Temporal Foveated Fluid Animation in Virtual Reality

Simulating realistic fluids in virtual reality (VR) is computationally demanding, often limiting the scale and complexity of immersive environments. Existing foveated fluid simulation approaches primarily focus on spatial adaptivity. In this paper, we introduce a gaze-contingent fluid simulation system from a temporal perspective. We conduct a perceptual study to quantify the relationship between gaze eccentricity, fluid density deviation, and the perceptual threshold for simulation timesteps. Based on these findings, we fit a perceptual model that predicts the timestep requirements for maintaining perceptual realism in VR fluid animation. To exploit this model, we propose an asynchronous position-based fluids (PBF) algorithm that assigns fluid particles different local timesteps according to their visual importance and density deviation, ensuring both physical stability and perceptual validity. Our solver performs high-frequency updates in perceptually critical regions while progressively reducing updates elsewhere. A validation user study shows that our method remains perceptually indistinguishable from a high-fidelity, uniform-timestep PBF simulation. Objective evaluations further confirm that our approach improves efficiency while maintaining perceptual quality. Runtime experiments demonstrate speed-ups of up to 1.52× across diverse fluid scenarios, enabling more complex and larger-scale fluid phenomena in real-time VR. Our findings extend the paradigm of foveated fluid animation into the temporal domain, providing a perceptually grounded framework for fluid simulation in VR.