Axial Tilts

[SAS123]

With KSP having come so far and with so many new updates and that, i was just wondering. If or When will Axial Tilts be added to planets? I mean i don't know that much about the coding behind it but i would assume it wouldn't be too hard to code. Add the degrees of tilt and the starting rotation of that tilt(Like if the north pole is facing away or towards the sun at a particular position in the orbit.)

[IncongruousGoat]

Not in the foreseeable future (i.e. never). Due to the way planets are modeled, they can't have any axial tilt other than zero. It turns out to be surprisingly hard to code, and would require rewrites of some pretty deep parts of the code base. I can't give more details than that, not being familiar with the internals of KSP's code base. This idea has been around for, well, as long as anyone can remember, and every time the response is the same. Sorry to disappoint.

[klesh]

Here is a thread where this topic came up in January.  In it are links to ~10 or more threads discussing axial tilt over the years, including some (now gone) developer's input.

 

 

[Red Iron Crown]

17 hours ago, IncongruousGoat said:

Due to the way planets are modeled, they can't have any axial tilt other than zero.

I think you mean to say: Axial tilt is always exactly equal to inclination. Any body in an inclined orbit in KSP has non-zero axial tilt.

That said, my understanding is that an incredible amount of KSP's code is written under the assumption that all celestial bodies' axes point in the same direction. Reworking this would require a substantial rework of the whole system, which I would consider very unlikely at this stage of the game's development.

The developer of Principia has been working on a workaround for this, by tilting the rest of the universe when entering a body's sphere of influence. There's a working prototype IIRC, but it has some side effects. Maybe we'll see a mod solution for this, who knows?

[Superfluous J]

4 minutes ago, Red Iron Crown said:

Axial tilt is always exactly equal to inclination. Any body in an inclined orbit in KSP has non-zero axial tilt.

It is? I haven't checked in a (long) while and no planet in KSP is in an orbit tilted enough to stand out, but I always thought all north poles were tangential to each other regardless of orbit tilt.

Also, doesn't RSS use this fact to "fake" Earth's tilt? If axial tilt followed orbital tilt, tilting the entire solar system 23 degrees would just cause Kerbin to tilt alongside it.

[IronCretin]

I think he means axial tilt relative to the orbital plane, in which case he's technically correct.

[Superfluous J]

22 minutes ago, IronCretin said:

I think he means axial tilt relative to the orbital plane, in which case he's technically correct.

Aha. We said the same thing in different ways.

Though FWIW I don't think anybody who wants "axial tilt" wants anything other than "axial tilt independent of orbital tilt."

[IronCretin]

I agree with you, I'm just being a pedantic nitpicker.

[OHara]

1 hour ago, 5thHorseman said:

Though FWIW I don't think anybody who wants "axial tilt" wants anything other than "axial tilt independent of orbital tilt."

I do. Axial tilt of Kerbin's rotation axis relative to its orbit (the nit-picky definition) is the interesting part of the tilt.  It gives seasons, and makes launches to other planets a bit more interesting.  It was still worth implementing in the 'Real Solar System' mod by tilting the orbit, rather than the rotation axis.

I have been tempted to try re-configuring the orbits following the very good suggestion from guigui30000 linked above (following a couple levels of links) and wonder if can be done through edits or Module Manager following RealSolarSystem.cfg as a guide.

[Superfluous J]

5 hours ago, OHara said:

I do.

Well then that's what you have now, so you're all good

I still want Kerbin and Eve to be roughly co-planar, but Eve rotate backwards like Venus does. I'd also like Gas Giant 2 to be tilted like Uranus, and think it's not really worth doing a GG2 without something that drastic to differentiate it from Jool. That - to me - is the interesting part of tilt.

[Red Iron Crown]

11 hours ago, 5thHorseman said:

It is? I haven't checked in a (long) while and no planet in KSP is in an orbit tilted enough to stand out, but I always thought all north poles were tangential to each other regardless of orbit tilt.

All poles are parallel, yes.

11 hours ago, 5thHorseman said:

Also, doesn't RSS use this fact to "fake" Earth's tilt? If axial tilt followed orbital tilt, tilting the entire solar system 23 degrees would just cause Kerbin to tilt alongside it.

Axial tilt is always relative to the orbital plane. RSS tilts the whole system to get Earth's tilt correct, the other planets are not correct.

10 hours ago, IronCretin said:

I think he means axial tilt relative to the orbital plane, in which case he's technically correct.

The best kind of correct.

10 hours ago, 5thHorseman said:

Aha. We said the same thing in different ways.

Though FWIW I don't think anybody who wants "axial tilt" wants anything other than "axial tilt independent of orbital tilt."

Agreed, it would be a great feature. I think the payoff vs work invested to implement it is rather low, however.

