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Posts posted by pleroy

  1. 4 hours ago, IncongruousGoat said:

    Update: It looks like Kerbal Joint Reinforcement was the mod causing the problem. Eh, I can work around not having it by auto-strutting everything to everything else. If it works well enough in stock...

    Thanks for taking the time to find the mod causing the problem.  From reading its description it's clear that it alters the physics, apparently in ways that are incompatible with Principia.  We'll get in touch with @ferram4 to understand more.

  2. On 10/15/2018 at 3:26 AM, IncongruousGoat said:

    I've been running into an odd bug in my current 1.3.1 RSS/RO/RP-1 save. Any vessels farther from Earth than LEO (an absolute boundary is yet to be established) have certain parts offset from where they should be...

    @IncongruousGoat: This is a very bizarre bug, and not one that has been reported before.  My gut feeling is that this is a nasty interaction with some other mod, but these problems are exceedingly difficult to debug.  The thing that is especially strange is that Principia only translates parts, and never rotates them.  So we could be guilty for the engine being off-centre, for instance, but it's harder to see how we would cause the antenna to rotate.

    If you can put your save on dropbox we'll take a look, but don't hold your breath, more likely than not we won't be able to pinpoint the cause.

  3. 7 hours ago, Geligord said:

    The mod says that I have the wrong version of Windows installed (32 instead of 64), although I have the correct version of the windows installed(x64). What to do?

    You need to have (1) a 64-bit processor (2) a 64-bit installation of Windows (3) a 64-bit installation of KSP.  At least one of these prerequisites is missing (I suspect that you have a 32-bit installation of KSP).

  4. 4 hours ago, Clockwork13 said:

    The output of stderr.log is as follows:

    /home/user/.steam/steam/steamapps/common/Kerbal Space Program/KSP.x86_64: symbol lookup error: GameData/Principia/Linux64/principia.so: undefined symbol: _ZNSt3__119__shared_mutex_baseC1Ev

    @Clockwork13: As mentioned in the FAQs, you need version 6.0-2 of libc++.  You must have a rather ancient version to be missing shared_mutex (it was added in the 3.4/3.5 timeframe).

  5. 6 minutes ago, AloE said:


    Do I understand correctly that the TRAPPIST-1 system starts at epoch : "JD2457000.000000000" =  UTC Noon  Monday 2014 December 8 ?

    @AloE: Yes, that's correct.  That's mostly a round number (in JD) that's happens to fall shortly before the first observation of TRAPPIST-1.  We run a fairly complex and expensive optimization to determine orbital elements that match the observed transits, so it's convenient to start a short time before the first observation.  Also, many sources give dates like "7282.80570" where the leading JD245 is omitted.

  6. 20 hours ago, flyby2412 said:

    Does anyone have the file for Principia 1.2.1? I want to run Realism Overhual and Realistic Proggression with Principia, but so far, RP-0 doesn't have a 1.3.1 release as far as i know

    @flyby2412: Cramer, the last version of Principia to support 1.2.2, can be obtained at https://goo.gl/XgRdRP.  No support, no bug fixes, no questions answered.

    This being said, we recommend to use RP-1 with 1.3.1 and the latest Principia.  Other people seem to have been successful with that setup.

  7. On 8/26/2018 at 12:59 AM, AloE said:

    I have not seen this 'fix' posted else where...my TRAPPIST install just never would 'start a new game' even though Principia or SLIPPIST would run  just fine in 1.4.x installed by themselves...

    so I dug into the glog and noticed the error:

    F0825 23:37:01.099138 32236 interface.cpp:765] missing gravity model for Sun

    Ah, thanks a lot for reporting this, @AloE.

    It turns out that while we coordinated with @GregroxMun when he was developing version 0.6.0 of his SLIPPIST-1 mod, we never fixed the link if the FAQs.  So the version that you downloaded (trappist-1 for principia dedekind.zip) was designed for 0.5.x and had plenty of problems, one of which was an incompatibility with Kopernicus that caused the crash that you encountered.

    I have fixed the link in the FAQs to point to trappist-1 for principia δημόκριτος.zip.  I suggest that you download this version and install it instead of what you have at the moment.  It is better in a number of ways, in particular better alignment of the planetary textures, more realistic radius and atmospheres, data suitable for EVE and Scatterer, etc.  (See PR #1856 and #1859 for details.)

