Advanced Question Rotating a Docking port

[clickypens]

I'm making a space station (who isn't nowadays?) and I want to have a Nebulus to put my truss system on. The problem is that when I dock Nebulus to any module, the truss attachment point is rotated 90º.

My question is how can I rotate a docking port 90º along it's Z axis?

 

[Andy44]

Look in your config or ini file for your space station. There should be a line for docking ports. Looks like this:

BEGIN_DOCKLIST
0 0 7.15 0 0 1 0 1 0

The first three numbers are the position of the docking port from the vessel mesh's center. The next three tell you which direction the port faces.

The final three numbers tell you which way the port is rotated about the docking axis. The port in the example is located at

x:0, y:0, and z:7.15 meters from mesh center.

The dock points in the +Z direction (0, 0, 1), and it's oriented so that "up" as you look at it is in the +Y direction (0, 1, 0).

Those last three numbers are what I think you are worried about. Always make sure the direction and orientation coordinates are a unit one in length.

Hope that helps.

---------- Post added at 12:43 AM ---------- Previous post was at 12:37 AM ----------

BTW, all this stuff is in the Orbiter docs, which are a more accurate source than I am.

 

[clickypens]

Sorry about not looking. I didn't really think about it. But thanks a ton.

---------- Post added at 09:54 AM ---------- Previous post was at 08:34 AM ----------

I've tried messing with those values and always get really weird results. I think it would be easier to post a picture.

This is what I've got. The Nebulus module (the second one from the left) has a thing on "top" to put a truss system. My problem is that the "top" is on the side.

Here is the docking part of the config file.

; === Docking ports ===
BEGIN_DOCKLIST
-0.05 0 5.4  0 0 1   0 -1 0
-0.05 0 -5.4  0 0 -1   0 -1 0
2.25 0 -1.62  1 0 0  0 0 -1
END_DOCKLIST

I've tried changing those very last digits for the first two docking ports, but to no avail. Everytime I do, the module comes out very distorted.

 

[martins]

I've tried changing those very last digits for the first two docking ports, but to no avail. Everytime I do, the module comes out very distorted.

The values can't be changed arbitrarily. If you get distorted results, then in all probability you used invalid parameters.

The conditions for the direction vector D (the second triplet of values) and the alignment vector R (the last triplet of values) are

• both must be normalised to 1 (as Andy mentioned): |D|=1, |R|=1
• they must be orthogonal, i.e. inner product zero: <D,R>=0

For example if your direction vector is (1,0,0), then you could parameterise the alignment vector with a single rotation angle a, for example

R = (0, cos(a), sin(a))

By changing a, you can rotate the longitudinal alignment of docked vessels.

 

[clickypens]

Awesome! Thank you so much Martin. I always thought that the numbers were (xyz xyz xyz). I now understand how to rearrange docking ports. Thanks a ton!