ZDoom

That helps clearing things up and continueing work. But this means also that MaxED should take care of that concerning GZDoomBuilder :)

In that case: change the mod. Despite my best efforts I haven't found anything that depends on this inconsistency.

In normal circumstances, -pitch = aiming up. I.e. A_SetPitch(pitch-5) will kick the aim of a player upwards.

I need some feedback. How is pitch handled elsewhere? Is positive pitch upward or negative?

The question generally is now, if we as modders need to change the mods or if GZDoom's code will be changed instead?

Is this the sort of thing you could preemptively add an internal compat flag for, then fix anyway?

The problem is solely the 'pitch' property in UDMF. Due to the incorrect internal model rotation they are all positive when they really should be negative in the attached test map. Neither GeneTech nor Paranoid use UDMF so neither mod is affected.
In ZDoom, a negative pitch points upwards and a positive pitch points downwards and this has to be respected, otherwise all sorts of errors will come up.

Enjay used a ton of models in his GeneTech mod, and also Rex's Paranoia mod. Perhaps those projects would have a lot of test material to check with?

I hope you'll get necessary info to fix this...
I really don't want to rotate hundred of models here and there and see them misplaced while building a map...
I wrongly think that this consideration of mine was enough for you to "fix" the issue, but I am not a developer and I could only imagine things this way then.
Hopefully something will happen. Thanks in advance anyway, GZDoom rocks in any case and this will never change eheh :cool:

I still need to decide whether to flip the pitch in UDMF or not. Right now I have insufficient information.

So THIS was what broke my pitched model stuff, LOL!

Eh, no biggie, I guess I can just flip the signs mod-side; it's just a matter of me being nervous now because I just can't stop thinking of how many things I need to fix and the possibility of me missing something...

The problem is, the pitch calculations for 'inheritactorpitch' had been wrong forever and treated positive pitch as 'upward' whereas internally it is 'downward'. That essentially meant that anything using actual pitch pointed in the wrong direction.
I could change the UDMF property to change its sign, too, but I have no idea what new problems THAT might introduce. With people refusing to upload their mods to /idgames and instead opting to host them elsewhere it has become impossible to get a comprehensive list of mods to check. It was easier when this kind of private hosting was less commonplace.

Ironically the actor pitch and the pitch of projectiles spawned from that actor both align (properly?) now.

You can see this in my [url=http://afadoomer.com/files/SpotlightTest.pk7]Spotlight Test[/url] .pk7 file ('summon spotlight 0' and kill any monsters, because autoaim). This is basically an actor set up to mirror the player's pitch. In older builds, the actor's model pitch correctly follows the player pitch, but projectiles (<!> sprites and the spotlight glow) are mirrored across the horizontal axis.

I'd love for this to be normal behavior for projectile pitch calculations, but I think there would need to be a flag to keep the old behavior...

While this is strange that nobody here told you this before, I see that the pitch doesn't work correctly since g2.2pre-1504-g47064e2 of GZDoom.
It works as intended with pre-builds since r1471.

[url=http://imgur.com/a/SBBbv]Some screenies to show you what's going on[/url]

[attachment=0]PITCHY.zip[/attachment]