Post 9xYI7keAVMfSd5qnGC by categulario@mstdn.mx
(DIR) More posts by categulario@mstdn.mx
(DIR) Post #9xWWFT4mj5qhUfxDCi by federicomena@mstdn.mx
2020-07-27T21:17:55Z
0 likes, 1 repeats
So @categulario nerd-sniped me. If you roll a circle along the outside of an ellipse, what curve is described by the center of the circle?
(DIR) Post #9xWWdQBB9GKBSXMmq8 by restioson@anarchism.space
2020-07-27T21:19:09Z
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@federicomena roll it around as in the edge of the circle is on the edge of the elipse?
(DIR) Post #9xWWdRa1wLnVnu09DM by federicomena@mstdn.mx
2020-07-27T21:22:28Z
0 likes, 1 repeats
@restioson yup.
(DIR) Post #9xWfWphUlIUYAkPp3Y by restioson@anarchism.space
2020-07-27T21:23:44Z
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@federicomena hmm, dumb guess from me but an ellipse? Is that specific enough?
(DIR) Post #9xWfWsH1CC5y9V3Dhg by federicomena@mstdn.mx
2020-07-27T23:02:06Z
0 likes, 1 repeats
@restioson I don't think it is an ellipse; the sum of the distances to from the center of the circle to the foci will change as the circle moves. (I have no idea if it *is* an ellipse with different foci.)
(DIR) Post #9xXsdNNzvSwswhhq6a by jacethechicken@chickenfan.club
2020-07-27T21:29:59Z
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@federicomena @categulario if you trace the center of the circle it's another ellipse, if you trace some non-center point you'd get like a weird slanted spirograph pattern
(DIR) Post #9xXsdPcFdRXRrUOFbE by categulario@mstdn.mx
2020-07-28T13:03:47Z
0 likes, 1 repeats
@jacethechicken @federicomena it turns out it's not! And I have an ellipse that will help you visualize it:Try with a straight line (yes, straight lines are ellipses)
(DIR) Post #9xXsi3hWXesfLF4Wno by Johann150@fosstodon.org
2020-07-27T21:24:16Z
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@federicomena @categulario isn't it just the same ellipse but smaller/larger depending on if the circle is inside/outside of the ellipse?
(DIR) Post #9xXsi50hfpohP13MKu by categulario@mstdn.mx
2020-07-28T13:04:52Z
0 likes, 1 repeats
@Johann150 @federicomena not quite, it doesn't really fit the definition, you know, two centers and a fixed distance.Try with a completely flat ellipse
(DIR) Post #9xXsmuUUDGIiDyHrlo by brunopostle@mastodon.xyz
2020-07-27T22:11:21Z
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@federicomena @categulario it's not an ellipse, CAD tools that try this draw it as a spline. This is the reason it's a bad idea to use actual ellipses in architecture, ovals made up from fixed radius arcs are more amenable.
(DIR) Post #9xXsmuxCUVGlf1inWi by categulario@mstdn.mx
2020-07-28T13:05:44Z
0 likes, 1 repeats
@brunopostle @federicomena we just need better CAD :opensuse:
(DIR) Post #9xYHFXMvekpXoKw4GW by brunopostle@mastodon.xyz
2020-07-27T22:19:51Z
0 likes, 1 repeats
@federicomena @categulario i wrote some notes on dealing with the ellipse problem, but sorry no mathematics:"Hey, ovals are better than ellipses (for buildings)" https://link.medium.com/c4eKXRrnt8"Actually drawing some ovals (that are not ellipses)" https://link.medium.com/d0PC7wEnt8"Drawing complex curves from circular arcs" https://link.medium.com/I93pqvLnt8
(DIR) Post #9xYI7jOt8gqolPh4nw by jacethechicken@chickenfan.club
2020-07-28T16:55:25Z
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@categulario @federicomena wouldn't you get another straight line if you're tracing the center of the circle rolling along a line?
(DIR) Post #9xYI7keAVMfSd5qnGC by categulario@mstdn.mx
2020-07-28T17:49:25Z
0 likes, 1 repeats
@jacethechicken @federicomena the white dashed line is what you get
(DIR) Post #9xYIYrjcGCqWQmKNdI by jacethechicken@chickenfan.club
2020-07-28T17:50:34Z
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@categulario @federicomena oh I see, I was imagining an infinite line
(DIR) Post #9xYIYs0zDcjzIeSFhw by categulario@mstdn.mx
2020-07-28T17:54:32Z
0 likes, 1 repeats
@jacethechicken @federicomena line segment would be more precise