Search found 78 matches

by guy
Fri Aug 21, 2015 9:32 am
Forum: Stella Feature Requests
Topic: Plane tilings
Replies: 0
Views: 15635

Plane tilings

Would it be possible for Stella to explore plane tilings as well as polyhedra? There seem to be two approaches to tiling: Symmetries (e.g. kaleidoscopes) in the plane can generate tilings, much as spherical ones generate polyhedra. There are even some "dense" or overlapping tilings analogous to star...
by guy
Fri Aug 21, 2015 8:48 am
Forum: Stella Forum
Topic: How does Stella4D determine the dual?
Replies: 31
Views: 61559

First, please could you shrink that huge screenshot? It is vastly bigger than my poor screen and makes all the text shoot off to the right. Duality of polyhedra exists at several different levels. Sometimes, a polyhedron will have a dual at one level but not at another. Combinatorial or abstract dua...
by guy
Thu Aug 13, 2015 7:16 pm
Forum: Polyhedra
Topic: Archimedean polyhedra with missing faces
Replies: 1
Views: 12383

I do not think there is any serious mathematical approach to them, they are just symmetrical shapes which look a bit like polyhedra and have the same symmetries. Technically they are finite bounded manifolds whose boundary is disjoint, but that applies to anything with holes punched through its surf...
by guy
Thu Jul 23, 2015 8:14 pm
Forum: Stella Feature Requests
Topic: Truncation of Polyhedra
Replies: 1
Views: 7226

Hi Rob, 'Fraid I am still firmly wedded to Linux and can't be ***ed with WINE so my copy of Stella is equally firmly parked for the foreseeable. I would think that all the basic operations one encounters - truncation, bevelling, runcination, etc. - would be worth implementing, if only to help us lea...
by guy
Mon Jul 06, 2015 7:20 pm
Forum: Stella Forum
Topic: N-gonal pyramids
Replies: 2
Views: 10022

Of course, a 20-sided pyramid with something like a {20/9} star icosagon base can have equilateral sides. In general, for an {n/m}star base, n/m < 6 will allow a uniform star pyramid. Also, n and m must be co-prime (no common factor) or you get a compound, and m < n/2 or you get a backward duplicate...
by guy
Thu Nov 06, 2014 1:50 pm
Forum: Stella Forum
Topic: Equilateral convex polyhedra (new class after 400 years?)
Replies: 27
Views: 72611

Certainly some polyhedra can't be given equal edge lengths unless they lose their convexity, like many of the duals of the Archimedean solids. Yes of course, all those funny groupings of triangles round a vertex for a start. Something like a heptagonal pyramid requires its equilateral morph to be w...
by guy
Tue Nov 04, 2014 8:42 pm
Forum: Stella Forum
Topic: Equilateral convex polyhedra (new class after 400 years?)
Replies: 27
Views: 72611

robertw wrote:I've also just realised that pretty much every near miss included with Stella can be adjusted to an equilateral version.
H'mm. Setting symmetry aside, are there any convex polyhedra that can not be adjusted to equilateral form? Whole families? Non-convex? What are the rules?
by guy
Sun Nov 02, 2014 3:32 pm
Forum: Stella Forum
Topic: Equilateral convex polyhedra (new class after 400 years?)
Replies: 27
Views: 72611

By all, that's wonderful. Why solve equations when you can jiggle about?
by guy
Sat Nov 01, 2014 6:48 pm
Forum: Stella Forum
Topic: Equilateral convex polyhedra (new class after 400 years?)
Replies: 27
Views: 72611

I also need a way to ... maybe even to generate Goldbergs with equal edge lengths as per the paper. I think that will require the solution of multiple simultaneous equations, there are no shortcuts for such arbitrary metric equalities in projective reciprocation. Can one even assume that all the ve...
by guy
Sat Nov 01, 2014 6:37 pm
Forum: Stella Forum
Topic: Equilateral convex polyhedra (new class after 400 years?)
Replies: 27
Views: 72611

Well Goldberg was interested in cages, and probably not interested in flat faces, because he was looking at molecular arrangements. I think these guys just realised, while doing the same thing, that they could expand this to say something interesting about polyhedra, as an aside to their molecular ...
by guy
Thu Oct 30, 2014 8:40 pm
Forum: Stella Forum
Topic: Equilateral convex polyhedra (new class after 400 years?)
Replies: 27
Views: 72611

Hi Robert, Yes, I think your remarks about the other types of equilateral polyhedron are spot on. I don't think I have yet found two equivalent definitions of a Goldberg polyhedron. One would have to go back and read Goldberg's original papers and see how rigorous he was - probably no more so than t...
by guy
Sat Oct 05, 2013 7:08 pm
Forum: Polyhedra
Topic: Groupe Facebook
Replies: 6
Views: 12611

C'est peut-etre une bulle appelé la Langue Anglaise?
by guy
Tue Aug 27, 2013 1:56 pm
Forum: Stella Forum
Topic: Can Anybody Help Me Make A Moravian Star Please?
Replies: 18
Views: 50318

Congratulations.

When can we see the 50-arm star with interior lighting? ;)
by guy
Sun Aug 04, 2013 1:52 pm
Forum: Stella Forum
Topic: Can Anybody Help Me Make A Moravian Star Please?
Replies: 18
Views: 50318

Yes, you are right. I think "rectify" may be the operation of blending the polyhedron with its dual, I can't remember if that is the right word. It certainly gives a more accurate model (and nicer) than truncation. And yes it is augmentation not stellation. There might well be a convex core that can...
by guy
Sat Aug 03, 2013 7:12 pm
Forum: Stella Forum
Topic: Can Anybody Help Me Make A Moravian Star Please?
Replies: 18
Views: 50318

I estimate around 48 points, by: counting all the points in its outline, adding all the visible points within its outline, then assuming that the same number are hidden round the back. So it might well be the 50-point Moravian star - for hints on its construction, see for example http://en.wikipedia...