Implicit Field-Based Stylization of 2D and 3D Liquid Animations

Combining physically-based simulation with stylized visual effects not only requires to change the aspect of surfaces, but their shapes as well. We describe a new expressive rendering method for liquid animations, which can be used on top of any preexisting particle-based simulation. Our solution builds on visual particles that carry both water and air distributions, both evolving through particle history based on kinematics information from the simulation. These density fields are combined at each frame to create the implicit iso-surface of interest, rendered in adapted style. By defining series of visual particle states, we parametrize this model to capture the typical stylized geometry of water bodies used to highlight dynamic motion in paintings and cartoons, such as elongating droplets, concavities carved at the crest of breaking waves, and stylized air-water mixtures such as bubbles and foam. Regardless of the 2D or 3D nature of the input simulation, our solution maintains temporal coherence and ensures that water bodies keep an approximately constant surface in 2D, resp. or volume in 3D, over time. Finally, we conducted a user study to show the effectiveness of our method against state of the art AI-based tools, in a variety of animation scenarios where stylized shapes are needed.