Brain melting please help

Hi I’m new to 3D design and I’m trying to create the attached shape I can model it flat but can’t get the facets to work.I’m sure it’s quite simple but have had no luck so far can anyone suggest how I could go about this please image|375x500](upload://sagjPLXFneGDa82u7IAtHZIFA2S.jpeg)

Hi can you upload the image again? I think the code got mangled last time…

Hello sorry about that picture is now attached

Thank you

Just create a single Tetrahedron body then use rotate function to complete the design. Of course you have to do some mathematics.

That will result in curved sides. If I understand the goal, it’s to have flat triangular facets. I think you’ll have to create a three-sided pyramidal shape, make 11 copies, union them together to get the “Star of David” core. The other facets appear not to be equilateral triangles, so they’d have to be created separately.

I did mine by figuring the cut angles and rotating + subtracting bodies from a cylinder. You have 3 different cuts. I would approach it like a 6 sided object. Once you have the correct angle, simply rotate the the flat body 60 degrees and subtract. (see the top 6 triangles and the bottom 6 below them?) That will achieve the crown cuts. Then you have to figure the angle for the 12 upper girdle cuts.

In mine (see below) I drew a side profile on a construction plane, rotated it to create the 8 main features. I created a construction plane at the girdle and drew a top profile. That helped me figure the cut angle with the visual profile and top drawing. Note: you can create a construction plane between 3 points (See the triangles? :wink: from those I created a construction plane drew and extruded a body to cut from the cylinder, rotated 7 times and cut. I did this for each of the main cuts). Now some of the complex girdle cuts I couldn’t find the correct angles documented so I guessed.

It’s a reasonable facsimile of a cut gem. I got a little lazy in the end so it’s not very accurate. I started by trying figure how Gem cutting machines worked hoping to get face angle info, but gave up (lazy)

I got my ideas from sites like this Cuts of gemstones | Gemstone information at Rocks & Co.

Try the subtraction/rotation method using dummy bodies like this.

Old school geometry doesn’t need numbers much…

1st create a vertical section of the gem from top dead centre to the longest outer point. Then rotate 6 times at 60deg and subtract each time:

Subtract and rotate 60deg as before


This is brilliant!! Thank you so much for taking the time to screen shot your process. I shall try this tonight

Wow your gem is brilliant I will try this later thank you so much for your help

Wow, this is very smart.

I’d do anything to avoid getting a calculator out :joy:


By the way - congrats on another mention on the Apple event today…

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Thank you! :slight_smile:


Excellent work, certainly good ideas to try for the future, thank you

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@milouchien Precision is necessary at times, and having a scientific calculator as data value entry would be awesome. No need for a physical one, a virtual one will do… and of course have the option to toggle it on or off. I’ll keep on requesting this every time somebody mentions a calculator, @Istvan.

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No argument there - it’s in harmony with the quality of the rest of the thinking behind Shapr.

In my defence in this case we were trying to keep @Em81 s brain from melting so I tried to do it the spatial rather than the calculated way… :slightly_smiling_face:

@OserCAD: Better yet, It would be great if Shapr3D allowed arithmetic, including functions, to be entered in dimensions. Fusion 360 supports this.

Calculator :innocent:

Let me know how you get on and if you need more help.

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