Animating models without animations through bone overrides only doesn't work in 5.15.x

[SeqSEE]

Luanti version

Luanti 5.15.1 (from Flatpak)

Operating system and version

Kubuntu 24.04.4

CPU model

AMD Ryzen Threadripper 3960X

GPU model

NVIDIA GeForce RTX 3060

Active renderer

4.6.0 / opengl3 / SDL 2.32.62 (COMPAT)

Summary

set_bone_override no longer works in 5.15.1. The same bit of code works in 5.14.0.

Example code:
https://github.com/CryptechTest/voxel_annihilation/blob/main/mods/va_structures/structures/t1/economy/vox_wind_turbine.lua#L67-L80

2026-02-28.08-36-05.mp4

Steps to reproduce

Use set_bone_override to set the rotation of a bone of glTF model. Logging the override shows that it changes, but has no visual effect.

[SmallJoker]

#16609 was one of the changes that happened in the meantime. Question is whether that's the cause. Needs bisecting.

@appgurueu Might you have a few ideas (when you've got some capacity) ?

[appgurueu]

Nothing off the top of my head I'm afraid. What makes this confusing is that it applies specifically to glTF among a bunch of model formats that end up as SkinnedMeshes. A bisect would be very helpful. It might take a while before I have the time for a longer debugging session.

[SeqSEE]

Nothing off the top of my head I'm afraid. What makes this confusing is that it applies specifically to glTF among a bunch of model formats that end up as SkinnedMeshes. A bisect would be very helpful. It might take a while before I have the time for a longer debugging session.

I actually don't know if it is just glTF, but that's what we are using for our models in our game. If there's anything else I can do to test further or to provide more info feel free to let me know.

[appgurueu]

Well, character anim still works in 5.16.0-dev-4f12cc04f with character.b3d, so bone override rotations don't seem to be broken in general.

[Merrokitsune]

When the game got updated to 5.15.0, my character model (which is in gltf) got stiff, and the entity (that is supposed to display the item the player is holding) attached to the model's right arm began to move wildly, as the bone overrides somehow got transferred to said entity.
This is a screenshot of a test game in 5.15.1. The black pixel around the player model is the entity.

In this screenshot, the player is holding a grass block.

[appgurueu]

Thanks for the report. If I try to make a minimal reproducer out of the devtest spider:

diff --git a/games/devtest/mods/gltf/init.lua b/games/devtest/mods/gltf/init.lua
index 2f70e8b39..9941b9d5b 100644
--- a/games/devtest/mods/gltf/init.lua
+++ b/games/devtest/mods/gltf/init.lua
@@ -39,6 +39,18 @@ core.register_entity("gltf:spider_animated", {
        },
        on_activate = function(self)
                self.object:set_animation({x = 0, y = 140}, 1)
+               local x = 1
+               local function rotate_head()
+                       if not self.object:is_valid() then
+                               return
+                       end
+                       x = 1 - x
+                       self.object:set_bone_override("Head", {
+                               rotation = {vec = vector.new(math.pi * x, 0, 0), absolute = true, interpolation = 1.0},
+                       })
+                       core.after(1, rotate_head)
+               end
+               rotate_head()
        end
 })

the rotation override works as expected (tested on 5.16-dev, 5.15.0, 5.15.1):

Screencast.From.2026-03-08.11-33-17.mp4

There seems to be a factor beyond "set rotation override on bone of glTF model" at play here.

If either of you could isolate a failing case to a "minimal reproducer" mod, I would greatly appreciate that.

---

Edit: Had a hunch this might be related to rigid animation (Blockbench exports), tried it with the glTF frog, still no dice (working as expected with leftleg).

---

One theory: The commit SmallJoker linked does change the behavior of getting bone overrides slightly, which is what e.g. the linked "voxel annihilation" code might be affected by. Though I'm not sure how that would affect the player model.

[Merrokitsune]

One theory: The commit SmallJoker linked does change the behavior of getting bone overrides slightly, which is what e.g. the linked "voxel annihilation" code might be affected by. Though I'm not sure how that would affect the player model.

It might have to do with the "set_attach". I think this screenshot of a snippet might be helpful, right?

I am, however, still baffled, because despite me preventing this code (or the entity from being spawned) from being run by commenting, the playermodel remains stiff.

[SmallJoker]

set_bone_override no longer works in 5.15.1. The same bit of code works in 5.14.0.

Example code:
https://github.com/CryptechTest/voxel_annihilation/blob/main/mods/va_structures/structures/t1/economy/vox_wind_turbine.lua#L67-L80

@SeqSEE Cannot reproduce. The node va_structures:vox_wind_turbine and enttiy va_structures:vox_wind_turbine_entity are removed immediately. Please provide concise instructions or - preferably - a mod that is reduced to the minimum as requested by @appgurueu above.

[SeqSEE]

Here's minimal example mod that uses the step for the entity to update the rotation once per second. It shows the same behavior, with it rotating in 5.14.0 and no longer rotating in 5.15.1. I tested in Minetest Game, but as it has no dependencies it should work testing with any game in theory.

https://github.com/CryptechTest/minimal_example

[appgurueu]

Thank you very much! I can now reproduce the issue on 5.15.0 and 5.15.1 (but not on 5.14.0, as you said).

This should make a bisect possible.

The good news is that somehow, on 5.16-dev, everything works again :p

I'll investigate it to make sure it works reliably.