The best way to get started with modeling your building is to set up your drawing units. AutoCAD and Radiance are both "unitless" modeling systems. This means the "size" of a unit of distance is defined by the user and implemented as a convention. Sometimes a scaling factor is also used which causes the unit to be proportionately larger or smaller than its base unit size. These settings for your drawing can be defined in the Preferences Dialog Box see Preferences Preferences. Once you have set up the units you are ready to start modeling and making attachments from the Radiance menu. Below we will discuss each menu item in turn starting with the Materials menu item.