AnimatedModel w/Skeleton not rendered in base pose

I’m importing some custom models into Urho3D using a custom Model implementation (which extends Model and overrides serializing the data from a custom format) and passing this to the standard AnimatedModel class. If I don’t applying a Skeleton to the custom Model, the model is then rendered as I would expect. But as soon as I apply the model’s skeleton, it is no longer rendered or at least visible.

I’m setting the skeleton which consists of 26 bones in total as follows:

Urho3D::Skeleton skeleton;
auto &bones = skeleton.GetModifiableBones();
for (unsigned i = 0u; i < modelFile->GetBones().Size(); ++i)
{
  const auto &modelBone = modelFile->GetBoneByIndex(i);

  Urho3D::Bone bone;
  bone.name_ = Urho3D::ToString("%u", modelBone.boneId);
  bone.nameHash_ = bone.name_;
  bone.initialPosition_ = modelBone.pivot.ToUrho3D();
  // we do not define the following in our bone definitions
  // additionally, bounding box, offset matrix, and radius aren't in the data
  bone.initialRotation_ = Urho3D::Quaternion::IDENTITY;
  bone.initialScale_ = Urho3D::Vector3::ONE;
  bone.parentIndex_ = (modelBone.parentBone == -1 ? i : modelBone.parentBone);

  bones.Push(bone);
  if (bone.parentIndex_ == i)
    skeleton.SetRootBoneIndex(i);
}

// Set the skeleton on the Model
SetSkeleton( skeleton );

I wouldn’t expect that an AnimationTrack needs to be bound to the model because if I disable applying that to the model in the SkeletalAnimation example, the model renders with the skeleton & the base model pose just fine.

Is there potentially something else I need to be setting properly for this to work?

Maybe the bounding box and/or the nodes for the bones? But those may also be set by the skeleton?

From what I can tell from the code, when no skeleton is defined, the boneBoundingBox_ is defined as as the default infinite bounding box. a new bone uses the same infinite bounding box by default, therefore when no collision is being applied, this should all be fine. When no collision mask is being applied, I don’t see where radius_ is necessary either.

Just stepped through the bone creation step and those are being created as I would expect them, with the appropriate parent/child relationships being defined between the bones and the nodes within the scene.

The only questionable part here to me was the Bone’s offsetMatrix_. This gets used when the model calls UpdateSkinning but the default is an identity matrix, so technically this leads to populating the skin matrices by either the constructed bone node’s transform or the model’s depending if a node is yet attached to the bone at the time the method is called, which again should all be fine.

Suffice to say I’m still stumped.