Custom Drag Cubes?

[Gryphon]

In a thread from a month ago, there was a discussion of drag cubes with some good info.

Well, 99% automatically. If your part is hollow, you will need to manually adjust its cube. That's why hollow parts have custom cubes defined in their part cfgs.

In particular, for a stackmounted hollow part, change the Y+ and Y- area values (the first numbers in the third and fourth groupings) to be the area for a non-hollow version of that part.

and

the first six triplets are X+, X-, Y+, Y-, Z+, Z- faces of the cube. The numbers are area, drag coefficient, and depth of widest point from the frontmost point at that angle. The nextr triplet is the bounds center, the final is the bounds extents.

but

Ah crap, so I do need to include them then. It's my hollow cargo bays that I'm concerned about. I'm assuming that the "A" and "B" versions are for with the doors open and closed.

Is there a way to view the calculated version so I can just tweak that to insert in the configs?

Then, I took a look at the part configs for all the Squad cargo bays and air intakes, and came up with the following:

SQUAD INTAKES AND CARGO BAYS WITH CUSTOM DRAG CUBES:

circularIntake

mk2CargoBayS

mk2CargoBayL

SQUAD INTAKES AND CARGO BAYS WITHOUT CUSTOM DRAG CUBES:

mk3CargoBayS

mk3CargoBayM

mk3CargoBayL

ServiceBay_125

ServiceBay_250

airScoop

radialEngineBody

nacelleBody

IntakeRadialLong

ramAirIntake

From that thread I quoted, and a quick perusal of the part configs, I was left with some questions that weren't answered:

What determines which parts have custom drag cubes, and which don't? Most don't. How do I determine if I need to add a custom drag cube?

Then, if I do need to create custom drag cubes:

I am updating parts for 1.0 that I didn't originally create. These include air intakes and cargo bays. What is the best way to get at the values KSP uses to automatically generate drag cubes?

Is it useful to see the KSP-generated drag cube values?

If so, is there an easy way to see the generated values?

Also, what is the first value of the custom drag cube? On the circular intake, with only one custom drag cube, it's "Default," and on the mk2cargobays, with two custom drag cubes, they are "A" and "B." What do they mean?

[NathanKell]

What determines if a part has a custom dragcube entry is "if it needs it, and someone remembers to give it one."

For example, the Mk3 cargo bays should have them, but that didn't make it in 1.0.2. One trusts it will be fixed in 1.0.3.

The "If it needs it" bit is probably more what you're asking, and that's...subjective, but there are some rules:

1. If the part is hollow like a Mkx cargo bay or decoupler, it definitely needs a custom dragcube.

2. If a part is not hollow, but "should be" -- like an intake--then it probably needs a custom cube.

Here's how you do it:

1. Make the part, export it, make the cfg (without any cube overrides)

2. Start up KSP. That will generate an entry in PartDatabase.cfg

3. Copy the entry into the part.cfg file

4. (if part is hollow): Edit the facings that are hollow based on similar facings from parts that are not hollow. I.e. for cargo bays and decouplers, copy the +Y and -Y triplets from a similar-stack-size tank. If the part is not hollow in terms of mesh, but should be (in terms of it being an intake with a flat black section that's supposed to represent a hole), you play with the drag coefficient (second number in the triplet) in the intake's incoming axis.

[Gryphon]

Excellent! that seems quite clear to me. Thanks!