UV Mapping
Mapping is an operation that consists of drawing a regular grid directly on the surface. The materials that will be applied to the surfaces in Matter are cut along and positioned in accordance with the grid. If the grid is deformed, the material applied to the surface will present the same deformation.
Most materials are not deformable or support only slight deformations. Consequently, the mapping grids must be regular and only slightly deformed.
 Before mapping. |  Mapping assignment. |  After mapping. |
The Dressing tab 
in the Shaper sidebar contains a panel that shows the tools used for mapping surfaces.
By default, surfaces created in Shaper contain no mapping information. Surfaces without mapping cannot receive material and appear grayed out in Matter.