[Superfluous J]

54 minutes ago, Red Iron Crown said:

I think the payoff vs work invested to implement it is rather low, however.

I agree with this, but only because I think the work investment is so high. I think the payoff would be - pun slightly intended - revolutionary.

[Nicias]

Would it be possible to have a planet that rotates retrograde?

 

[OrbitalBuzzsaw]

One word - No.

[OHara]

6 hours ago, Nicias said:

Would it be possible to have a planet that rotates retrograde?

Real Solar System makes Venus rotate retrograde by giving it a negative 'rotationPeriod'. The 'north' pole is in the same direction as the other planets' north poles, due to the fixed orientation of the poles in KSP, making the sun rise in the west in RSS Venus -- same as for the real Venus using the convention NASA chose to orient Venus's 'North' generally along ours.

It looks like each of RSS and Kopernicus have code in their .dll s to read such values from configuration files, so at least that amount of code seems necessary to un-align Kerbin's orbit- and rotation- axes.

[Waxing_Kibbous]

I can't help but think the current code is needlessly complex if it can't be done as things stand today. If the planet meshes were bound to bones and the bones were set to follow a path (the orbit) you could do all sorts of rotational things, tilt, spin, wobble, with very simple spline manipulation- it's pretty basic rigging, and I have to think Unity supports it. Maybe the new team members will look into this...

Edit: Just did some quick searching, I may be wrong in my assumptions. Meh

Edited December 23, 2016 by Waxing_Kibbous

[Red Iron Crown]

2 hours ago, Waxing_Kibbous said:

I can't help but think the current code is needlessly complex if it can't be done as things stand today.

Too simple, not too complex. The coordinate systems for all the frames of reference assume North is always the same, and all the math built upon the coordinate systems (which is a *lot*) assumes it, too. It would be a monumental task to refactor the code at this point.

 

[omelaw]

 

5 hours ago, Red Iron Crown said:

Too simple, not too complex. The coordinate systems for all the frames of reference assume North is always the same, and all the math built upon the coordinate systems (which is a *lot*) assumes it, too. It would be a monumental task to refactor the code at this point.

 

make a damper planet at a planet's desired orbit and make a real planet orbit around damper planet at near zero (like, 10^-4m) range and inclination of whatever we want?

I'm sure KSP will hate it.. what happens if we makes Eve orbit around gilly? will ksp.exe break?

 

[Jarin]

2 hours ago, omelaw said:

 

make a damper planet at a planet's desired orbit and make a real planet orbit around damper planet at near zero (like, 10^-4m) range and inclination of whatever we want?

I'm sure KSP will hate it.. what happens if we makes Eve orbit around gilly? will ksp.exe break?

 

That unfortunately doesn't fix the fact that all bodies in the system have to have their poles in parallel. You could probably do some interesting and weird stuff with a setup like that, but inclinations are still fixed.

[pincushionman]

19 hours ago, Red Iron Crown said:

Too simple, not too complex. The coordinate systems for all the frames of reference assume North is always the same, and all the math built upon the coordinate systems (which is a *lot*) assumes it, too. It would be a monumental task to refactor the code at this point.

 

Wait wait. I don't know anything much about the code, but is the problem that "all the transformations reference the same axis (and it would be a PITA to find them all and change them to reference an arbitrary cord)", or "in all the transformations, the transformation to cord 0 is implicit in the math?" Because one of those problems is way more approachable than the other. 

After all, we already jump around between coirdinate systems, what with SOI changes and the whole shifting-origin behavior.

[Red Iron Crown]

People far smarter than me have been trying to solve this problem, some of them with access to the source code of KSP. It is not a trivial fix, it is not even a difficult fix, it's a nearly-rewrite-the-game type of fix.

[omelaw]

1 minute ago, Red Iron Crown said:

People far smarter than me have been trying to solve this problem, some of them with access to the source code of KSP. It is not a trivial fix, it is not even a difficult fix, it's a nearly-rewrite-the-game type of fix.

Like 1.1?

[Red Iron Crown]

4 minutes ago, omelaw said:

Like 1.1?

Worse, and with way less return on investment.

[Dman979]

4 minutes ago, Red Iron Crown said:

Worse, and with way less return on investment.

Not sure what you mean there, RIC. It would get Regex to stop complaining about it.

[MaxL_1023]

A change like this would be almost as significant as switching to numerical N-body simulation, if not more so. Implementing this would be worthy of a new game release - a true sequel. I would expect to see it eventually, as KSP seems to be selling enough to justify a sequal or at least a bunch of copycats. 

Axial tilt would also make the game quite incredibly annoying for newer players, with every interplanetary ejection orbit putting you onto a different solar inclination and also messing up gravity assists and all transfer burns. Mechjeb's porkchop plot could probably handle it, but it would turn into a near-necessity for interplanetary travel.