"Hydnum" is an extended reality data-driven interactive installation that immerses the visitor in a transmodal continuum of scent, music, form, poetry, space, and light. This data-driven piece is based on research connecting virtual and physical elements to emotional affect and cross-sensory stimulus through human biodata. Hydnum extends James Russell's "Circumplex Model of Affect and Motivational State" into transmodal worldmaking in extended reality.

The motivation for exploring this field lies in the investigation of cross-sensory relationships between different mediums. A wide range of virtual and physical spaces could potentially benefit from these kinds of explorations, considering the impact of olfactory stimuli on human experience and the perception of a place. This research explores the relationship between Extended Reality and Biodata.

Hydnum is a transmodal / symbiotic system consisting of a prototype medical scent delivery system, a cyber-physical artifact, an extended reality experience, and a generative audio component. The biodata visualizations also extend into the surrounding area by using projection mapping. The interactive spatial system can transmit scents based on the user's real-time psychophysiological measures (heart rate and heart rate variability data).

A modular system of tubes, 3D printed outputs, and brackets emerge from the six scent modules of the BIOPAC modular scent delivery system and expand into the surrounding space, introducing a prominent tree-shaped structure. Our approach adopts the characteristics of a nonlinear network, usually referred to as "Rhizome" after the Ancient Greek word "ῥίζωμα", "rhízōma".

Hydnum is the result of the ongoing collaboration between the transLAB, BIOPAC systems, and SBCAST (Santa Barbara Center for Art, Science, and Technology).