• Unity

  • Can't get Bone position

Hey, I'm just trying to get that hand position but can't get it right.

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Here's what I do:

Spine.Bone bone = anim.getBone("hand2"); // the bone is retrieved properly (checked)
Vector3 local = new Vector2(bone.X, bone.Y);
Vector3 world = new Vector2(bone.WorldX, bone.WorldY);

Two red dots are spawned at local, world. Two other at local+hero.transform and world+hero.transform just to check. None match the hand2 actual position... :wonder:

Any leads?

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First, a quick description of Spine's spaces (and terminology for them):
a bone's "local" properties (rotation, x, y, scaleX, scaleY...) are within its immediate parent's space (with rotation applied first so position is in parent's space rotated according to rotation).
a bone's "world" properties (WorldX, WorldY, WorldRotationX...) are relative to the Skeleton's/Spine's world space, which is its (0,0) point, x-right, y-up axes and a uniform scale of 1.

In Unity, the render is affected by the Spine GameObject's transformation— a Spine.Bone's "world space" is as described above, but the resulting mesh is transformed according to the Spine GameObject's Transform's resulting space. So scaling, rotating and moving your Spine GameObject around results in the render's "Unity World" values that would not be the same as the "Spine World" values.
In other words, the "Spine World" value is actually a local value of the Spine GameObject Transform.

If there was no scaling or rotation, a simple addition would suffice: (new Vector3(bone.WorldX, bone.WorldY) + transform.position). But if a bunch of transformations were passed to it in the hierarchy, that simple addition would stop being correct.

For the most part, a reliable way to get a "Unity World" position from a "Spine World" position is with Transform.TransformPoint:

Spine.Bone bone = mySkeleton.FindBone("hand2");
Vector3 unityWorldPosition = skeletonAnimation.transform.TransformPoint(new Vector3(bone.WorldX, bone.WorldY, 0f));

TransformPoint uses the Transform's internal matrix to convert the Vector into a world position.

So you don't have to memorize that, we actually made that extension method a while back: https://github.com/EsotericSoftware/spine-runtimes/blob/master/spine-unity/Assets/spine-unity/SkeletonExtensions.cs#L106-L108
So you only need to say:

Spine.Bone bone = skeletonAnimation.skeleton.FindBone("hand2");
Vector3 unityWorldPosition = bone.GetWorldPosition(skeletonAnimation.transform);

Oh jeez, I'm glad I asked this silly question 'cause I wouldn't have figure that out. Thanks!

Thats's useful information indeed. Can you put that somewhere in a more central place so people don't have to read all the forum posts for sth like this? 🙂

4 days later

I regularly update the spine-unity documentation when I feel like some generally useful questions were asked in the forum, and where I feel there's a comprehensive answer for it to give it better context.