We have developed a multi-user collaborative infrastructure, SCAPE (an acronym for Stereoscopic Collaboration in Augmented and Projective Environments), which is based on recent advancement in head-mounted projective display (HMPD) technology. SCAPE combines the functionalities of an interactive workbench and a room-sized immersive display to concurrently create both exocentric and egocentric perspectives. SCAPE intuitively provides a shared space in which multiple users can simultaneously interact with a 3D synthetic environment from their individual viewpoints, and each user has concurrent access to the environment from multiple perspectives at multiple scales. SCAPE also creates a platform to merge the traditionally separate paradigms of virtual and augmented realities. In this paper, we discuss the design principles we have followed to conceptualize the SCAPE system and briefly summarize SCAPE's hardware implementation. Furthermore, we discuss in detail the high-level design and implementation of the SCAPE architecture, and present a set of unique widget interfaces currently available in our implementation that enable and facilitate interaction and cooperation. Finally, we demonstrate SCAPE's unique visualization and interface capabilities via a testbed application— Aztec Explorer.