Building Physical 3D Models

Abstract

Fig. 3.1: A CNC routed model of the Sonoma Valley, California Tangible Landscape works with many types of physical 3D models. When used as a continuous shape display the physical model should be built of a malleable material such as sand, clay, or wax so that users can easily deform the surface. When used for object recognition the physical model can be built of a rigid material such as a wood product, plastic, or resin. When both modes of interaction are combined the physical model should use malleable materials for the base and rigid materials for the objects. These models can be built by hand or digitally fabricated using 3D printing or computer numerically controlled (CNC) manufacturing. The final model should be opaque, have a light color, and have a matte finish so that the projected image is crisp and vivid. Transparent materials like acrylic cannot be 3D scanned with a Kinect. Some 3D printing and cast-ing materials like resin may appear opaque, but have translucent properties – this will diffuse the projection. If we desire a very crisp and vivid image on 33 34 3 Building physical 3D models a rigid model made of wood products or resins we recommend painting the model white. In this chapter we discuss different types of physical models and explain how to fabricate them. 3.1 Handmade models Fig. 3.2: Sculpting a polymeric sand model Rigid physical models can be handmade by hand-cutting contours and malleable physical models can be handmade by sculpting sand or clay. Contour models can be precise if they are finely cut, but they are inaccu-rate as they depict abstract, stepped landscapes that are discrete rather than continuous. They are also very legible – one can easily count the contours and read the height – but again they represent abstracted landscapes. While one can easily read the contours and then calculate slope, it is hard to intuitively visualize the slope. Furthermore this abstract, discontinuous representation may obfuscate the relationship between form and process. Furthermore they are time consuming and complicated to construct especially for complex to-pographies. Hand cutting contour models can be dangerous as the knife may slip or jump. Contour models can be made out of stacked boards of paperboard, card-board, foam, or a soft wood like balsa or basswood. The thickness of the