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SmashBrown

Axial tilt: Is it possible?

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One thing that has struck me recently, I know KSP isn't supposed to be uber realistic. Kerbin should be spinning on a tilt if it is meant to be KSP's equivalent of earth, I don't think any of the planets do this, is there a plan for it? Or is it a problem with the unity engine. Pardon my ignorance if this is common knowledge.

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As far as I know it's not possible. I think it's due to the chosen method of planet modelling rather than Unity engine itself.

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Whether its Unity or how they model the planets, I know something doesn't support rotation around anything that isn't north/south (in a galactic sense).

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Is that so? I seem to recall one of the mods that added more planets managed axial tilt in one way or another...

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I know RSS fudges it by tilting the entire galaxy in the opposite direction so you end up with the same result, just using the Earth North/South as reference, not galactic north/south (up/down, you know what I mean, hopefully). I've never used an extra planets mod, but quick research tells me that axial tilt is hardcoded into the game as 0. Granted, that could be down to a conscious decision, or it could be a necessity. I don't think we've ever heard from the devs about this, have we?

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Hang on. I'm gonna trawl through some of the old stuff. Give me a bit.

EDIT: Here are the things I dug up:

http://forum.kerbalspaceprogram.com/threads/45519-Celestal-bodies-with-axial-tilt-obliquity

http://forum.kerbalspaceprogram.com/threads/80864-Axial-tilt-for-planets (long one; six pages, one especially good idea here)

http://forum.kerbalspaceprogram.com/threads/95489-Kerbin-axial-tilt

http://forum.kerbalspaceprogram.com/threads/70749-Axial-Tilt

http://forum.kerbalspaceprogram.com/threads/20331-A-sudden-realization-about-Kerbin

http://forum.kerbalspaceprogram.com/threads/51325-Do-the-planets-have-seasons

http://forum.kerbalspaceprogram.com/threads/51388-Things-I-Never-Knew

http://forum.kerbalspaceprogram.com/threads/61319-Give-Kerbin-Inclination-relative-to-the-Sun

http://forum.kerbalspaceprogram.com/threads/50617-Make-Kerbin-have-some-more-Earth-Like-Features

A general summary is that (1) Mu thinks it is possible, according to NathanKell, (2) it will cause an issue for newbies if Kerbin has an axial tilt, but that can be worked around by the idea in the second one on the list that I linked separately, and (3) if it can be done, only Squad could do it, and it may require a fair bit of re-coding to be accomplished.

Edited by vexx32
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I've not found any direct word from any Squad employees on the matter. :/

NathanKell apparently spoke with Mu about it, who mentioned it might have ended up in 0.24, but considering there's no axial tilt, presumably it was either forgotten or placed on the backburner.

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Maybe, if they do it, you simply don't rotate the Kerbin system and do rotate other bodies....

In unity, it would be super simple, Vector3 inclination , planet.rotation = x,y,z

All the recoding that would theoretically be needed (ideally) is change the rotation from world coordinates to local along x axis...

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Id like to see it. Not for Kerbin, I like the the way things are staged eg mun/minmus >duna >lands beyond. Maybe Dres, Eve, Val, GP2 could have tilts. Building in and timing those inclination burns would be a nice challenge and would feel super real.

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I do want to see Axial Tilt based on that idea vexx32 posted a link to, along with extra launch sites. Maybe there could be some advantage/disadvantage to using different launch sites, such as cheaper use, but you'd be off the equator and deal with that somehow. An interesting, but optional, added challenge.

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Wait.... from this thread.

http://forum.kerbalspaceprogram.com/threads/51388-Things-I-Never-Knew

Any planet on an incline plain has a reverse axial tilt...

So you could hack tilt Kerbin by just inclining everything in the kerbalverse by the reverse of the tilt you want Kerbin to have.

Sounds like a completely Kerbal way of doing it to me.

The RealSolarSystem mod did this. However, by the same token, you can only allow for the tilt of one planet. Others either have to be botched in or not at all. So, you'd not be able to have planets with differing inclinations than the ecliptic and Kerbin's. It's not really a solution to the problem, just a really fudged workaround.

