A smart space simulation is cost-effective means to analyze human activities and design and test human-centered intelligence in real smart spaces. A powerful smart space simulator not only synthesizes sensor data, but also generates highly realistic activity visualizations that serve as immediate visual feedback for the simulation user to validate her/his simulation design. In this paper, we present our approach for creating highly realistic simulation and visualization of activities of daily living (ADL) in smart homes within our Persim 3D simulator. We design and compile a set of ADLs into Persim3D activity library. We present three simulation models for human actions and space objects (necessary for performing and visualizing the activities), and sensors (necessary for sensing the effect of interactions between the virtual character performing the activity and the virtual space). We evaluate Persim 3D’s simulation fidelity through use study, by gauging users’ perception of the realism of activity visualization. © 2017, Springer International Publishing AG.