Message #1179

From: Melinda Green <melinda@superliminal.com>
Subject: Re: [MC4D] Re: Tetrahedral prism {3,3}x{}, 3 layers solved
Date: Tue, 28 Sep 2010 14:24:29 -0700

I’m glad that you guys are having fun with the tetrahedral prisms but
I have to remind everyone that solutions to puzzles not included in the
menu must be considered as unofficial results, at least for ones that
are not trivial extensions to ones already there. Not all twists that
should be allowed on this puzzle are currently allowed, making it on one
hand harder to solve, but on the other hand, the scrambling may not
reach all possible positions, making it potentially easier to solve. I
think that we’ll have to consider any firsts or shortests as tentative
at best. Please do continue to explore experimental puzzles because this
is a great way to help us figure out how they should work. Just remember
that any such solutions are unofficial until they are added to the menu
of supported puzzles.

-Melinda

On 9/28/2010 9:52 AM, Roice Nelson wrote:
>
>
> Hi Andrey and Nan,
> Cool to hear about your adventures with the tetrahedral prism
> puzzles. The reason the {3,3}x{} puzzles aren’t in the UI is that
> there were known problems with them, as you’ve found. Plus, we had to
> leave some items for future releases :) I dug up the development
> emails we were exchanging last year to refresh my memory, and am
> including a few relevant portions below.
> on 11/11/09, roice wrote:
>
> So… we have coded a possible change in the sticker twisting
> behavior and are curious of your thoughts compared to the current
> behavior you just tested. The candidate behavior is that all 2C
> pieces only do "face center" twists, all 3C pieces only do "edge"
> twists, and all 4C pieces "corner" twists. 1C pieces wouldn’t
> twist anything at all. So 2C pieces that are very close to a
> corner would no longer do a corner twist. This change also would
> correct the behavior you noted on the length-7 dodecahedral prism.
>
> on 11/11/09, roice wrote:
>
> However, I already happened to run into an interesting downside
> behavior with the change. I got the tetrahedral prism puzzles
> working tonight, but held off enabling in the UI just yet because
> of the following. Similar to David’s observation of how the
> length-2 simplex puzzle has a 5C piece, the length-2 and length-3
> tetrahedral prism puzzles have a number of stickers which should
> twist like 2C pieces, but actually are part of 4C pieces. So the
> wrong grips get considered, and the end result is some twists
> which we want are being disallowed. The puzzles are therefore
> unduly limited. In fact, on the length-2 puzzle, the end result
> is that only the two tetrahedral faces can be twisted, and the
> current scrambling code goes into an infinite loop because it
> doesn’t like the lack of variance there.
>
> In short, MC4D currently uses a "piece type" property (2C/3C/4C) to
> help control twist types. This is mostly good, but number-of-colors
> turns out to not be a discriminating enough property in all situations
> (in particular, on the tetrahedral prisms). The problem of matching
> up pieces with twist types is a difficult one to find an elegant
> general solution for. When this is worked out and these puzzles are
> officially released, they will likely have slightly different
> twisting behavior.
> I think it’d be nice to change the relative sizes of the tetrahedra
> and prism portions on these puzzles as well. Unlike other polytopes
> which are constrained to have fixed cell sizes, prisms have some extra
> flexibility there…
> Take Care,
> Roice
>
> On Tue, Sep 28, 2010 at 10:17 AM, schuma <mananself@gmail.com
> <mailto:mananself@gmail.com>> wrote:
>
> Congratulations! Nice work!
>
> Yesterday after seeing you mentioned {3,3}x{}, I tried the 2-layer
> version immediately. For the 2-layer version, any automatic
> scramble freezes the program. So I have to manually scramble it.
> But all allowed scrambles are always trivial to solve.
>
> Then I went on to see the 3-layer version. I found it not easy and
> I didn’t that ctrl-f work for this version. I should give it a try
> soon.
>
> Nan
>
> — In 4D_Cubing@yahoogroups.com
> <mailto:4D_Cubing@yahoogroups.com>, "Andrey" <andreyastrelin@…>
> wrote:
> >
> > It’s strange that one of the smallest 4D puzzles is not listed
> inMC4D puzzle list, so you have to generate it by "Invent my own"
> command (with line "{3,3}x{} 3").
> > It took some time to find the most convenient views of the
> puzzle (view with two tetrahedrons has very different "shrink
> face" value than view with 4 prisms). You can’t rotate prism to
> 120 deg, so use sequence of two 180-deg turns instead. Not very
> easy…
> > I started with sorting of pieces - top, middle and lower
> layers (like the solver who plays with 3^3 first time - build one
> single-color face :) ). Then there was orientation of middle layer
> pieces and then combining of 3rd layers parallel to prisms (just
> 3-cubie segments) with adjacent cubies. Next step was to put all
> corners in their place - and there were first two problems.
> > First, middle layer was upside-down - and I had to flip all
> its pieces and save colors of top and bottom faces.
> > Second, in the end of this stage I found one corner piece
> (pair of pieces, really) with wrong orientation! It is normal for
> pyraminx, but here you have to think how it can be :)
> > When all corners ans 3Cs of middle layer were in place I found
> myself with 3 parallel pyraminxs and with the task to put all
> their 2Cs in place.
> > One operation was enough for it… well, almost enough. At
> first I tried to move cubies to places in proper orientation, but
> soon found that I can’t remember setup twists that contain of
> pairs of prism flips… So I decided to position pieces first.
> > Solving of 3 pyraminxs with the same sequence of 3-cycles went
> smoothly… until there were two transpositions on opposite faces
> (parity problem?). When I solved it there was one wrong oriented
> cubie on top side (and 3 on bottom) - but this time I could
> remember setup twist ))) So when I twisted 3 sets of 2 cubies,
> puzzle was almost solved.
> > So this one is solvable from the scratch, without operations
> development. It doesn’t beat {3}x{3},3 :)
> >
> > Andrey
> >
>
>
>
>
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