This is an explanation of the restrictions on items that can be used as accessories.
In order for an item to be usable as an accessory, the following restrictions must be met.
Restrictions as accessories
Accessories must have an Accessory Item component.
All elements of Default Attach Offset Position must be between -2 and 2.
Restrictions as items
Item component must be set.
Item Name must be 64 characters or less.
Size of Item must be between 0 and 2 for all elements.
Limitations of GameObjects
Items must contain no more than 128 GameObjects.
All GameObjects contained in the item must have different names.
The item’s GameObject must be active.
All meshes should be triangular. (In the case of general asset formats, assets containing quadrilateral meshes can also be automatically converted to triangular meshes for use. Make sure that Keep Quads is set to false in the asset Import Settings.)
The number of triangles in the mesh must be between 1 and 2000.
The number of sub-meshes in one mesh should be 2 or less.
The mesh should not contain weights.
The area where the mesh resides must be within (2, 2, 2).
Items must contain no more than 8 different meshes.
Items must contain no more than two types of materials.
MToon Shaders can only be used.
An item must contain no more than three textures.
All textures must be in png or jpg format.
All textures must be 8192 pixels or less on each side.
The size of the final uploaded item must be 25MB or less.
Accessories may only use the components listed below.
Components involved in drawing
MeshRenderer, MeshFilter is available.
Item must have at least one active MeshRenderer.
The number of MeshRenderers in one item should be 8 or less.
MeshRenderer settings are only used for Materials.
The range in which the mesh exists must be within (2, 2, 2).