Help with Colours

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Peter Kane
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Help with Colours

Post by Peter Kane » Fri Aug 27, 2010 3:56 pm

I'm trying to work out the colour scheme (map) for the great ditrigonal dodecicosidodecahedron (MW 81). I tried viewing the model in Stella after selecting the colour scheme that matches the one used in Wenninger's book, and noting positions as the model is rotated, but I'm red-green colour-blind and I have real difficulty tracking the colours, which seem to change as the model rotates (due to the lighting effect).

MW describes how to complete the first decagram, and its easy enought to work out the positions of faces that sit around the adjoining edges of adjoining decagrams (as these complete the vertices of triangular faces that appear around the edges of the first decagram), but I can't work out the rest.

Is there a way to obtain this information using Stella ?

Tia,

Pete K
PS I cant type either !

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Peter Kane
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Post by Peter Kane » Fri Aug 27, 2010 5:48 pm

You idiot ! It is obvious !

Ah well, I see it now: the 5-colour arrangement for the triangular faces, just as MW said. The decagons have their own set of (six) colours. Fool.

Anyway, I found a way to map the colours: create a series of images in photoshop, consisting of the same digit or letter repeated to fill the image (eg, a grid of ones for the 1st image, twos for the second etc). Then get Stella to load the image to all faces of the same colour. I'm sure there's a simpler way, though.

pete K

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oxenholme
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Post by oxenholme » Sat Aug 28, 2010 7:45 pm

I must admit I'd be tempted to use ten colours for the triangles and six colours for the decagrams and pentagons.

Keep us posted on progress and post a picture or two when you've completed it.

I've currently got my eye on a stellation of the icosahedron with chiral tetrahedral symmetry that appears like a sort of distorted deltahedron.

I'll post a picture when I've made it.

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Peter Kane
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Post by Peter Kane » Sun Aug 29, 2010 9:08 am

I'm having 2nd (actually about 22nd) thoughts about this one, having made several mistakes:

- Not fully understanding the colour scheme. MW suggests 6 & 5 colours (i.e 5+1 and the same five). Previously, used this for the small ditrigonal icosidodecahedron (MW81) and it works reasonably well, so I thought it would also work here. Having made a start, I’m not so sure; I think it might look a bit messy. Perhaps 5 + 1 or 5 + 6 with patterned card might be better.

- Choosing the wrong card. Bought some caustic art card. The colours are great and its reasonably thin, but it is difficult to work with and cracks easily with the severe folds that are required with this model. Also, its beautifully shiny finish marks as soon as you look at it.

- Using the wrong number of tabs. The decagrams look better with no tabs on them.

I haven’t decided whether to start afresh or persevere a bit longer. Some time ago, I nearly abandoned an attempt at the great stellated dodecahedron using quite heavy card with a metallic finish. I had to swap to water-based glue there as the UHU ate the finish. I also had to more to single tabs. Originally, the dimples had ugly holes in them but I found that a wad of tissue paper soaked in PVA glue held the vertices really well when dry. Also, the card was so shiny, I thought reflections might be a real problem. I persevered and the results were quite stunning (well, for me).

Anyway, thanks for the suggestion. I look forward to seeing the next of your chirals.
Pete K

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oxenholme
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Post by oxenholme » Sun Aug 29, 2010 10:20 am

I bought twenty nine different colours of card, so I have enough choice for most models.

Like you I'm red-green colour blind, so I have to write on each sheet of card what colour it is.

I can handle 5 colours for hexecontahedra and 4 colours for icositetrahedra, but for triacontahedra I normally use 15, for dodecahedra I use 6, and for Icosahedra I use 10.

Oh well, back to cutting out and sticking...

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oxenholme
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Post by oxenholme » Thu Dec 30, 2010 6:43 pm

I'm about 40% of the way through a stellation of the "degenerate" with the great dodecahedron edge inscribed in its icosahedron shell.

I'm using 16 colours - 6 easily distinguished colours for the dodecahedral faces and 10 far less identifiable colours for the icosahedral.

I selected the colours in daylight and they seemed manageable, but in fluorescent electric light it's a different matter! I cannot tell pale blue, pale green and pale pink apart and have to hold each sheet against the model so far and try to decide whether I've got the right colour.

Added to which the polyhedron is proving to be less than easy to make.

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