Skeleton Binary files are best used to improve load times but you need to re-export them every time Spine has a major feature update, as this can cause the binary format to change.
Obviously, binary files are also non-human readable and make it harder to see changes/diffs if you have your project under version control.
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To import or use Skeleton binary files instead of json in Spine-Unity, you need to export in the binary format from Spine.
Note that Unity (as of Unity 5.6) does not recognize arbitrary file extensions.
So you need to change the extension to .skel.bytes
. (Unity will not recognize a .skel
file.)
Spine-Unity will recognize and attempt to auto-generate a SkeletonData asset from it similar to json files.
However, when updating an existing SkeletonData asset, you can to drag the binary .skel.bytes asset into the SkeletonJson field of the SkeletonData asset.