The Liquid FX Modifier is the counterpart to the Liquid FX Emitter. While the emitter derives spray, foam, and bubbles automatically from the movement of a liquid simulation, the modifier converts existing particles directly into Liquid FX particles. Its settings correspond to those on the Properties tab of the Liquid FX Emitter, supplemented by the links to the three Particle Groups for spray, foam, and bubbles. Settings for the emission itself are not needed, because the number of Liquid FX particles results from the particles the modifier processes. This gives you precise control over where and when spray, foam, and bubbles appear.

If the modifier is placed under a Particle Group in the Object Manager, it affects the particles of this group. If it is placed on the same hierarchy level as other Particle Groups, it affects all of these groups within the same Simulation Scene. Placed under a Multi Group, it affects the particles of all groups combined there. With its Mode setting, it can be used in three ways:

• Enable: Standard particles are converted into Liquid FX particles with spray, foam, and bubble properties. Note that standard particles do not have physical properties such as mass or collision detection by default and do not react to gravity automatically. After the conversion, they behave like spray, foam, or bubbles.
• Set Properties: Changes the spray, foam, and bubble properties of particles that are already Liquid FX particles. The new values remain stored on the particles, even if they later switch to another type.
• Disable: Converts Liquid FX particles back into standard particles. If these particles are to continue moving, you may need to add the required properties again with other particle modifiers.

The principle is the same as for the Liquify modifier, which converts standard particles into liquid particles and back.

Converted particles do not keep a fixed type. Like all Liquid FX particles, they are classified anew on every frame based on the number of surrounding liquid particles: Few neighbors result in spray, many neighbors in bubbles, and values in between in foam. A liquid simulation must therefore be present in the same Simulation Scene. Newly converted particles are always classified as spray in the first frame and receive the type that matches their surroundings from the next frame on. As a result, the position at which you emit the particles largely determines which type you get. You can find more about this in the introduction to Liquid FX.

Examples of Use

Rising bubbles in a glass: Place a Basic Emitter at the bottom of a glass filled with liquid and let it emit particles without speed. Place a Liquid FX Modifier in the Enable mode under the Particle Group of this emitter. Since the particles are created inside the liquid, almost all of them turn into bubbles. They rise due to their Buoyancy and turn into foam when they reach the surface, where they collect. With the rate of the emitter, you control exactly how many bubbles rise.

Individual properties for some of the particles: A Liquid FX Modifier in the Set Properties mode can give the particles of a single group different properties. If you place it under the Bubbles group, for example, and increase the Surface Offset of the foam there, all foam created from these bubbles later floats higher above the liquid surface, because the changed value remains stored on the particles. Since particles can switch between spray, foam, and bubbles at any time, keep in mind that the changed values then also apply in their new group.