A few pics

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Robin Adair
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Re: A few pics

Post by Robin Adair » Thu Nov 07, 2019 6:56 pm

Wow! Those are stunning. (Would you be able to post the files?).
Since I’ve just begun making compounds, I haven’t gotten into the fine points of alignment. What I did was to bring the three polyhedrons into a memory slot for each one. My first attempt created one inside of and hiding the other. I realized that I needed to make each a different size, to expose parts of it. I gave each a different color before combining them. I used the mouse to align them, then combined them. When I began to build the model, I realized that I was lucky to get the individual parts aligned as well as they were.
How can I rotate and move the individual parts with better precision than simply spinning them with the mouse? Or is there a better way to do this? I was thinking of taking, say two tetrahedrons, point to point, and “covering” the connection with another polyhedron, perhaps one with holes, showing the connection (just as an example). I haven’t played with the program enough to discover how such things are done

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marcelteun
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Re: A few pics

Post by marcelteun » Fri Nov 08, 2019 11:55 am

Hi Robin,

I am sure you can combine these with Stella by just adding the compounds as described below, but I let Robert answer that, since I am not familiar with Stella.

I uploaded a zip file (temporarily) on my own site with the two models shown:
https://tunnissen.eu/tmp/14_cubes.zip

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robertw
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Re: A few pics

Post by robertw » Sat Nov 09, 2019 5:56 am

You want to combine compounds that already have the same symmetry group, then they should be aligned.

Before putting them into a memory slot, make sure they're all the same scale by setting "Scale->Base Polyhedron Radius" to the same value for each.

Robin Adair
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Re: A few pics

Post by Robin Adair » Sat Nov 09, 2019 5:00 pm

I have to admit a bit of ignorance. What is meant by the term “symmetry group”? Or, the mu variable? I took high school geometry in 1971, but haven’t used it much since. I didn’t get into trigonometry much, and have forgotten it anyhow by now. Is there a book I could use to bring me up to snuff in this field?

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robertw
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Re: A few pics

Post by robertw » Sun Nov 10, 2019 10:56 am

Hi Robin,

I don't know where you saw the "mu" variable.

You can find "Symmetry Group" in the glossary here: https://www.software3d.com/Glossary.php#symgroup
It's just the collection of symmetries that an object has, eg reflection in a plane, or rotation around an axis.

All I meant was to start with models of the same symmetry. You can see the symmetry group of a model in the toolbar
Image
Here we see that the current model has icosahedral symmetry, including reflection.

Previously I suggested combining the compounds of 6 and 8 cubes. These compounds both have octahedral symmetry, so they should combine well.

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marcelteun
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Re: A few pics

Post by marcelteun » Wed Nov 13, 2019 10:11 am

robertw wrote:
Sun Nov 10, 2019 10:56 am
I don't know where you saw the "mu" variable.
That he must have picked up from me. For the compounds with rotational freedom I use the angle mu. I think I use the same Greek letter as in "Symmetry Orbits". For one of the compounds I used 6 | S4xI / C4xI | mu.

Marcelteun

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