Angles of edges

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boomfiziks
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Angles of edges

Post by boomfiziks » Sun Jun 24, 2012 3:40 am

Hello. I am new to using Stella 4D. One of the main reasons I got the program was to help me to create wooden models of the shapes. I do a fair amount of segmented woodturning and a lot of the segments are flat and the edges (where the wood meet to create the circle) are mitered to create a circular shape. It's pretty easy to figure out the angles, just dividing the number of segments by 360.

What I would like to see is a display of each angle of the face of the shapes AND the angle of the edges so that they when I glue them together, they are mitered to the correct angle.

I've recently discovered the ability to stretch/squash the shapes and this has given me the idea of making some very unique woodturnings. The problem is, figuring out all of the angles would be a nightmare for a stretched/squashed polyhedron (using the non-uniform scaling).

I'm not sure if this feature is already available. If so, could someone direct me of where I could find it? If not, is there a way to figure it out on the Stella 4D software?

Thank you for your time,
Dwight

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robertw
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Post by robertw » Sun Jun 24, 2012 5:32 am

Is this what you want?

Image

You can see this by using "Display->Show Vertex Angles" and then selecting a vertex with Ctrl+Right-click. The yellow angles are what you want, if I've followed what you're asking. These are the angles of the faces surrounding a vertex once flattened onto a single plane.

Rob.

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Post by robertw » Sun Jun 24, 2012 5:50 am

Actually, that's for angles around a vertex. You might also be interested in "Nets->Show Edge Data->Dihedral Angles" and "Nets->Show Edge Data->Mitre Angles". You need a flattened or folding net view open to see the result. It shows the angles on each edge.

There was debate at some point about which angle should be referred to as the mitre angle, so see if you agree with what it gives. I don't do any woodwork, so I can only go by what others say.

Actually, further to that, maybe you'd be interested in making a YouTube video or two yourself about using Stella for woodwork? It's one thing I won't be able to do!

Thanks,
Rob.

boomfiziks
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Post by boomfiziks » Sun Jun 24, 2012 12:10 pm

Thank you for the information. That's really helpful. When I start making some wooden objects, I'll post pictures and/or videos of the process. It may be a little while as we are expecting our first child in the next couple of weeks...a lot of my hobbies have been put on the back burner. :-)

Regarding the terminology of miter vs bevel. It can get confusing. Here's a video about a miter saw. It is an advertisement, but it goes over the terms of miter vs. bevel. http://www.youtube.com/watch?v=I10K3N-U ... ata_player
Essentially, a miter is the angle of cut relative to the fence. The bevel is the tilt of the blade. So for an example, if you have trim around around a doorway, chances are it has a miter of 45 degrees and a 90 degree bevel.

If you have a picture frame that has a 45 miter and 45 bevel cut. The miter creates the perimeter around the picture. The bevel would cause the frame to "flare out". Here's another link that shows a diagram on a piece of wood. http://jansson.us/jcompound.html

So for your polyhedrons. Let's say each face is a pentagon. To cut a flat pentagon, you would be making a miter cut of 36 degrees. If I left the blade vertical (90 degree bevel), then I'd just have a bunch of pentagons making a flat pattern. To make it more spherical (a polyhedron), I would have to make a bevel cut.

I haven't looked at the program yet, but from what you've told me, I think what is called a miter cut would actually be a bevel cut. Though, I guess it could also be argued that if you rotate the piece of wood, a bevel cut could be a miter cut. So who knows..... :-)

I hope this information helps to clarify the terms.

Have a great day,
Dwight

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robertw
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Post by robertw » Sun Jun 24, 2012 1:12 pm

The mitre angles in Stella are calculate as follows from the dihedral angle:

mitre = 90 - (dihedral / 2)

The "/2" is because we want each wooden face to make up half the dihedral angle where they meet at an edge.

The "90 -" depends on the definition of mitre versus bevel.

Do you think this should be called bevel angle instead?

Rob.

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