  We introduce Blocks, a mobile application that enables people to co-create AR
structures that persist in the physical environment. Using Blocks, end users
can collaborate synchronously or asynchronously, whether they are colocated or
remote. Additionally, the AR structures can be tied to a physical location or
can be accessed from anywhere. We evaluated how people used Blocks through a
series of lab and field deployment studies with over 160 participants, and
explored the interplay between two collaborative dimensions: space and time. We
found that participants preferred creating structures synchronously with
colocated collaborators. Additionally, they were most active when they created
structures that were not restricted by time or place. Unlike most of today's AR
experiences, which focus on content consumption, this work outlines new design
opportunities for persistent and collaborative AR experiences that empower
anyone to collaborate and create AR content.
