Three-dimensional objects can be covered by copyright as artistic works. As with other types of works, there is no requirement for artistic merit, so copyright can apply to the appearance of any type of object as long as it is original.
However, there is a separate type of protection for the appearance of mass-produced items, provided by design registration. Accordingly, once a three-dimensional object has been mass-produced it is no longer a copyright infringement for someone to copy it, regardless of whether it has been registered as a design.
Thus if you want protection for your original three-dimensional design, you have to apply for a registration under the Designs Act, and your protection will expire after 10 years.
A special exception to the rule is a building or model of a building. Buildings continue to be protected by copyright even after many copies have been built, provided that they are not registered as designs.
A similar exception applies for works of artistic craftsmanship. These must have an artistic quality and they must involve craftsmanship.
Items of clothing and dressmaking patterns normally do not qualify as works of artistic craftsmanship because they are not intended primarily as works of art. Hand-made pottery and woodwork items may qualify.
It is important to decide whether an item is a work of artistic craftsmanship before making it public or offering it for sale.
If it is not a work of artistic craftsmanship, the only effective form of protection is design registration, and you will not be able to get a valid design registration if your design has been made public before your design application is filed.
If it is a work of artistic craftsmanship, you will want to avoid design registration altogether so that you can keep your copyright protection.