Efficient rendering and simulation of fluid transport and phase transitions in SPH-based fluids

Particle based fluid simulation using the smoothed particle hydrodynamics (SPH) method has gained much attention in recent years. Due to its flexible discretization, inherent mass preservation and its ability to stably simulate free surface flows and complex interactions with boundaries, SPH has found its way into many fields of research. While many phenomena including the transport of substances such as salt or dye, and melting and solidification can already be described in SPH, interactions with the air phase are commonly omitted. Typically, SPH liquids are rendered only in terms of their surface. However, with the growing complexity of simulations there arises a need for complementary rendering and visualization techniques that take transport of substances into account. The goal of this work is to improve fluid animation of surface dynamics and the rendering and visualization of fluid transport.
First, a simulation of evaporation and condensation of SPH based fluids is introduced. Therefore, the air phase is simulated on a coarse grid and exchanges mass with the particle based liquid phase. Condensation only takes place on surfaces of rigid objects and is realized using textures into which mass can be condensed and from which particles can be generated. In order to achieve high visual detail of condensed liquids at surfaces, an implicit surface model is developed that allows to render moving liquid droplets at sub-particle detail including dynamic contact angles.
Second, an efficient adaptive volume ray casting of SPH-based scalar fields is developed. In order to achieve fast spatial access to particle data, particles are mapped to cells of a view-aligned perspective grid. By applying a sampling error analysis to the volume rendering equation inside of each grid cell, the sampling rate can locally be adjusted according to a user-defined screen space error tolerance yielding substantial speedups without sacrificing image quality.
Third, this work presents a vector field visualization of advective-diffusive flows of scalar quantities. Therefore, the advective, diffusive and total flow are each decomposed into a scalar quantity and a velocity component of transport. By introducing the novel visual metaphor of stream feathers, all flow components can be simultaneously visualized allowing for an intuitive insight into complex flow scenarios.