A method employs a first polymeric material to deposit first and second pattern layers laterally shifted from each other such that laterally shifted pattern layers form between them an empty volume with a variable cross-section that varies along with the first and second pattern layers. A second polymeric material is cast in the empty volume between the first and second pattern layers to cast a complex-shaped 3D object identical in shape to the empty volume between the first and second pattern layers. Radiation is applied to cure the first and second polymeric materials. The first polymeric material is a water breakable material composition including acrylamide, methacrylamide, acrylate, acrylic acids, and acrylic acid salts, hydroxy(meth)acrylate, carboxy(meth)acrylate, acrylonitrile, carbohydrate monomers, methacrylate and polyfunctional acrylics.