This property determines whether to render both faces or polygons in the mesh. It is only changeable in Studio. This is useful for meshes that are typically modeled as cards such as a leaf, hair and cloth.
The tree leaves are modeled with single sided cards.
With MeshPart.DoubleSided disabled some leaves are missing since they are back facing the camera.
With MeshPart.DoubleSided enabled, both faces of the leaves are rendered.