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A well-formed shape is defined as a shape that is complete and without abberation. For example, a rubber-band stretched in the shape of a rectangle is well-formed. However, a set of four lines meeting at four corners may not be considered as a well-formed shape. For example, a set of four matchsticks put together in the shape of a rectangle does not create a well-formed shape, even if the corners are glued together.

A typical CAD software has shapes built out of elements like points and lines. These are called ill-formed shapes. Likewise, when a shape is extruded to form a volume, it can either be a well-formed object or not.

A typical surface modeling software has objects that are ill-formed. Multiple ill-formed shapes come together to form the faces of the volume (object). In case of solid modeling software, if the geometry of the object can further be sub-divided into further geometrical shapes and elements, then the objects are considered as ill-formed objects. However, if the objects in the solid modeling software are holistic in nature and cannot be further geometrically sub-divided, they are considered as well-formed objects.

A well-formed shape is a complete, holistic shape. For example, a rubber-band stretched in the shape of a rectangle is a well-formed shape. However, a set of four lines meeting at four corners are not considered as a well-formed shape. For example, a set of four matchsticks put together in the shape of a rectangle does not create a well-formed shape, even if the corners are glued together.

In CAD software, shapes are built out of elements like points and lines. Such shapes are ill-formed shapes. Similarly, when a shape is extruded to form a volume, it can either be a well-formed object or not. Multiple ill-formed shapes come together to form the faces of the volume. In solid modeling software, if an object can further be subdivided into other geometrical shapes and elements, the objects are considered as ill-formed objects. However, the objects in the solid modeling software are holistic in nature and cannot be subdivided further geometrically. Therefore, these shapes are considered as well-formed objects.