/index.php?webtag=MOI&msg=5616.1

About February 2022, a different squircle, using a different math formula, was created, the Fernandez-Guasti squircle. (Later in above link.)
This version is not a subset of superellipse2d. (?)

- Brian

I looked up the pronunciation of squircle. Combine the rodent squirrel with ircle.
(still hasn't made it into spellchecker :-)
From: Phiro
20 Apr 2022   [#22]
On the first picture of this thread and in the video we see, the Sugarloaf Cabochon have 4 faces with edges.
With the video, I discover the render of this cut, that I see very rarely in stores.
Very nice cut...
From: TOM (SIRTOM)
20 Apr 2022   [#23] In reply to [#21]
Thank you Disovered lots if scripts at the link you posted and will give them a try.
From: BurrMan
20 Apr 2022   [#24] In reply to [#23]
Hi Tom,
Brian is the creator of these scripts. He has made several of the "mathematical formula" scripts that create well known geometrical shapes.

He is best to answer about them and if there is any difference (or similarity)
From: TOM (SIRTOM)
20 Apr 2022   [#25] In reply to [#24]
Since this impossible word "Squircle" nauseated my mind it mixes up the names Burrmen Benfarmer and Brian -sorry ;-)

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