raptop changed the topic of #principia to: READ THE FAQ: http://goo.gl/gMZF9H; The current version is Fréchet. We currently target 1.5.1, 1.6.1, and 1.7.x. <scott_manley> anyone that doubts the wisdom of retrograde bop needs to get the hell out | https://xkcd.com/323/ | <egg> calculating the influence of lamont on Pluto is a bit silly… | <egg> also 4e16 m * 2^-52 is uncomfortably large
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Gregrox. — psst I thought principia folks might get a kick out of this
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saltedfish. — How do you solve the probe's orbit in principia? I think the probe doesn't influence orbit of planets. So it isn't necessary to solve orbit of planets every time when probe's velocity changes. But when I use numerical methods to solve orbit of planets, I will get some points in phase space. Then I try to solve the probe's orbit. I need the orbit of planets in phase space as a function of time,
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saltedfish. — These issues came out when I try to make a orbit calculator, just like principia. I want to figure out these issues. Thanks.
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RurouniDonut. — You’re trying to make an orbit calculator?
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RurouniDonut. — Thats awesome
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saltedfish. — Yes. In fact I have already made an orbit calculator to do some calculation that doesn't need very high precision. I used spline method as the interpolation method. But when I learned computational physics, I realized spline method can't hold the algebraic precision.And the Lagrange method(high order polynomial interpolation) have runge phenomenon that the error may tend to infinity. So I have
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RurouniDonut. — I wish I could do that stuff D:
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egg. — @saltedfish the integrations of the planetary ephemerides and that of the vessel are separate; the ephemerides are interpolated
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egg. — standard interpolation techniques can be looked up, typically it's Чебышёв series
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saltedfish. — Thanks. I will read the paper.
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egg. — we even use interpolation after than when manipulating & plotting the trajectories of the vessels, to downsample them
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egg. — we compute them at a resolution far higher than what is needed to draw them, so we drop points (checking that the cubic Hermite spline remains close enough to the dropped points as we do so)
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saltedfish. — So you choose the Chebyshev polynomials as the basis vector in Hilbert space, use the least-squares fit to find coefficients. The granule length and polynomial degree just use the data in the paper.To fit orbits of planets.
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saltedfish. — And use cubic Hermite spline to draw the orbit
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saltedfish. — is that right?
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egg. — and in practice while we compute the polynomials in the Чебышёв basis, we then transform them to the monomial basis and Estrin-evaluate them for faster evaluation
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egg. — because evaluating those polynomials is performance-critical when integrating the ships
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egg. — the cubic Hermite splines are only for the ships, not for the planets
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egg. — since we already have polynomials for the planets, we don't need to reinvent a polynomial
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saltedfish. — I understand. Thank you very much.
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[Principia] pleroy opened pull request #2434: Run the adapter in the main menu to detect loading problems early - https://git.io/JejU3
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[Principia] pleroy synchronize pull request #2434: Run the adapter in the main menu to detect loading problems early - https://git.io/JejU3
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[Principia] pleroy commented on pull request #2434: Run the adapter in the main menu to detect loading problems early - https://git.io/JejUE
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[Principia] eggrobin labeled pull request #2434: Run the adapter in the main menu to detect loading problems early - https://git.io/JejU3
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[Principia] pleroy closed issue #2385: Check for the C++ redistributable in the main menu - https://git.io/Je1X3
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[Principia] pleroy pushed 3 commits to master [+0/-0/±3] https://git.io/JejTv
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[Principia] pleroy ff859b9 - Run the adapter in the main menu to detect loading problems early.
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[Principia] pleroy 73eeca0 - Merge pull request #2434 from pleroy/2385 Run the adapter in the main menu to detect loading problems early
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[Principia] pleroy closed pull request #2434: Run the adapter in the main menu to detect loading problems early - https://git.io/JejU3
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neph. — @principia team you should rename the toolbar icon from .png to .truecolor (both pngs, but .truecolor exempts it from compression so Squad won't make your toolbar icon all blurry if somebody's running with half size textures)
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just make sure your icons aren't 8192x8192 uncompressed
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Butcher. — Principia needs a slick icon.