Scene
Simulation
Grid
Speed
Splashiness
Gravity
Tilt
Splashiness is the FLIP share: high gives lively, splashing water, low a calmer, “thicker” liquid. Tilt turns the direction of gravity as if the tank were tipped.
Look
View
Material
Colour
Absorption
Background
Light
Light height
Exposure
Studio render
Studio mode stops the simulation and path traces the current frame: water refracts light (index 1.33), reflects it following Fresnel, reflects totally from inside and absorbs colours with depth; milk and paint are matte with a sheen, mercury is a mirror. The image gets cleaner with every sample.
Bounces
Light size
Depth of field
Samples
Export
Saves the current view. In Studio mode the image is rendered again at full size with the chosen number of samples.
Size
How it works
The simulation uses FLIP (Fluid Implicit Particle) - the method used by visual-effects software. The liquid is hundreds of thousands of particles, and every step: particle velocities go to a grid (velocities on cell faces), gravity acts, then the pressure is solved (red-black over-relaxation, 30 iterations) to remove divergence - that makes the liquid incompressible. Particles take the velocity change from the grid (FLIP) mixed with the grid velocity (PIC) and move with a Runge-Kutta step. The surface comes from a particle density field at double resolution, blurred and ray traced. Everything runs on the graphics card (WebGL2).