    Apologies for the confusion caused by the outdated FAQs.



    23 hours ago, Antstar said:

    So, I gave this a try maybe a year ago. I absolutely loved the concept, but found the maneuver planner pretty darn impossible to use. The slider was rather terrible for some things (the time IIRC) and desperately needed an additional way to just put in a numerical value.

    There was also an issue with interplanetary transfers where I needed to set the integration intervals to like 1m for around planets (the starting one in particular), obviously not needed for interplanetary space, but then when I tried to extend this to see  where I would end up, it would eat 64GB of memory and blue screen the computer.

    The UI has not changed substantially.

    There have been a number of improvements and fixes regarding memory usage, but it's hard to tell if it has anything to do with what you observed: if you don't submit bug reports, there is no guarantee that bugs will get fixed.

  9. We were on vacation, this is a bulk reply to the thread regarding the ephemeris.

    On 7/17/2018 at 10:45 AM, Dolin said:

    In other words, does principia, at any point, neglect the influence of ships on planets and therefore shave off some computations?

    Yes, we neglect the acceleration exerted by vessels on celestials and on other vessels.  It does save a lot of computations.  It's not as small as @Teilnehmer believes, even though the vessels can be 10^15 times lighter than the celestials, because vessels can be very close to each other (so the 1/r^2 factor matters).

    Note that saving the state of the celestials to a file would be much slower than just recomputing the whole thing.  We are able to integrate about 3 million seconds/second, and as @scimas mentioned the file would be huge.  Just say no to disk I/O.

    On 7/27/2018 at 11:36 AM, Dolin said:

    I'm using RSS with a ton of mods and I see a noticeable difference in performance with and without Principia.

    We'd be interested to know more about this.  We have not observed noticeable differences in performance ourselves except at very large warp factors or at very large distance from the Sun.  If you could open an issue on GitHub with details that help reproduce the problem, that would be great.

    On 7/27/2018 at 2:01 PM, Johould said:

    That's the ephemeris occasionally mentioned in the changelog. I don't know the exact time range or storage, but the motion of celestials is precomputed.

    Right.  The ephemeris is used to (lazily) compute the trajectories of the celestials, and the trajectories of the vessels are then computed in the resulting gravitational field.

    On 7/27/2018 at 9:40 PM, scimas said:

    I'm not completely sure about this, but I think I remember it mentioned sometime that celestials do ignore vessel influence. Although I can't think why that would be; you are anyway computing the force on a vessel due to a celestial, the force on the celestial is just the negative of the one on the vessel..

    That would defeat the purpose of the ephemeris, which is to determine once and for all the gravitational field in time and space, and then to integrate the vessels in that field.  So the two forces that you mention are computed in two completely separate steps, and possibly at different points in time.  As an implementation detail, the mass of the vessels is taken to be exactly 0 in the ephemeris so the forces are not helpful, what we need are the accelerations.

    On 7/27/2018 at 9:51 PM, Johould said:

    Huh, where do interpolation schemes come in? Is that just interpolation within a single time step? Sets of coefficients for polynomial interpretation is how NASA releases projected positions in the real solar system, I thought they were a bit more related.

    To be a bit more specific (for RSS):

    • we start from the positions and velocities, derived from JPL data, for all the celestials at a fixed point in time (1950-01-01);
    • we integrate this configuration forward in time with a Quinlan-Tremaine symmetric linear multistep 12th order integrator and a time step of 10 minutes;
    • for each celestial, we compute polynomials of degree between 3 and 15 to approximate the positions and velocities over 8 points (80 minutes) to 1 mm; these polynomials are constructed in the Чебышёв basis for accuracy and evaluated in the monomial basis for performance;
    • when we need to compute the trajectory of a vessel, we use these interpolating polynomials to compute the position of each celestial.
  10. 10 hours ago, DocRockwell said:

    Is the bug that caused crashes when you had several gravity assists on one flight path fixed? My campaign's been stalled at 1977 with several probes launched onto a grand tour.

    Dunno, did you report it on GitHub?  We fixed two bugs that could match that description (see the change log) but it's hard to know for sure.

    10 hours ago, DocRockwell said:

    Can RSS Expansion (https://github.com/PhineasFreak/RSSExpansion) be added to an ongoing save game?

    Nope, the solar system is constructed when you start a new game.

