Dagger

[1.5.X] Tilt'Em (Planetary axial tilt) [v1.0.0] [25 Oct 2018]

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Fantastic work.  I think I speak for a lot of us when I say I've been waiting for this for roughly forever.

 

Just tried it out, and launching into the plane of the moon definitely required a rethink.  Awesome!

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26 minutes ago, Gordon Dry said:

Dumb (??) question:

Will this "break" contracts for specific orbits?
(Considering the fact that ContractConfigurator is picky and many contracts create issues whatsoever :D )

Not dumb at all. It's a good question.

 

One more - I wonder how will Trajectories handle this.

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And another question.

The .cfg file specifies the tilt angles. What are the axes those rotations are around? I have a feeling they must be around the KSP solar prime vector, but want to be sure.

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33 minutes ago, Motokid600 said:

Great work, but I gotta ask. Why has it taken so long for something like this in KSP?

Older Unity apprently couldn't support it. I thought the new one was unable to do it, too.

This should be bought and set up as a feature of the stock game.

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@Dagger do you think it's possible to "inject" the tilt into the stock readout?

j2GwtPu.png

And btw will mods like KER, VOID, BasicOrbits or MechJeb get an API to read the value?

Edited by Gordon Dry

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I just thought about the NavBall.  How is it oriented?  Is N-S still up-down, or is it tilted to the axis?  This is really part of the same issued I talked about with the coordinate systems.

@Dagger, I love what you've done here and I believe it has great potential, but I think there are farther reaching issues that need to be addressed to really make it practical to implement.  Perhaps there are other members of the mod community, such as the KER and MechJeb devs ( @jrbudda and @sarbian ), that should get involved.  There really need to be a way for the game to recognize the tilt of the axis and have the NavBall and position/orbital element readouts displayed in a geocentric-equatorial system.  Perhaps there could be a way to toggle between the current coordinate system and one relative to the equator of the current body.

The issue about orbit contracts is also a very good point.

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2 hours ago, HebaruSan said:

Sounds good, thanks. Will the Kopernicus plugin be submitted to be part of Kopernicus itself, or will it still be a part of TiltEm? Asking because if you're going to integrate this into Kopernicus, then it might not be necessary to index it as a separate mod.

First I want to finish the kopernicus plugin, I'm thinking about doing it as another ".zip" in the release artifacts. Will se once I've finished it

1 hour ago, Gordon Dry said:

Dumb (??) question:

Will this "break" contracts for specific orbits?
(Considering the fact that ContractConfigurator is picky and many contracts create issues whatsoever :D )

I don't think they will be broken, orbits are independent of the tilt of the planet

1 hour ago, lajoswinkler said:

Not dumb at all. It's a good question.

 

One more - I wonder how will Trajectories handle this.

No idea about other mods but it shouldn't affect it

1 hour ago, Motokid600 said:

Great work, but I gotta ask. Why has it taken so long for something like this in KSP?

Everybody said that it was impossible and I never really tried it until I got a bit tired of LMP

49 minutes ago, Pand5461 said:

And another question.

The .cfg file specifies the tilt angles. What are the axes those rotations are around? I have a feeling they must be around the KSP solar prime vector, but want to be sure.

It's the angle against the "UP" universe vector (consider it against the equator of the sun plane)

22 minutes ago, Gordon Dry said:

@Dagger do you think it's possible to "inject" the tilt into the stock readout?

j2GwtPu.png

And btw will mods like KER, VOID, BasicOrbits or MechJeb get an API to read the value?

Probably yes, I will have a look at it later on ;)

21 minutes ago, OhioBob said:

I just thought about the NavBall.  How is it oriented?  Is N-S still up-down, or is it tilted to the axis?  This is really part of the same issued I talked about with the coordinate systems.

@Dagger, I love what you've done here and I believe it has great potential, but I think there are farther reaching issues that need to be addressed to really make it practical to implement.  Perhaps there are other members of the mod community, such as the KER and MechJeb devs ( @jrbudda and @sarbian ), that should get involved.  There really need to be a way for the game to recognize the tilt of the axis and have the NavBall and position/orbital element readouts displayed in a geocentric-equatorial system.  Perhaps there could be a way to toggle between the current coordinate system and one relative to the equator of the current body.

The issue about orbit contracts is also a very good point.

