Ah. I probably used loft. I'll try your suggestion, BurrMan. Thanks.

That worked a charm. Thanks a lot.

Today's exercise I set for myself: to construct a regular icosahedron. With MoI's ease of use, this didn't take very long. Time from starting to look at the Wikipedia entry for Isocahedron to get some construction ideas until posting it here: 30 minutes.

Cuty!

Hi Hakon, you may also be interested in some of these previous discussions on polyhedra construction:

http://moi3d.com/forum/index.php?webtag=MOI&msg=2140.46
http://moi3d.com/forum/index.php?webtag=MOI&msg=2153.1
http://moi3d.com/forum/index.php?webtag=MOI&msg=3798.1
http://moi3d.com/forum/index.php?webtag=MOI&msg=2275.1

There's also a collection of various models in 3DM format here:
http://www.rhino3d.nl/pythposter/pyth3dm-eng.html

- Michael

Thanks, Michael,

I did a dodecahedron after the icosahedron, so I figured that one out on my own after a quick Wikipedia lookup. It took a little bit longer, though.

I'm not really interested in just the finished shapes as from your last link, at least not right now when I am trying to learn how to use MoI, working with construction lines, setting coordinate, distance or angle constraints, and trying to think more in 3D. It might be useful knowing where to find them some day, though, so thanks for the link.

I have moved on from regular polyhedra to figuring out how to construct gems from cutting charts. That is a bit more difficult, but I think I am on the right track. First time I've done anything very trigonometrical since school, but MoI's construction lines are extremely helpful and powerful. So is rail revolve for quickly constructing cutting facets.

Seems I might get MoI for Christmas from my wife, so I can just keep going once my 30-day trial is over.

Yesterday evening's exercise is completed, with a brilliant cut diamond exactly to the specifications in the cutting chart. It took a few hours, but I now I could do a new one a lot quicker, having a bit of a routine for it.

I think I'll probably do one more just to see how my routine works on another chart before moving on to something else.

Do you have a link to the gem charts?
(I did an asschur cut a while back.)
- Brian

Hello, Brian,

I found it on http://www.facetdiagrams.org/

Here is the specific one I used: http://www.facetdiagrams.org/database/files/pc01006.html

An illusion star cut. Far more complex and more challenging than a brilliant as I had to rethink my method once the cut bases weren't all regular polygons anymore. But, with what I've learnt from doing that today, I can now do any gem with exact precision based on a cutting chart, so it's been a useful exercise.

For this one, I actually started with an extruded 48 facet base and almost literally cut the diamond face by face in MoI according to the cutting chart. I can't see any other way of doing it with the same precision. One could probably eyeball it and make something that looked nice much faster, but angles would be wrong, and so realistic ray tracing would reveal imperfections in the cut.

This one doesn't look as good in a static image. I guess it's one of those cuts that really only come into their own once the diamond is subject to constant movement.

Cool!
Have you some blueprints of these sort of things ?

Thanks, Pilou,

I use the cutting charts as found on http://www.facetdiagrams.org/

I might make a tutorial one day soon describing how to cut the gems in MoI with absolute precision. It's not the most straightforward thing to do.

Thanks for the info!

Moi is perfect for precise things like this. There is an input box at the bottom of the screen where you can input angels and other things for precise distances, angles, etc.

"""""I might make a tutorial one day soon describing how to cut the gems in MoI with absolute precision.""""""""""""""""""

Me likey.... Please. :)

BurrMan, until I do make a tutorial, I did find someone else online who use a method very similar to the one I devised. His method is described here: http://www.3dlapidary.com/HTML/Facets.htm and it should work well in any 3D program.

The website also has a lot of finished gem files, though some conversion might be necessary. There are Rhino files there, which supposedly should work in MoI, but when I tried opening them, nothing showed up on my screen. Not sure if there's a version mismatch as some of these seem rather old. I have started converting some of the .obj and .dxf files, though. As much fun as it is to make these oneself, it is time consuming (though, that is perhaps part of the fun too as long as you consider it a hobby), and it's nice to have a collection of finished gemstones on hand, too, for other jewellery work.

Totally ignoramus: as I see all lines are straigt lines does it possible to have curves in a daimond ?

There is no mechanical reason not to have curved lines in diamonds - especially virtual ones. I guess the facet cuts have developed over time to make sure that all the light coming from above the gem is reflected back up inside the gem to get the most interesting play of light when you look at it. Curved shapes would have a different effect, and there's nothing stopping you from experimenting with that to see what happens if you have access to a realistic renderer where you can adjust refractive indices and where you get realistic caustic effects.

Metropolis Light Transport is what I used.
...and you have to know something about the IoR (Incident of Refraction & Reflection) of the gem material.
The type of spot lighting is also crucial.

FYI - shayno posted some gemstone 3DM files a while back here:

http://moi3d.com/forum/lmessages.php?webtag=MOI&msg=4423.4

Ed