--- title: "Liquids" url: "https://help.maxon.net/c4d/en-us/Content/html/OPBDSCENE-PBDSCENE_LIQUIDS_GROUP.html" section_path: "Simulate Menu > The Simulation System > Simulation Scene > Liquids" element_id: "OPBDSCENE" group_id: "PBDSCENE_LIQUIDS_GROUP" description: "Here you will find preferences that can be used to specifically set the evaluation of the particles involved in a fluid simulation. These are therefore …" --- ## Liquids Here you will find preferences that can be used to specifically set the evaluation of the particles involved in a fluid simulation. These are therefore mainly the particles that were generated at a [Liquid Fill Emitter](https://help.maxon.net/c4d/en-us/Content/html/OFPLIQUIDFILLEMITTER.html.md), a Liquid Flow Emitter, a Liquid FX Emitter or basic particles that were converted to liquid particles by a [Liquify Modifier](https://help.maxon.net/c4d/en-us/Content/html/OFPLIQUIFY.html.md).\ Also keep in mind that the *Particle* settings from the [Simulation Settings](https://help.maxon.net/c4d/en-us/Content/html/OPBDSCENE-PBDSCENE_GROUP_XPBDPROPERTIES.html.md) also affect the liquid particles. This can be used, for example, to control the general accuracy of the simulation and collision detection or the intensity of gravity. ### Default Radius Parameter ID: `PBDSCENE_LIQUIDS_RADIUS` · Range: [0..+∞m] This radius defines the size of a single liquid particle. Smaller radii generally lead to more definition within the simulation, as more more particles can be created in the same volume. However, in order to obtain the same volume of liquid, more particles must be emitted. In general, the computational effort for the simulation and its memory requirements increase as the radius of the liquid particles decreases. Therefore, try to work with a larger radius at first and only reduce it further if additional details are required in the liquid.\ Please also note that the individual radius of the emitted particles can also be taken over by the liquid particles. To do this, deactivate the option for **Use Default Radius** on the *Liquify* modifier. This means that the regular **Radius** property is also adopted for the liquid particles for particles created using standard emitters, provided that they are converted to a liquid using a *Liquify Modifier*. ### Neighbors Passes Parameter ID: `PBDSCENE_LIQUIDS_NEIGHBORS_PASSES` · Range: [0..1000] This value controls the number of calculation loops during a simulation frame in order to determine the forces between the particles evaluated for the fluid calculation. These include, for example, the simulated *Surface Tension* and the *Viscosity* of the liquid. In general, more calculation steps always lead to a higher accuracy of the simulation, but are also accompanied by a corresponding increase in simulation times for each frame. ### Extra Iterations Parameter ID: `PBDSCENE_LIQUIDS_EXTRA_ITERATIONS` · Range: [0..1000] This value is also used to define a number of calculation steps for the liquid particles, but this time for the simulation phase, after the force relationships between neighboring particles and any collider objects have already been determined. This means that the final state of the individual particles can be inspected again and corrected if necessary.\ As this is only a correction factor, small values are often sufficient. It is generally recommended to run at least one additional iteration here. ### Viscosity Iterations Parameter ID: `PBDSCENE_LIQUIDS_VISCOSITY_ITERATIONS` · Range: [0..1000] **Viscosity** is used to define the resistance of a liquid to a flow movement. A low **Viscosity** value therefore leads to the simulation of water, for example, whereas a higher value enables the simulation of honey, for example.\ Use this value to specify the number of calculation runs that are only used to simulate the **Viscosity** on the liquid particles. ### Surface Tension Iterations Parameter ID: `PBDSCENE_LIQUIDS_SURFACETENSION_ITERATIONS` · Range: [0..1000] The Surface Tension of a liquid determines how strongly neighboring particles attract each other or how strongly they try to stay in contact, even if neighboring particles want to move in different directions. In relation to water, Surface Tension leads, for example, to the classic formation of droplets and the clumping of particles that come closer together. If the Surface Tension is very high, the liquid can separate into individual groups, whereas a lower Surface Tension can lead to a more homogeneous distribution of the liquid particles.\ Use this value to specify the number of calculation runs that are only used to simulate the **Surface Tension** on the liquid particles. ### Acceleration Clamp Override Parameter ID: `PBDSCENE_LIQUIDS_ACCELERATIONCLAMP_OVERRIDE` In the [Simulation Settings](https://help.maxon.net/c4d/en-us/Content/html/OPBDSCENE-PBDSCENE_GROUP_XPBDPROPERTIES.html.md), you will also find an option to limit the acceleration values within the simulation. By activating this **Override** option, an independent Clamp value can also be specified specifically for the liquid simulation. This can help to reduce excessive fluid movements, but can also lead to a slowdown of the entire fluid simulation if the values are too small. Therefore, only use this option if other options, such as increasing the **Damping** or reducing the acting forces, do not lead to the desired result. ### Acceleration Clamp Size Parameter ID: `PBDSCENE_LIQUIDS_ACCELERATIONCLAMP_ABSOLUTE_SIZE` · Range: [0..+∞m] If the option for **Acceleration Clamp Override** has been activated, a maximum value can be specified here for a still permissible acceleration within the fluid simulation. If higher acceleration values are determined within the simulation, these are automatically reduced to this maximum value. This can be used to avoid extreme speeds, e.g. under the influence of external forces. 2027 Spray, Foam and Bubbles ### Spray Parameter ID: `PBDSCENE_SPRAYFOAMBUBBLES_GROUP_GROUP_SPRAY` ### Foam Parameter ID: `PBDSCENE_SPRAYFOAMBUBBLES_GROUP_GROUP_FOAM` ### Bubbles Parameter ID: `PBDSCENE_SPRAYFOAMBUBBLES_GROUP_GROUP_BUBBLES` Here you can assign particle groups in which the liquid particles for *Spray*,*Foam*, and *Bubbles* are to be managed. Please note that these particles naturally switch between groups automatically. For example, *Bubbles* turn into *Foam* when they come into contact with the liquid’s surface. *Foam* that moves too far away from the liquid turns into *Spray*, and *Spray* that touches the liquid or penetrates it turns back into *Foam* or *Bubbles*. Classify ### Bubbles Neighbors Threshold Parameter ID: `PBDSCENE_SPRAYFOAMBUBBLES_CLASSIFY_NEIGHBORS_THRESHOLD_BUBBLES` · Range: [0..1000] Minimum nearby particle count for *Bubble* particles emission activation. ### Spray Neighbors Threshold Parameter ID: `PBDSCENE_SPRAYFOAMBUBBLES_CLASSIFY_NEIGHBORS_THRESHOLD_SPRAY` · Range: [0..1000] Minimum nearby particle count for *Spray* particle emission activation.