Regarding Problem C, we also apply the guideline of level
3 First Focus: if the user clicks on a ceramic group, the
interface emphasizes this group, leaving the rest of the
interface elements in the background. In Fig. 2, if the user
would like to focus on the group of decorated pots with balloon
shape, the system will disable with a grey background all the
elements of the interface except for the black sphere. Thus, the
interface shows the same set of information, but with an
additional emphasis on a particular area.