  11. 25 minutes ago, scimas said:

    @eggrobin The change log says "this version supports 1.3.1 and 1.4.x," does that mean I can use it with 1.4.3 too, or only 1.4.4? Also, the topic title is still showing "[1.3.1, 1.4.3]."

    I tested it with 1.4.3.  It works fine.  Not tested with older releases 1.4.x but should be ok.

  12. 1 hour ago, hypervelocity said:

    @eggrobin - I have never used a Planet Pack before with RSS - in regards of the mini-mod for TRAPPIST-1, what are the installation instructions? Should I install GregroxMun's mod and everything will work automagically?

    Use the FAQs, Luke!  The FAQs have instructions for installing "Trappist-1 for Principia".

    Two caveats, though:

    1. Our mini-mod is on top of GregroxMun's mod, not on top of RSS, so it's incompatible with RSS (you cannot be in two solar systems at the same time, right?).
    2. If you are using 1.4.3 there's a glitch and it will fail to load because of an incompatibility with Kopernicus.  Give us a few days to update the .zip file.
  13. 20 hours ago, Zeiss Ikon said:

    Am I missing something?  Is there in fact a binary download available for Cramer, Ubuntu 64-bit, KSP 1.2.2 version (and if so, why isn't it linked from the start of this thread)?

    Thanks to @scimas for the reply.

    Public service announcement: the links to the releases are in the README.md file on GitHub.  By looking at the history of this file, it's easy to find previous versions of the mod.

  14. 1 hour ago, Delay said:

    Not sure if Kopernicus automatically means this, @pleroy might answer that better, but if you're using the stock system with slight modifications you'd have to modify the Jool system yourself. Principia changes the otherwise very unstable system to make it (at least somewhat) stable, but as soon as the system is modified Principia won't add its modifications to the system.

    @Delay is right: if using Kopernicus, you want to look at this section of our FAQs.

  15. On 4/30/2018 at 9:59 PM, msnbcorp said:

    I think that as principia is dedicated to real physics and made external calculation continuously, it should be a good idea to implement it directly in this mods ...

    Future release idea may be ? 

    It has not escaped our notice that the specific physics computations we have implemented immediately suggest a possible extension to support angular momentum conservations.  As a matter of fact, quite a few of the classes that manage parts, vessels and pile-ups were designed with this in mind: "if, in addition to position and speed, we also had rotation and angular momentum, then it would still work because...".  We just never got to implement it.  A bit of design will be required, but I think that the foundation is sound.

  16. @AlliedForth @hypervelocity @scimas: I have added some words to the FAQ but basically reusing a save that was not created with Principia will have strange results because the celestials will be in different places.  It should not crash, but it may or may not be what you expect.

    This is unrelated btw to the notion of adding new vessels: vessels get created and removed all the time as part of normal gameplay (e.g. when stages separate or when a rendezvous happens) so this is something that we have to handle properly. 

  17. 23 minutes ago, Banshee said:

    It's claimed that there are installation instructions in the FAQ; this does not appear to be the case.

    I guess we can never be too explicit: unzip the archive and copy the Principia folder into the GameData folder.

    25 minutes ago, Banshee said:

    What is the installation procedure for Principia? I have heard it is more involved than simply dropping the folder into GameData.

    You heard wrong.  I am curious to know where this rumour comes from, though.

  18. On 21/03/2018 at 2:03 PM, ButchFlowers said:

    Quick question, I am just running a stock system (v1.3.1), and I'm planning on using some visual overhaul mods that use Kopernicus (e.g. think Spectra, KSPRC). Will the Jool system remain stable if use these mods? Or does stock Kopernicus override Principia's planet configs?

    This is documented in the FAQs here.

    On 29/03/2018 at 2:22 AM, njbrown09 said:

    @eggrobin how did you manage to do axial tilt? Is it possible you could make a mod just for axial tilt (or guide me to the code where you have it in principia so i can make it myself)

    We do axial tilt by tilting the universe.  The current main body must always have its axis vertical as seen by the game, otherwise the terrain system and other entertaining things break.  This fundamentally requires a plugin capable of tracking the orbits in a fixed reference frame in order to be able to represent them in the tilted universe.  This means that this plugin would have its own model of where every vessel is located and would have to evolve the orbits itself.  At this point the plugin owns all the physics and is essentially Principia.  (Principia without n-body gravitation would be as hard to develop/maintain and much less interesting to us.)

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