nxFoam

Overview Video

nxFoam analyzes fluid data and, from that data, generates bubbles, foam and spray particles.

Object Properties

Emitter

Drag and drop an xpEmitter into this field to spawn foam particles.

Add Emitter

Click this button to create a new spawning xpEmitter and add it to the Emitter link field.

This emitter will then be used to create the foam particles.

Emission

These settings govern how and when the particles are created.

Crest Rate

This is the spawn rate (which can be fractional) for particles created at the crest of waves, using the Min Crest and Max Crest settings.

This is set at 5, by default.

Animation to show foam particles generated from a Crest Rate of 30, using a narrow crest curvature between a Min Crest of 90% and a Max Crest of 95%.

Air Rate

The spawn rate for foam particles created as trapped air between colliding fluid particles (controlled with the Min Impact and Max Impact settings).

In this animation, foam particles are being generated from an Air Rate of 30, with a Min Impact setting of 0 (zero) and a Max Impact of 1.

After Age

Only those fluid particles which are older than this setting will create foam particles.

This enables an xpEmitter to fill or flow before creating the foam particles (otherwise, on emission, foam particles would be created immediately).

The default setting is at 60 frames.

Animation showing foam particles generated after the fluid particle After Age setting of 60 frames.

Variation

Adds some variation to the After Age setting for each particle so that not all foam is created at the same time.

This animation has foam particles generated after the fluid particle After Age setting of 20 frames, with a Variation value of 100%.

Life

Controls the lifespan of the foam particles.

Animation demonstrating an increased foam particle Life setting of 300 frames, allowing particles to remain throughout the simulation.

Variation

Adds some variation to the life of the foam particles so that they don't all disappear at once.

Radius

This parameter controls the spawning radius, the radius of the sphere around each fluid particle that creates foam.

It is set at 10%, by default, which is the recommended setting.

On the left, a Radius of 20% and, right, a Radius of 400%, creating foam within a wider area around the water particles.

Surface

This parameter controls the smoothing radius used to calculate the fluid surface.

At 100% it matches that used by the fluid solver, but at this value the foam may be located too far away from the meshed surface.

At around 50% (the default setting) the fluid surface is closer to the mesh and gives better results for the foam offset from the surface.

In this animation, the foam particles’ position is being offset by changing the Surface value.

Min Speed/Max Speed

The speed range (cm per second) needed by the fluid particles to create the foam particles.

The highest speed (and most energetic) fluid particles of your simulation should be set to create foam particles.

Animation demonstrating lowering the Min Speed and Max Speed values, allowing foam particles to be generated from slow moving water particles.

Min Crest/Max Crest

These settings represent the percentage of curvature of the wave crest needed to create foam particles.

A low value implies something flat (which would not realistically create spray) and high values something like a wave curving back on itself.

Mid-range values are more natural.

This image compares flat and peak foam particle emission based on the wave curvature Min Crest and Max Crest settings.

Min Impact/Max Impact

The impact speeds between particles needed to trap air and generate foam (used for the Air Rate emissions).

Animation illustrating how lowering the Max Impact Value increases the amount of air particles created from water particles.

Advection

These settings control how the particles are moved by the fluid, once they are emitted.

Buoyancy

The Buoyancy setting is the force with which the particles resist the effect of gravity.

The lower this value, the more likely it is that particles will sink below the surface of the fluid.

At higher levels, more of these particles will float to the surface.

This animation demonstrates the reduction of the Buoyancy effect on foam particles, from 50% to 0 (zero) %.

Drag

This controls how much the fluid drags the foam/air particles around, but does not affect spray.

In this animation, the Drag value is lowered from 70% to 0 (zero) %, then raised up to 100%.

Gravity

Drag and drop a gravity modifier into this link to specify which modifier to use.

Otherwise the fluid object will use the first gravity modifier it finds when evaluating modifiers for this emitter.

Note: This is used for buoyancy, the opposite to gravity direction.

Spray

On creation of the particles, this controls how much random velocity is given to them to spray them away from the creation point.

Rotation

If this is set, the foam particles are given a rotation, which is then aligned (Y-axis) to the fluid surface (when near the surface).

Here, foam particles are represented as arrows with Rotation set to 100%.

Foam Density/Spray Density

The surrounding fluid density, below which particles are considered to be spray or foam.

Groups Affected tab

Groups

To specify the group, drag and drop the desired Group object into this field.

This setting is useful if you want to ensure that the spawned particles are, or are not, affected by nxFoam.

Mapping tab

The modifier’s settings can be mapped to particle data.

Use the dedicated manual page, below, for instructions on how this works.

Mapping

Fields tab

You can use the Fields options to control where nxFoam operates.

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