Animations appear correct in Spine editor, but are broken when imported in Unity

leonardopalmerummi

Dear Spine Support Team,

I’m using Spine 4.2.43 Professional and I’m encountering a serious issue when exporting animations to Unity.

In the Spine editor, all animations look correct — including those using IK constraints. However, once I export the project (JSON, Atlas, PNG) and import it into Unity (using the official Spine-Unity runtime), several animations appear broken.

In particular, bones that were controlled by IK in Spine seem to be in incorrect positions or orientations in Unity, even though they work perfectly in Spine. It looks like Unity does not reproduce the IK results properly at runtime, even when using the latest runtime.

I understand IK constraints need to be baked before exporting, but I’m working with a large number of animations, and manually baking each one is time-consuming and error-prone. Moreover, some constraints do not appear to bake properly, or the "Bake Constraint" option is greyed out even when selecting the constraint in the timeline.

Could you please clarify:

The correct workflow for ensuring IK-based animations export and play correctly in Unity?

If there is an automated way to bake all constraints across all animations?

Why the exported data differs from what I see in the Spine editor?

I’d greatly appreciate any help or documentation reference that could assist me in solving this problem, as it’s blocking my integration pipeline.

Thank you for your support and for the great tool!

Best regards,
Leonard

Spinebot

To ensure that IK-based animations export and play correctly in Unity, you should follow a few key steps. First, make sure you are using compatible versions of the Spine editor and the spine-unity runtime. For example, if you are using Spine 4.2.43, ensure that your spine-unity runtime is compatible with this version. When exporting, consider using the binary format (.skel.bytes) instead of JSON, as it can sometimes avoid issues related to data interpretation in Unity. Regarding baking IK constraints, while it is generally recommended to bake them for better performance and compatibility, if the "Bake Constraint" option is greyed out, it might be due to the specific setup of your constraints or the version of Spine you are using. Unfortunately, there isn't a built-in automated way to bake all constraints across all animations in Spine, so it might require manual intervention or scripting within Spine to automate this process. Lastly, discrepancies between the Spine editor and Unity can often be attributed to differences in how the runtimes handle certain features, so ensuring that your export and import settings are correctly matched is crucial.