Conventional methods to create fluid animation primarily resort to physically based simulation via numerical integration, whose performance is dominantly hindered by large amount of numerical calculation and low efficiency. Alternatively, video-based methods could easily reconstruct fluid surfaces from videos, yet they are not able to realize two-way dynamic interaction with their surrounding environment in a physically correct manner. In this paper, we propose a hybrid method that combines video-based fluid surface reconstruction and popular fluid animation models to compute and re-animate fluid surface. First, the fluid surface’s height field corresponding to each video frame is estimated by using the shape-from-shading method. After denoising, hole-filling, and smoothing operations, the height field is utilized to calculate the velocity field, where the shallow water model is adopted. Then we treat the height field and velocity field as real data to drive the simulation. Still, only one layer of surface particles is not capable of driving the smoothed particle hydrodynamics (SPH) system. The surface particles (including 3D position and its velocity) are then employed to guide the spatial sampling of the entire volume underneath. Second, the volume particles corresponding to each video frame are imported into the SPH system to couple with other possible types of particles (used to define interacting objects), whose movement is dictated by the direct forcing method, and fluid particles’ geometry information is then corrected by both physical models and real video data. The resulting animation approximates the reconstruction surface from the input video, and new physically based coupling behaviors are also appended. We document our system’s detailed implementation and showcase visual performance across a wide range of scenes.
['Chao Wang', 'Changbo Wang', 'Hong Qin', 'Tai-you Zhang']
Video-based fluid reconstruction and its coupling with SPH simulation