Fixed issue in SkeletonIK leading to some root bones being twisted incorrectly

[TwistedTwigleg]

Should close #48078 and close #47803 - at least I think it should.

I still have the issue where in Godot 4.0 I am unable to see meshes, but the bone gizmo seems to no longer be twisted. I tested the minimum replication projects in both of the linked issues, as well as some other projects, and the gizmos seem to be in the correct rotation.

The issue seems to be two fold: the first problem was that I was incorrectly making both of the Vector3s I was using for directions absolute, making it where bones with -Z as the forward vector would be incorrectly parsed as +Z as the forward direction. The other issue was that LookAt was using a up direction of +Y, so for bones with a forward bone direction on the Z axis, up is now +X.

That said, this needs testing to make sure the visuals are correct! It could be the rotation is off by an increment of 90 degrees, in which case I would be unable to see it in the bone gizmo. Help testing this PR to make sure it actually fixes the issues linked would be greatly appreciated!

[akien-mga]

I made builds of the PR for Windows and Linux, cherry-picked on the 3.x branch (3.4-beta, but should still be nearly identical to 3.3-stable):

• https://downloads.tuxfamily.org/godotengine/testing/Godot_v3.4-beta-pr48166_win64.exe.zip
• https://downloads.tuxfamily.org/godotengine/testing/Godot_v3.4-beta-pr48166_x11.64.zip

CC @macryc @yaelatletl @Naurk @wojtekpil Please confirm that it fixes your issue(s).

[TwistedTwigleg]

Awesome, thanks @akien-mga!

[macryc]

Cool! I'll check this afternoon and report. Thanks.

[Naurk]

@akien-mga Unfortunately this don't fix the twisted root bone for me. You can check it yourself: https://github.com/Naurk/TP-Minimal-Controller

Anyway thank you for your work.

[macryc]

I made builds of the PR for Windows and Linux, cherry-picked on the 3.x branch (3.4-beta, but should still be nearly identical to 3.3-stable):

• https://downloads.tuxfamily.org/godotengine/testing/Godot_v3.4-beta-pr48166_win64.exe.zip
• https://downloads.tuxfamily.org/godotengine/testing/Godot_v3.4-beta-pr48166_x11.64.zip

CC @macryc @yaelatletl @Naurk @wojtekpil Please confirm that it fixes your issue(s).

No, it didn't fix the issue I'm afraid. Is it possible that the code didn't get pulled into this build? Just thinking - if something got changed we'd see a different behavior but the issue looks exactly like it does in 3.3 stable.

[wojtekpil]

I made builds of the PR for Windows and Linux, cherry-picked on the 3.x branch (3.4-beta, but should still be nearly identical to 3.3-stable):

• https://downloads.tuxfamily.org/godotengine/testing/Godot_v3.4-beta-pr48166_win64.exe.zip
• https://downloads.tuxfamily.org/godotengine/testing/Godot_v3.4-beta-pr48166_x11.64.zip

CC @macryc @yaelatletl @Naurk @wojtekpil Please confirm that it fixes your issue(s).

Unfortunately, also in my case the error has not been fixed.

[akien-mga]

Is it possible that the code didn't bet pulled into this version? Just thinking - if something got changed we'd see a different behavior but the issue looks exactly like it does in 3.3 stable.

It's possible yes as it's mostly a manual process when I do a custom build like this. But I just checked and I do have the relevant changes committed so they should be part of that build normally.

I pushed the manual cherry-pick to this branch: https://github.com/akien-mga/godot/commits/3.x-pr48166
(It's the same as this PR but I had to add the up vector in the first two looking_at calls as there's no default value in 3.x.)

[TwistedTwigleg]

I just tested the Godot 3.x build linked and unfortunately it doesn't work for me either. I also just looked at the commit Akien linked and can confirm it is the same code change. It seems this PR doesn't fix it after all. This PR does fix an issue where the wrong condition is used if the bone axis is negative, so it's not totally useless, but alas it doesn't fix the bone twist issue it seems.

I'll take another swing at trying to fix it once I can. It looks like I'll need to work in the Godot 3.x branch to make the fix and then port it to master, as it seems I cannot go by the skeleton gizmo as an indicator of whether its working or not.

[TwistedTwigleg]

Took the additional changes from #48251 and put them into this PR.

[TwistedTwigleg]

The code in this PR is now a direct port of #48251 but for master instead of Godot 3.x

[akien-mga]

Thanks!