To be honest I dind't fully tested it as I'm not so good at playing KSP. Anyway if you find a bug feel free to open a github issue and I'll solve it :P

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Great idea, great mod.

I'm with OhioBob, this has a lot of potential. Many people will find this interesting. Lets see where it goes.

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2 hours ago, Dagger said:

Example: This is how a 90º orbit looks like when Kerbin is tilted:

4HgGNyr.png

What a cool mod, and I'm thrilled to see this appear! :D

The above does puzzle me a little, though. Maybe I have some un-learning  to do, but wouldn't a "90 degree" orbit still be considered around the planet's axis of rotation? (Or would a 90 degree orbit of Uranus be a polar orbit? :D )

If this is an issue to work through, maybe padding the orbit's reported value to properly reflect what's happening in-game?

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5 minutes ago, Beetlecat said:

What a cool mod, and I'm thrilled to see this appear! :D

The above does puzzle me a little, though. Maybe I have some un-learning  to do, but wouldn't a "90 degree" orbit still be considered around the planet's axis of rotation? (Or would a 90 degree orbit of Uranus be a polar orbit? :D )

If this is an issue to work through, maybe padding the orbit's reported value to properly reflect what's happening in-game?

Yeah I think I must apply rotation to the navball too... Will have a look at it

Edited by Dagger

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unknown.png

Works with custom planets, but better to wait for Kopernicus plugin state

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I've been doing some experimenting and what I'm seeing is a combination of good news and bad news.  First, the good news.  I think the NavBall and KER's surface latitude/longitude readout are correct.  Both appear to be recognizing the tilt and are accommodating for it.  The bad news is that KER is providing orbital elements relative to the ecliptic.  That is, when I put a vessel in an equatorial orbit around Kerbin, KER says my orbital inclination is 23.4 degrees.  If there were some sort of a toggle in KER to switch to a geocentric-equatorial readout, I think everything would work great.  I didn't test MechJeb because I don't use it and I'm not familiar with it.

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First of all, amazing work! I'm super hyped to see someone finally add this long-needed feature to KSP. I look forward to the ongoing development of this mod!

I am having one problem though. Every time I edit the .cfg file, all planets revert to 0 degrees of tilt, except for Kerbin which maintains the default 23.4 degrees. If i drop your supplied and un-modified .cfg back into the install, all planets regain your modifications. 

Are there any limitations to what values can be input? Number of digits after the decimal point, for example? Or is the file in a structure that notepad / wordpad cannot edit safely?

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4 minutes ago, OhioBob said:

I've been doing some experimenting and what I'm seeing is a combination of good news and bad news.  First, the good news.  I think the NavBall and KER's surface latitude/longitude readout are correct.  Both appear to be recognizing the tilt and are accommodating for it.  The bad news is that KER is providing orbital elements relative to the ecliptic.  That is, when I put a vessel in an equatorial orbit around Kerbin, KER says my orbital inclination is 23.4 degrees.  If there were some sort of a toggle in KER to switch to a geocentric-equatorial readout, I think everything would work great.  I didn't test MechJeb because I don't use it and I'm not familiar with it.

Ideally we could also change the tilt angle in the map view as well.

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@Dagger, I've found a problem.  The line of nodes of the equator randomly changes from one game launch to the next.  For instance, put a satellite in an equatorial orbit (you'll have to figure out the LAN by trial and error).  Shut the game down and restart.  The planet's axis will now be pointed in a different direction and the satellite will no longer be orbiting around the equator.  I did it three times.  First time the LAN was 84.54 degrees, second time it was 198.33, and the third time it was 266.13.

It looks just like a problem we use to have with planetary rings.  Any time we tried to incline rings, the LAN kept randomly changing.  Kopernicus eventually added a longitudeOfAscendingNode parameter for rings that locked down their orientation.  It looks like you may have to do something similar with axial tilt.

 

Edited by OhioBob

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3 hours ago, Beetlecat said:

What a cool mod, and I'm thrilled to see this appear! :D

The above does puzzle me a little, though. Maybe I have some un-learning  to do, but wouldn't a "90 degree" orbit still be considered around the planet's axis of rotation? (Or would a 90 degree orbit of Uranus be a polar orbit? :D )

If this is an issue to work through, maybe padding the orbit's reported value to properly reflect what's happening in-game?

