Abstract
The challenges of geometric representation for Additive Manufacturing (AM) are many. Material properties can vary through the object, lattice structure and internal voids are used for improving performance. State-of-the-art CAD-tools are not well suited for AM as they are b-rep based: An object is represented by its inner and outer hulls. b-rep representation was developed more than 3 decades ago targeting design for subtractive/abrasive manufacturing. IsoGeometric Analysis (IGA) [Hughes 2005] bridge the gap between CAD and Finite Element Analysis. The shape functions in FEM are replaced by B-splines, allowing higher order continuity between elements and accurate shape representation. However, going from b-rep CAD models to 3-variate B-spline based IGA models is as complex as meshing CAD-models. Thus, research started addressing 3-variate spline based CAD-models that can be used directly in IGA [EC FoF project www.caxman.eu]. Continuously varying properties inside an object can be represented by additional spline functions connected to the geometry through a shared parametrization. For objects to be built from multi materials, is easy to see that such fields can be used for specifying the material mixture imitating RGB in colour representation. However, these fields also have a potential to be used as parameters for procedural generation of lattice structures: Required density; required geometry or property anisotropy, etc.