Faceting

The place to talk about Stella4D, Great Stella, and Small Stella. Feel free to ask questions about them here.
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Rosemary Lyndall Wemm
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Faceting

Post by Rosemary Lyndall Wemm » Thu Jun 15, 2017 7:23 pm

I cannot understand the instructions for faceting.

1. How do you make a flat slice across a face?

After I have chosen the vertices (by Shift-Left Click) when I press the UpArrow I get anything but a flat face. How do I make a flat slice across the model at the selected vertices?

2. What if I want to make a facet (flat surface) using points along the edges that are midway between vertices? How do I do that?

ndl
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Faceting

Post by ndl » Thu Jun 22, 2017 5:07 am

I am somewhat new to Stella but I hope I can help.
Facetting works in 2 ways, having the program choose facets or creating them yourself. If you want to create your own facets by selecting vertices you would then Shift-right-click to accept that facet, not use the up arrow (that's for program choosing it's own facets or facettings depending on what you select in menu).
Now, you're going to want to change the symmetry to "C1" if you just want a single slice through a polyhedron, then you could add the outer faces on one side manually.
For your second issue, there's a menu option in "Poly" to subdivide faces, maybe that's what you are looking for.
Hope this was helpful to you.

Rosemary Lyndall Wemm
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Re: Faceting

Post by Rosemary Lyndall Wemm » Fri Jun 23, 2017 3:30 am

[quote="ndl"
- -there's a menu option in "Poly" to subdivide faces,- - -
]If you want to create your own facets by selecting vertices you would then Shift-right-click to accept that facet, - - -
Now, you're going to want to change the symmetry to "C1" if you just want a single slice through a polyhedron, then you could add the outer faces on one side manually.- - -


Thank you. It partially helped.

I found the Subdivide Faces option on the Poly menu. I figured out that I needed to set the Options to 2, which worked for the first model I tried (a model with faces that had 4 sides), but found that I had to change this to 5 or models with 5 sides.

I tried pressing Shift Right Button, and got nothing until I realized that I had to do this on the other screen which had to be set to the Preview Faceting selection. I finally found the Menu that provided this option.

I could not, however, find any Menu that allowed me to change the Symmetry to C1. Could you explain how I do that?

ndl
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Location: Queens, NY

Post by ndl » Fri Jun 23, 2017 2:47 pm

Yes on the right side above the pane there is a colored drop down menu that sets the symmetry, it's a list of possible symmetries for that polyhedron. I'm not sure I understand all of them but c1 means no symmetry.

Rosemary Lyndall Wemm
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Post by Rosemary Lyndall Wemm » Fri Jun 23, 2017 6:02 pm

I cannot find a way to upload an image stored on my computer so I cannot provide a screenshot of the problem. Words are a very poor method of trying to explain a visual matter, but I will try.
I use Shift-Left Click and the "..."to define a facet. This shows up on the View-Facets window as a plane in the right place.
When I press Shift-Right Click the plane disappears.
When I press any combination that is supposed to make this plane into a permanent feature or facet it, then I get messages telling me that the facet is incomplete or I get a highly complicated picture with multiple new planes and facets all over the model.
I have tried every menu and button that I can find. Nothing works as it is advertised to work.

An additional problem is that pressing F1 or going to the help Menu and pressing the button for the Great Stella Manual gets zero response. Perhaps the program did not install itself properly on my computer. I have no idea what the problem is, or how to fix it.

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Ulrich
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Post by Ulrich » Sun Jun 25, 2017 9:38 am

You cannot upload pictures in this forum directly, you have to put a link to a file you uploaded to your website or to photobucket or something like that.
Before creating a new model from facetings make sure that you chose a layout with at least 2 windows (hit ctrl+2). Then you have the base model in the left one. In the right one you activate the faceting preview (little yellow/green symbol, 6th from the left side). Then you show the vertices by hitting "v". You see white points where the vertices are in both windows. You can increase their number by subdividing the faces ("Poly"-menu). Now you go to the faceting mode (little white triangle, 5th from the left), keep the "shift"-key pressed, select the vertices of your new facet by left-click and accept it by right-click (shift always pressed). In the right window you see the new facet with green edges. To complete the model you have to connect these green edges by creating a new facet. If everything is ok you see the message "faceting is complete!" in the left upper corner of the right window. Now you hit ctrl+shift+f to create the new polyhedron which appears in the left window. In the right one you just see the vertices of it.
The stella 4d manual is online, see: http://www.software3d.com/StellaManual.php

Ulrich

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robertw
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Post by robertw » Sun Jul 09, 2017 8:29 am

The word faceting has a specific meaning in the world of polyhedra. A faceting is a new polyhedron that shares the same set of vertices as the original. Strictly, it shouldn't have any additional vertices. This may not be quite sufficient for you if you wish to cut a polyhedron with some plane, unless the plane only intersects edges at their ends, ie at the vertices. Otherwise it would need to introduce new vertices, which it doesn't do. But as ndl pointed out, you can subdivide the polyhedron first to introduce more vertices.

Everything should work as advertised, but some of the advertising may be quite oblique at first. To build up a faceting, you should do as Ulrich suggests and have two views, one with the original model and one with the faceting preview.

Each facet is created using Shift+Left-click on each vertex, and then Shift+Right-click to let Stella know you've finished. This then becomes a complete facet, but it is not yet a complete faceting (not a complete polyhedron). Stella will only accept it when all edges are matched to other faces. You can't have a free-floating face. In the faceting preview window, invalid edges are highlighted in one of a few colours, mainly green for unmatched edges. Only when all edges are matched can you turn this preview into a real model, using Ctrl+Shift+F ("Faceting->Create Faceted Polyhedron" from the menu).

So, "messages telling me that the facet is incomplete" is when not all the edges are matched up. And "multiple new planes and facets all over the model" is probably because you're using full symmetry. The idea of faceting is that whatever facet you create gets repeated symmetrically, so if you only want one, then you need to drop to a low symmetry as ndl mentioned.

There's no simple way currently to simply cut a polyhedron along a plane. Faceting can help, but you have to create not just the shape of the slice, but also all the other faces you want to keep. You can use Ctrl+Right-click to speed this up though. Just aim it at any original face that you want to keep in its entirety to create a new facet from it without having to click on each vertex around it.

I don't know why F1 doesn't work. It looks for the manual in the same folder as the EXE, so if you copied the EXE to another folder after installation, then that would explain it. You may have done this by accident when trying to make a shortcut to it.

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