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Some day I'll draw this up with diagrams but there is nothing mathematically (or I presume programmatically) in the way of the idea of enacting radial translations on anything that crosses an SOI boundary to effectively simulate planet tilt.

Imagine a 2d plane as our 3d Kerboverse, and Kerbin is tilted 10 degrees. It's actually stored in Unity as not tilted at all, but when a ship enters its SOI from outside, that ship is translated 10 degrees around the SOI circle. When it leaves again, it is re-translated back 10 degrees.

For rendering, you just* have to do it in reverse. When you are going to show the world in a SOI you're not in, just* rotate it from what it "really" is in Unity to what an axial tilt would make it look like.

*CAUTION: Non-programmer using the word "just" to describe how to program something!

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It can not be Unity's fault. I am absolutely sure that every 3D-engine can rotate things around any axis. Probably Squad have made some approximations at beginning and has not seen it enough important thing to implement after that. If they have coded reasonably it would be relatively easy task to do and I really hope that they do it now when basic stuff have done. In my opinion space flight game without axial tilts is very defective and I would do it from very start, when planets are monochromatic spheres and ships are cubes. If Squad fears that axial tilts would cause too many complaints and decrease their income, I hope that they could make it possible to mod tilts even stock planets would not use it.

If Kerbin had an axial tilt and Mun's orbit was not in equatorial plane, we could calculate solar eclipses and go to watch them on correct area. Maybe it could be a contract to make scientific measurements under solar eclipse. A degree or two between equator and Mun's plane would be enough but it would not make it any more difficult to beginners to achieve Mun. It is not easy to get inclination less than that by flying manually without any orbital information mod.

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(I hope) Nobody's saying it's Unity's fault. It's just something Squad has to focus on and code in (preferably without introducing too many new bugs), because it wasn't included in their original implementation.

I don't think it would take them that long to sort it all out, but I wouldn't put an insane amount of pressure on them for it, because as it stands nothing is really broken; the planets just don't really have any axial tilt yet. I hope they get to it soon, but they most certainly have their plate full of bugs that need fixing as well as incomplete features to finish and polish. :)

As to your suggestion, 5thHorseman, while it would work, it is more of a patchwork solution than a true resolution. That's not necessarily a bad thing, but those kinds of solutions can tend to be a little buggy, which is why I'd be hoping they do a thorough job of it when they get around to coding axial tilt. Patchwork solutions often rely on expected circumstances and actions to be taken, which can get difficult to manage, especially if you're timewarping, since you're skipping physics steps.

Sure, they could drop you out of warp before you exit an SOI, but that's already proven to be an unreliable way to handle things, as you can see by warping right through a planet using a high warp factor -- because the step is so large, the planet's surface and atmosphere is ignored entirely, even if the game ought to have stopped you in its atmosphere, or shortly before colliding with its surface. What you expect in the circumstances and what happens invariably tend to be ever so slightly different. Much better, in my opinion, to fix it thoroughly and implement it as a core game function where it doesn't need to be fudged. Avoids all the tricky bits that occur with a patchwork job. :)

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If they added it to Minmus I could actually get to the darn equatorial stations I've set up. As of yet, even a 0 degree relative inclination to Minmus on approach gives you a weird final inclination in Minmus SOI. :(

Waiting for Minmus to get to the Ascending/Descending node would work, but that takes forever.

It seems as if the devs programmed the planets to have 0 degrees of tilt in the global rotation system. If they could recode to put bodies in a local system, the problem might be solvable. Maybe in 0.92.0, as 0.91.0 is the Aero patch, or so it seems.

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but all you have to do to change rotation from global to local is change "thing.rotation" to "thing.localrotation" Litterally.

The hardest part is making sure the axis you use is actually the one you want.

I suspect its not balance or difficulty to implement, but rather something being mucked with, like aerodynamics to make it seem right....

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On 11/8/2018 at 7:14 PM, DAL59 said:

 

The Deep Space Kraken

WOULD LIKE TO KNOW YOUR LOCATION

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