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Centre of Mass and “Control from Here


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Okay guys I play the KSP “Enhanced” edition on PS4 and I’m familiar with the age old bug of the control from here function not working correctly when the desired control point does not fall along the centre of mass. The only threads I could find on the issue were about 3 years old at best.
 

KSP has had plenty of updates since then yet I am having the same problem with the game today. My question is has this bug got a workaround yet?? 

Any help on this would be greatly appreciated!!

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3 hours ago, AHHans said:

Hi @ReigningArrow, welcome to the Forums.

I play on PC, so it might be different there, but I'm not aware of an actual bug concerning the control point not being in line with the CoM. Can you explain that a bit?

It used to be that if you tried to "control from here" on a surface attached docking port. rather than aligning the control axes to those of the port, the game would draw a line from the COM of the root part to the port and align the axes to that instead.

Over time updates to how the game handles roots, parents and control points have mitigated the bug, So i have not been able to replicate it on PC current version, but i recall it still being an issue for edge cases back in 2018. 

not sure how far behind the console ports are.

Some Screenshots would help.

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28 minutes ago, Rhomphaia said:

It used to be that if you tried to "control from here" on a surface attached docking port. rather than aligning the control axes to those of the port, the game would draw a line from the COM of the root part to the port and align the axes to that instead.

Ah, O.K. On PC (well, on Linux, but I don't expect the other versions to be different) this seems to be fixed: I didn't even knew this issue existed, and many of my craft have docking ports that are not in line with the CoM. (In other words: I'm sure  that I would have noticed that if it still were an issue.)

The one thing I did notice during docking is that the prograde / retrograde marker on the navball is not from the control-point docking port to the target docking port - as the target direction marker is - but from the local CoM to the target.

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27 minutes ago, AHHans said:

The one thing I did notice during docking is that the prograde / retrograde marker on the navball is not from the control-point docking port to the target docking port - as the target direction marker is - but from the local CoM to the target.

Yeah, I've noticed that too, seems like this could be the culprit for the OPs case, the bug I mentioned was pretty old and mostly fixed by 1.4 and the enhanced edition is more recent than that.

Funny thing is I don't remember the prograde/retrograde markers being an issue in older versions. one bug squashed, another one rears it's ugly head.

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6 hours ago, AHHans said:

Hi @ReigningArrow, welcome to the Forums.

I play on PC, so it might be different there, but I'm not aware of an actual bug concerning the control point not being in line with the CoM. Can you explain that a bit?

 

2 hours ago, Rhomphaia said:

It used to be that if you tried to "control from here" on a surface attached docking port. rather than aligning the control axes to those of the port, the game would draw a line from the COM of the root part to the port and align the axes to that instead.

Over time updates to how the game handles roots, parents and control points have mitigated the bug, So i have not been able to replicate it on PC current version, but i recall it still being an issue for edge cases back in 2018. 

not sure how far behind the console ports are.

Some Screenshots would help.

Thank you for your replies @AHHans and @Rhomphaia I’ve attached a screenshot that should illustrate my issue hereak0Sc2i.jpg

the way my spacecraft is set up is that it consists of a main craft consisting of 2.5m parts at the core and has a pair of Mk2 sized “booms” either side of it at the stern of those booms there are shielded ports which I put in to dock with however my issue is since these ports  are not along the centre of mass they won’t line up when I use the docking port as a control point and target the destination port with SAS

Ak5pyw8.jpg

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1 hour ago, ReigningArrow said:

however my issue is since these ports  are not along the centre of mass they won’t line up when I use the docking port as a control point and target the destination port with SAS

Ah! Yes, that is indeed still/also an issue in the PC version: when selecting SAS "point to target" then it will indeed not point in the right direction if the control point is not in line with the CoM. That hasn't been a big issue for me, because as far as I can tell it only affects the direction that SAS points toward and only when using "point to target" ("point to prograde / retrograde" is correct / as I expect it to be). The actual control of the craft - e.g. in which direction the craft moves when I use RCS translate or in which direction it rotates when I rotate it - is also correct, as are the displays on the navball. So what I do is to manually keep the craft oriented the right way. It is somewhat more complicated but I consider it "good training". But I don't know of a workaround or fix that will automatically point in the right direction in this case.