That's the Navball issue alluded to upthread. The 90 degrees is relative to solar north, not Kerbin rotational "north".

For those asking why this hasn't been done before, it has - in 1.0.5:

This mod avoids several of the issues that Harder Stock System has.

BTW, well done @Dagger I am really looking forward to trying this out!

Edited by panarchist

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18 minutes ago, OhioBob said:

@Dagger, I've found a problem.  The line of nodes of the equator randomly changes from one game launch to the next.  For instance, put a satellite in an equatorial orbit (you'll have to figure out the LAN by trial and error).  Shut the game down and restart.  The planet's axis will now be pointed in a different direction and the satellite will no longer be orbiting around the equator.  I did it three times.  First time the LAN was 84.54 degrees, second time it was 198.33, and the third time it was 266.13.

It looks just like a problem we use to have with planetary rings.  Any time we tried to incline rings, the LAN kept randomly changing.  Kopernicus eventually added a longitudeOfAscendingNode parameter for rings that locked down their orientation.  It looks like you may have to do something similar with axial tilt.

 

I was about to mention this same issue as well. 

A LAN parameter similar to the orbital LAN values really is required in order to 'lock' the tilt to a certain direction. This will also allow for the easy matching of a planet/moon's axial tilt to its orbital tilt, something that many real life moons tend to have.

On a related note, perhaps the tilt Vale of '0' can be modified to be relative to the objects orbital plane instead of relative to the main solar system's coordinate system? From what I can tell in real life examples, this is the more common baseline.

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12 minutes ago, panarchist said:

That's the Navball issue alluded to upthread. The 90 degrees is relative to solar north, not Kerbin rotational "north".

It makes total sense as to why it's appearing that way--but would it make a logical, navigational sense to orient to solar north? It just seems a strange artifact of this cool new effect for the time being.

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35 minutes ago, OhioBob said:

It looks just like a problem we use to have with planetary rings.  Any time we tried to incline rings, the LAN kept randomly changing.

Indeed, I think it's essentially the same issue. It had been a while, but luckily I left a comment that:

Quote

"World" coordinates seem to be set differently each time the game is loaded.

... which would cause exactly what you describe. The same solution/workaround may need to be applied (deriving a truly absolute reference direction by subtracting off the body's total rotation since UT=0).

Can I suggest that folks posting problems here report them on the mod's GitHub? Very active threads like this are a living heck for issue tracking:

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22 minutes ago, VonFrank said:

From what I can tell in real life examples, this is the more common baseline.

Depends on the application. Here, setting up the orbital inclination and axial tilt is easier if you set the ecliptic as the reference point.

On the point of the "LAN locking": yes, it should be available since axial tilt is actually defined by both the Right Ascension and Declination angles of the body's north pole.

Edited by Phineas Freak

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22 minutes ago, Beetlecat said:

It makes total sense as to why it's appearing that way--but would it make a logical, navigational sense to orient to solar north? It just seems a strange artifact of this cool new effect for the time being.

No, it wouldn't. I wasn't advocating for it, just saying that's why it's happening. I don't know what would need to be changed on the Navball end to have it display "correctly" in this case.

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32 minutes ago, VonFrank said:

On a related note, perhaps the tilt Vale of '0' can be modified to be relative to the objects orbital plane instead of relative to the main solar system's coordinate system? From what I can tell in real life examples, this is the more common baseline.

12 minutes ago, Phineas Freak said:

Depends on the application. Here, setting up the orbital inclination and axial tilt is easier if you set the ecliptic as the reference point.

@VonFrank, yes, the axial tilt of a planet is usually expressed relative to the plane of the orbit.  But I agree with @Phineas Freak that it's probably easier to use the ecliptic as the reference point.  If it's really so important that tilt relative to the orbit must be known, the developer may just have to mathematically convert from one reference plane to the other.  If it becomes necessary, I can probably figure out the conversion.

 

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Congratulations, you probably just gave me a ton more work to revamp KSP Trajectory Optimization Tool to support this lol. :sticktongue:

So alright, question: are orbits around local bodies, like Kerbin, computed w.r.t. the body's new rotation axis and equatorial plane?  For example, if I tilt Kerbin and then launch due east from the equator, I will be in an equatorial orbit.  Is the inclination of that orbit with your mod 0 degrees (because it's measured against Kerbin's new equator) or something else (because it's measured against the universal coordinate system)?

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