When designing interactive architectural systems and environments, the ability to gather user feedback in real tme provides valuable insight into how the system is received and ultmately performs. However, physically testng or simulatng user behavior with an interactive system outside of the actual context of use can be challenging due to tme constraints and assumptions that do not reflect accurate social, behavioral, or environmental conditions. Employing evidence-based, user-centered design practces from the field of human-computer interaction (HCI) coupled with emerging architectural design methodologies creates new opportunites for achieving optmal system performance and design usability for interactive architectural systems. This paper presents a methodology for developing a mixed reality computational workflow combining 3D depth sensing and virtual reality (VR) to enable iterative user-centered design. Using an interactive museum installation as a case study, user pointcloud data is observed via VR at full scale and in real tme for a new design feedback experience. Through this method, the designer is able to virtually position him/herself among the museum installation visitors in order to observe their actual behaviors in context and iteratively make modifications instantaneously. In essence, the designer and user effectively share the same prototypical design space in different realites. Experimental deployment and preliminary results of the shared reality workflow are presented to demonstrate the viability of the method for the museum installation case study and for future interactive architectural design applications. Contributions to computational design, technical challenges, and ethical considerations are discussed for future work.