P.S. The craft where I have this issue the most is with my shuttle spaceplanes, like the one I used for the K-Prize challenge. (In there I also commented about that in the "hidden" section about docking to the Gateway Station.)

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The player who entered the bug report figured out it depended which part was 'root' in the craft under SAS control.  The navball is correct but for some reason SAS holds orientation not so that the docking port points to the target, as you would expect, but so that a line from the root part to the target is parallel to the docking-port axis.

So in some cases you might work around the bug in the VAB, by choosing the root part to be along the axis of the docking port.

Or, try the other approach to docking: Orient the ship so the docking port is parallel to the target port, ask SAS to hold orientation, and translate to dock.

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So it is something like the old bug still? but now only affects SAS.:/

Generally hold target is my least used SAS mode.My preferred dockin method is to ensure targets docking ports are aligned Normal or AntiNormal to orbit, then when I approach I set SAS to hold the opposite, and translate into position.

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40 minutes ago, Rhomphaia said:

So it is something like the old bug still? but now only affects SAS.

Yes, but: I just gave it a test run and a) a few week of Rimworld - Royalty and my piloting skills are shot to hell, and b) is that fixed?!?

My spaceplane doesn't seem to behave in 1.9.1 like I remember it doing... But a real investigation of this will have to wait till tomorrow!

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3 hours ago, AHHans said:

Ah! Yes, that is indeed still/also an issue in the PC version: when selecting SAS "point to target" then it will indeed not point in the right direction if the control point is not in line with the CoM. That hasn't been a big issue for me, because as far as I can tell it only affects the direction that SAS points toward and only when using "point to target" ("point to prograde / retrograde" is correct / as I expect it to be). The actual control of the craft - e.g. in which direction the craft moves when I use RCS translate or in which direction it rotates when I rotate it - is also correct, as are the displays on the navball. So what I do is to manually keep the craft oriented the right way. It is somewhat more complicated but I consider it "good training". But I don't know of a workaround or fix that will automatically point in the right direction in this case.

P.S. The craft where I have this issue the most is with my shuttle spaceplanes, like the one I used for the K-Prize challenge. (In there I also commented about that in the "hidden" section about docking to the Gateway Station.)

 

2 hours ago, Rhomphaia said:

So it is something like the old bug still? but now only affects SAS.:/

Generally hold target is my least used SAS mode.My preferred dockin method is to ensure targets docking ports are aligned Normal or AntiNormal to orbit, then when I approach I set SAS to hold the opposite, and translate into position.

 

2 hours ago, OHara said:

The player who entered the bug report figured out it depended which part was 'root' in the craft under SAS control.  The navball is correct but for some reason SAS holds orientation not so that the docking port points to the target, as you would expect, but so that a line from the root part to the target is parallel to the docking-port axis.

So in some cases you might work around the bug in the VAB, by choosing the root part to be along the axis of the docking port.

Or, try the other approach to docking: Orient the ship so the docking port is parallel to the target port, ask SAS to hold orientation, and translate to dock.

Thank you all at least now I know this is an issue I’ll just have to pilot my way around and hope squad and the company that ports KSP onto console patch up soon. God this game is good but desperately needs bug fixes. 

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O.K. I looked into it again, and indeed in 1.8.1 doing SAS point to target with the off-axis docking port leads to the "expected" misalignment.

But doing the same in 1.9.1 just led to a successful docking. :D The docking port kept pointing straight at the target.

So I checked the 1.9.0 changelog and indeed I found the following line:

* Fix SAS target mode misalignment when control point is not the vessel root

So, yes, that seems to be fixed. And if I see it correctly they also fixed the misalignment of the prograde marker on the navball that I mentioned. (But I haven't tested that extensively.)

12 hours ago, ReigningArrow said:

Thank you all at least now I know this is an issue I’ll just have to pilot my way around and hope squad and the company that ports KSP onto console patch up soon. God this game is good but desperately needs bug fixes. 

You're welcome, so do I, and indeed.;)
AKA: I'm happy to have been of help. I also hope that the recent bugfixes make it to the console version soon (but I'm not willing to hold my breath until then). And I totally agree that there are many more - and IMHO more annoying - bugs to be fixed.

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1 hour ago, AHHans said:

And if I see it correctly they also fixed the misalignment of the prograde marker on the navball that I mentioned. (But I haven't tested that extensively.)

Well, that was apparently fixed sometime between 1.7.3 and 1.8.1.

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