The ZEPETO rig is set up in Maya, and uses Maya's default joint orientations. In Maya, joint chains can be aligned to any axis, whereas in Blender, bones are strictly pointed along the Y-axis. While it may look strange, for compatibility with the ZEPETO avatar, it is important to not change the bone orientation of default bones.

Blender doesn't support binding meshes to a posed armature in the armature's non-rest pose. When binding weights to the armature, use an armature applied at the desired rest pose in pose mode or a duplicate rig with an A-pose set as the rest pose.

Rigging is the process of applying the data to make an item move with the ZEPETO avatar. Without rigging, an item won’t move with the avatar in the app. Through the process of rigging, we’ll tell our item how to follow the avatar’s skeleton. More technically: In 3D applications, the 3D geometry of a character is often controlled by joints or bones. These joints or bones are special 3D objects that don't show up in rendering that set rules for how a character will move, often serving as pivot points. Rigging is the process of saving data that tells a mesh's vertices how closely they should follow a given joint or bone. In Blender, this type of data are called "vertex groups." Weights can be numerically assigned or "painted" onto a model. As virtually painting on influence is more approachable than assigning decimal numbers to individual vertices, we'll be focusing on this method of weight painting to save time and sanity. Joints and bones serve similar functional purposes in 3D software, with slight differences that go along with their terminology. Joints represent a single point in 3D space with no software-defined preferred directions. Maya uses joints and generally tends to align joints with their X-axes pointing to the next bone on the chain. Bones functionally also represent a single point in space, but have software-defined directions that it expects other characters to follow. Blender uses bones, with their Y-axes designed to point to the next bone on the chain. This difference between bones and joints creates a few issues in how the rig is handled in Blender that we need to work around.

Generally, dresses use the bones of the upper and the lower sections of the rig, while other items have a more constrained selections. The mask object that comes with the Creator Base Set has the weights from the ZEPETO avatar. It's useful to use the weights from the mask object as a basis for weighting items. To transfer the mask weights to the item's weights, use Blender's Weight Transfer functionality.

Use the mask and armature objects included in the creatorBaseSet_zepeto.fbx file. These objects have a defined set of object names, bone names, and bone orientations that ZEPETO studio will look for to make an item work in the app. It's important to keep the names similar to not confuse the conversion process later in Unity.

Blender applies its initial weighting data to an armature’s “rest pose.” This means that if you modeled items in an A-pose and try applying it to a T-pose rest pose armature, the item may shift out of the correct position in the initial binding operation. To get around this issue, it is useful to bind the item to an armature that has its rest pose set to the item’s modeled pose. A useful method to having a non-T-pose rest posed armature is to create a duplicate of the original armature and mask, applying the rest pose to the newly duplicated armature, and rigging the clothing item based on the rest pose. For organizational purposes, the duplicated mask and rig should be renamed based on their new pose. Putting each armature and mask set in their own collections can also help with organization. Applying a rest pose to the armature is relatively simple:

3. Select the armature element and go to Pose Mode



4. Return to object mode and select the mask element

Now the armature has a new rest pose applied to it and the mask element will follow this new rest pose.

Use the mask and armature objects included in the creatorBaseSet_zepeto.fbx file. These objects have a defined set of object names, bone names, and bone orientations that ZEPETO studio will look for to make an item work in the app. It's important to keep the names similar to not confuse the conversion process later in Unity.

5. Transfer the weights of the mask to the item

6. Rotate joints to check if the weights on the item are set properly

Blender’s symmetry and bone naming system prevents the provided rig from having easily mirrored vertex groups using built-in weight mirroring tools. Weight symmetry has to be manually applied or mirrored via an add-on.

Rigging skirt elements requires some additional attention. Skirts are more challenging to rig in ZEPETO due to the standard behavior of anything with leg elements. Skirts will follow the legs of an item like an expanded set of pants. This can lead to the middle section of the skirt stretching when the legs are moved apart. This is unavoidable, but through some careful weight painting, the stretching can be smoothed out.

When the rigging binding and correction is complete, the rig has to be reverted to the T-pose to export. To do this, we’ll take our item rigged to the A-pose armature and put it into a t-pose, apply the item in the T-pose, and rebind the item to the T-pose skeleton. In more detail:

5. Add an armature modifier to the item

6. Make corrections to the item’s mesh or to the item’s weights for any errors that appear from the weight transfer

Due to how deforming works, meshes moved back into T-pose are likely to lose some volume in the shoulder/upper-arm area on return to T-pose. Editing the mesh to add volume back is a relatively simple fix. Use the T-pose Mask as a reference for mesh boundary areas.

When all weights have been finalized and are ready to export, delete bone sets with no influence on the item. ZEPETO studio limits the number of bones an item can be uploaded with to 100. Deleting unused bones preempts this bone count issue, as Blender’s exporter will export every bone in the skeleton, even if they lack vertex groups or weights. If an item requires many additional bones, it may be necessary to remove non-scale bones to reduce bone count. If required, delete non-scale bones with a corresponding scale bone, except if they are twist bones or the hips bone. The item will break if the hips bone is not included.