docking alignment problem

[antipro]

I've realized that if the docking port isn't on the same SS core axis, there's no way to make a smooth docking between a station and a module.
Cause I have to move the station manually at first, and then the SS port doesn't follow the module port.
If I'm wrong correct me.

[HvP]

8 hours ago, antipro said:

I've realized that if the docking port isn't on the same SS core axis, there's no way to make a smooth docking between a station and a module.
Cause I have to move the station manually at first, and then the SS port doesn't follow the module port.
If I'm wrong correct me.

Correct, that looks like the only way it works right now. Control points only track targets properly when they are aligned with the root part's axis.

I tested this by placing different types of docking ports, command pods, and probe cores around a cylindrical test vehicle. If my root part was in the central stack then only the docking ports at either end of the stack held the target properly when at close approach for docking. Any docking ports or control points that were offset from the central stack or aimed radially outwards do not track properly.

HOWEVER! If you use the re-root tool to make a radially mounted docking port the root port then that docking port DOES track the target correctly. Further testing shows that when SAS is tracking a target it will align your navball to face in the direction of whichever control point you've selected BUT it will use the base of the root part of the craft to determine "center" for tracking purposes and calculates the angle from the target to the base of the root part - instead of the angle from the target to the selected control point. This means that if you are using a large ship and its root part is placed at some lateral distance from the docking port you are controlling from then the SAS will keep turning your ship to bring the base of its root part in line with the target - which causes the docking port you are trying to use to continue to point away from the targeted docking port.

@bewing I have updated the bug-tracker for this issue to include the above steps to replicate the problem. Maybe you have some thoughts on this. Again, for SAS "hold target" tracking the angle from the target docking port is being calculated to the base of the root part of the ship being controlled rather than calculating the angle to the selected control point.

Edited February 26, 2018 by HvP

[bewing]

3 hours ago, HvP said:

for SAS "hold target" tracking the angle from the target docking port is being calculated to the base of the root part of the ship being controlled rather than calculating the angle to the selected control point.

Oh! So that's what it is! I was having a hard time figuring out where the stupid angle was coming from. Thanks!

Edited February 26, 2018 by bewing

[HvP]

9 hours ago, bewing said:

Oh! So that's what it is! I was having a hard time figuring out where the stupid angle was coming from. Thanks!

Thank you @bewing for following up on this thread. It's so easy to overlook since most of us tend to dock with relatively small craft with center stack attached docking ports on the front. I'm not surprised the bug squeaked through until now.

And big thanks to @antipro for some extremely helpful demonstrations of the problem. Hopefully, it won't be too hard to address in further bug patches.

20 hours ago, antipro said:

I've realized that if the docking port isn't on the same SS core axis, there's no way to make a smooth docking between a station and a module.
Cause I have to move the station manually at first, and then the SS port doesn't follow the module port.
If I'm wrong correct me.

The best thing you can do in this situation is manually align the station's docking port with your smaller craft then just set it to SAS hold position (not target tracking). Then switch to your smaller craft and rotate it into a straight line with the station's docking port before coming in close for final docking.

[adriangm44]

How did you solve this? The same is happening to me. When I dock a docking port to a orbiting station, the ports move 45º and it shakes the entire station by the force given. Could you solve it?