Rendering liquids, especially thin liquid layers, could sometimes show flickering, jittering or popping of the liquid surface in animation.

There are several options you can use to eliminate such artifacts.

Grid Resolution


First, make sure your Grid Resolution is not too low. If you have a simulation with less than 10 milliоn voxels, the flickering might be resolved by increasing the grid resolution and simulating again.

Render-time Solutions


There are also many ways to reduce or completely resolve such flickering after the simulation is done, without having to simulate all over again.

You can combine them and this will make them more effective as well.

Some of these work only for Mesh Render Mode, others work only in Isosurface Render Mode, and some work in both:

Isosurface Level

Changing the Isosurface Level would help when in animation you see many pairs of droplets that keep connecting and disconnecting from one another.

With a different Isosurface Level such pairs will remain always connected or always disconnected.

Note that if you go with too low or too high Isosurface Level, the liquid will either shrink too much or the opposite - gain too much volume and become too chunky.

Isosurface Sampler

Changing the Isosurface Sampler from Linear to Spherical can help in case after switching from Mesh to Isosurface mode, some droplets don't look round enough and are still somewhat edgy.

This will smooth these droplets additionally at the expense of some rendering slowdown.

Grid Channel Smoothing

Input Grid Channel Smoothing will work for both Isosurface and Mesh modes in order to reduce flickering in animation.

During FLIP simulation, particles get voxelized to a grid when a cache file is saved, and when the liquid surface is created, this voxel grid is used.

This is why smoothing the grid data of the Liquid/Temperature channel will help in turn to smooth out the surface of the liquid.

The recommended values for the smoothest result are all zeroes for the ThresholdSimilarity and Random Variation options - this will produce strongest smoothing, evenly applied over the entire liquid grid, without adding any random variation.

Mesh Smoothing

When rendering in Mesh mode, you have additional control allowing you to smooth out the produced mesh surface.

Simply increasing the Mesh Smoothness will even out rough edges of the mesh, and optionally, for FLIP liquid simulations, you can enable the Use Liquid Particles for Smoothing option.

It will involve the liquid particles in the mesh construction, in addition to the mandatory Grid Liquid channel, and thus will both improve the smoothing even more, and will also allow you to shrink or inflate the sizes of the liquid droplets inside the mesh.

This can also improve any flickering in animation. Note that Mesh Smoothness can be used together with Input Grid Channel Smoothing.

Relax modifier

An additional tool you can use for further smoothing the mesh surface would be the 3ds Max Relax modifier. It can also be combined with Grid Channel Smoothing and Mesh Smoothing.

Table of Contents