Architecture cannot divorce itself from drawing, no matter how impressive the technology gets. Drawings are not just end products: they are part of the thought process of architectural design. Drawings express the interaction of our minds, eyes and hands. This last statement is absolutely crucial to the difference between those who draw to conceptualize architecture and those who use the computer.

Of course, in some sense drawing can’t be dead: there is a vast market for the original work of respected architects. I have had several one-man shows in galleries and museums in New York and elsewhere, and my drawings can be found in the collections of the Metropolitan Museum of Art, the Museum of Modern Art and the Cooper-Hewitt.

But can the value of drawings be simply that of a collector’s artifact or a pretty picture? No. I have a real purpose in making each drawing, either to remember something or to study something. Each one is part of a process and not an end in itself. I’m personally fascinated not just by what architects choose to draw but also by what they choose not to draw.

For decades I have argued that architectural drawing can be divided into three types, which I call the “referential sketch,” the “preparatory study” and the “definitive drawing.” The definitive drawing, the final and most developed of the three, is almost universally produced on the computer nowadays, and that is appropriate. But what about the other two? What is their value in the creative process? What can they teach us?