In-flight gimbaling does not work for SRBs in latest release

[MikeOnTea]

Worked fine before, now does not work for either lower or upper stage SRBs.

[blowfishpro]

I saw gimbal working for the upper stage SRBs (at least for those nozzles that gimbal). I saw gimbal not working for the new 4 nozzle lower stage one, but I didn't check the rest

[MikeOnTea]

The new 4 nozzle lower stage has set the gimbal limit to 0 explicitly. Weird that it works for you, maybe i should try a completely new vessel... Thanks for commenting.

Edit: Doesn't work with a completely new rocket, either.

[taterkerman]

I'll test this later tonight and see if I can replicate it.

[shadowmage45]

Several of the nozzles have gimballing explicitly disabled; the 4-nozzle lower stage, and the two upper-stage nozzles that have no gimbal actuators are all fixed, and should have no gimbal control in flight.

The rest though, should certainly have gimbal; you should even be able to see the nozzles move, and the actuators do their thing. If this is not working, please confirm, and I will investigate this evening/later this week.

[MikeOnTea]

I have tested several lower stage nozzles other than the 4-nozzle and they don't gimbal for me, not visually and not functionally. Works perfectly with the old sstu version.

[blowfishpro]

@shadowmage45 how come you disabled gimbal on the 4 nozzle lower stage? I think I set up the model so that it could gimbal.

[shadowmage45]

@blowfishpro The lower-stage 4-nozzle looked 'fixed' to me (no visible actuators/etc). Would be easy enough to adjust the config to allow some minor (1-2') gimballing -- it is setup to use the thrust transform as gimbal, so would actuate the thrust transform directly (no visible nozzle gimballing).

Would require re-rigging and re-export of the model to enable moving nozzles. As I need to re-export the model anyway to fix some tangent consistency issues that are causing visible seams (mirror modifier = bad for Unity auto-calc'd tangents), I could add in explicit gimbal transforms if desired.

[blowfishpro]

I mostly didn't include the actuators because I figured that no one would ever see them.

[shadowmage45]

@MikeOnTea Can confirm this issue in testing on the release version. Not sure what/where things went wrong, gimbals were certainly working last I tested them in flight (which was as/after I got the RCS stuff working).

Will step backwards through the commits to find the last working version, run a diff, and find out what all code/config changes were done that could have caused problems.

@blowfishpro I'll add in some gimbal transforms to that model when I re-export it next; already need to do so in order to capture some minor UV changes and fix the tangent seams. Won't hurt to have the transforms there and in place, even if not used (though I'll likely add a few degrees of gimbal range to the configs).

[shadowmage45]

Okay, so after some investigation I have found out what is going on.

• Any nozzle that uses distinct transforms for gimbal and thrust transform works properly (e.g. the gimbal-actuator-equipped upper-stage nozzles all work).
  • SRB-UB, UC, UD nozzles all work fine.
• Any nozzle that uses the same transform for both thrust transform and gimbal transform fail. As the code tries to rename the same transform twice (one transform used for both thrust and gimbal), with only the first rename action working (which is to rename the existing thrust transform to the name specified in the config).

As such, in order to fix the problem properly, I will need to re-export all SRB nozzles to include distinct, separate, and unique thrust and gimbal transforms in the proper hierarchy (including the older legacy / lower-stage nozzles that lacked distinct gimbals).

This also would explain why it didn't show up in pre-release testing -- I was concentrating on testing the nozzles that had visible gimbal actuators and/or RCS; which all work properly.

Edit: Hmm... this is making less sense, as the existing models/nozzles do have different transforms for both gimbal and thrust (usually the gimbal is the nozzle mesh). Looking further now, but I have an idea (part config error).

[shadowmage45]

Indeed, this particular problem is a config-level error that can easily be corrected.

The following patch file will temporarily fix the problem:

@PART[SSTU-SC-ENG-SRB-A]
{
    @MODULE[SSTUModularBooster]
    {
        %gimbalTransformName = SSTU-MSRM-GimbalTransform
    }
}

However the issue regarding engines using the same transform for both thrust and gimbal still exists, and I will need to adjust at least a couple of the new upper-stage nozzles (the older lower-stage nozzles all use different transforms for gimbal/thrust).

[MikeOnTea]

Thanks, that indeed fixes it. While looking at the upper stage SRBs, i noticed another problem with the fire/exhaust animation though, opened issue #569.