pbd liquid sim

 

This is the main PhysX PBD liquid simulation node where users can define various physical properties. It also controls the creation and behavior of foam particles. Submerged foam particles are referred to as bubbles, while foam particles suspended in the air are known as spray.

 

 

Enable – Disable this node to disable liquid calculations.

 

PhysX Sim - Select the PhysX simulation from which to retrieve joints.

 

Use CCD – This option will enable Continuous Collision Detection for PBD liquid.

 

Pos Iteration - Number of position iterations the solver should perform. Increasing the position iterations value will cause the fluid to become more viscouss.

 

Vel Iterations - Number of velocity iterations the solver should perform. Increasing the velocity iterations value will result in less splash and more regular flow.

 

Delete Rogue Liquid – The PhysX PBD liquid solver can occasionally produce "rogue" liquid particles that shoot out of the liquid at very high velocities. While these particles may not be significant during the look-dev phase, you might want to remove them for the final simulation by enabling this option. Be aware that this filtering impacts the simulation time, so use it only when necessary. By deleting particles that are far away from the main water body you will conserve a lot of time and memory during the ISurf particle meshing.

 

 

Liquid

Max Liquid Parts – Define the maximum number of liquid particles.

 

Particle Radius – A smaller radius will result in a more detailed simulation but will require more GPU memory.

 

Max Velocity – Due to complex interactions, the PhysX system can sometimes produce liquid particles with velocities exceeding physical limits. By setting this value, you can define the maximum velocity for all liquid particles, resulting in a more stable simulation..

 

Note: The amount of GPU memory that PhysX allocates for liquid particles is directly linked to the Max Liquid Parts value. To conserve GPU memory, set this value as close as possible to the actual number of liquid particles in the system. If the GPU memory required for liquid particles exceeds the available memory, PhysX will resort to using CPU memory, which will drastically reduce simulation performance. We recommend using Windows Task Manager to find the optimal values for your system.

 

 

Foam

Create Foam – Enable this option to allow foam to be generated.

 

 

Note: Due to the limited GPU memory compared to CPU, PhysX does not store foam or bubble velocity information. NodeWorks can estimate foam velocity, but calculating the velocity of bubbles rising in still water is currently not possible.

 

 

Particle Group – Define particle group to associate foam with.

 

Note: Foam particles and NodeWorks particles cannot be mixed and they have strictly separated flows. Foam particle group allow artist to use particle group display.

 

Max Foam Parts – Define the maximum number of foam particles.

 

Note: The amount of GPU memory that PhysX allocates for foam particles is directly linked to the Max Foam Parts value. To conserve GPU memory, set this value as close as possible to the actual number of foam particles in the system. If the GPU memory required for foam particles exceeds the available memory, PhysX will resort to using CPU memory, which will drastically reduce simulation performance. We recommend using Windows Task Manager to find the optimal values for your system.

 

Life Span – Foam particles will have a user-defined lifespan, after which they will be removed from the scene. The lifespan is measured in frames, so a higher value means the foam will persist longer.

 

PBD Liquid Sim – Foam Life Span variations

 

 

Use Foam Decay – Enable the algorithm to age foam in low-density regions much faster than in high-density regions.

 

Decay Threshold – Foam particles in regions with fewer particles per unit volume than this specified value will age faster.

 

PBD Liquid Sim – Foam Decay Threshold variations

 

Decay Strength – Decay multiplier for foam particles with densities below threshold.

 

PBD Liquid Sim – Foam Decay Strength variations

 

Threshold – PhysX can create foam based on various conditions within the liquid. This threshold controls the trigger level for kinetic energy, pressure and divergence. Increasing the threshold will result in less foam, as fewer liquid particles will meet the conditions.

 

PBD Liquid Sim – Foam Threshold variations

 

 

Kinetic Energy Weight – Controls foam production based on the kinetic energy of liquid particles, which is directly related to velocities in the scene. For slow-moving liquids or slow rigid bodies colliding with water, a lower threshold value is needed to emit foam. For fast-moving sources or objects, increase this value to limit the amount of foam created.

 

Pressure Weight – Controls the foam production based on the liquid particles pressure. Lower values will generate more foam.

 

Divergence Weight – Controls the foam production based on the liquid particles divergence field. Lower values will generate more foam.

 

Bubble Buoyancy – Controls how fast bubbles rise.

 

PBD Liquid Sim – Bubble Buoyancy variations

 

 

Bubble Drag – Determines the bubble motion drag when moving through the liquid.

 

Spray Air Drag – Motion drag of spray particles.

 

Collision Decay – Adjusting this parameter allows foam particles in contact with geometry to age faster than other foam particles.

 

Use Accurate Velocity –Enabling this option allows the PBD solver to use more accurate velocity estimation for foam particles.

 

Render Radius – Foam render radius – valid only when rendering with Arnold renderer. Radius at render time can be scaled through the Arnold Points settings.

 

MtlID – Foam Material ID.

 

 

Kill Planes

Main Kill Plane Z – This is the primary kill plane, responsible for deleting all particles below it. It's crucial to avoid having particles scattered throughout the scene to prevent potential issues. Therefore, this main kill plane cannot be disabled; it acts as a safety measure to remove particles that are not visually significant for the simulation.

 

Enable – Enable or disable all kill plane objects at once.

 

Kill Planes – Kill Planes are helper objects found under Helpers -> FumeFX -> Kill Plane, but users can also create and add them using the Create Kill Plane button.

 

Note: It is important that you kill all particles outside of the main water body that are not important for the simulation. If particles are scattered over a wide area there ISurf can easily occupy all your computer memory that could lead to a crash.

 

 

 

Forces

Enable – Enable or disable all force objects at once.

 

Forces – Add forces such as FumeFX Wind, Vortex, etc.

 

Forces Scale – Scale all forces at once.