Removes fluid particles that flow inside of a specified boundary from a simulation.
Attach this node to input 3 of the Particle Fluid Solver to create a sink/drain in the fluid simulation. This sink removes fluid particles from the simulation when they flow inside of a certain boundary. Bounding boxes, bounding spheres, metaballs or arbitrary bounding objects can be used as sinks.
For the desired results, make sure that this node is connected to the third input of the Particle Fluid Solver (the second green input). The solver may behave unpredictably if it is connected to any other input.
Using Sink Particle Fluid
Select the particle fluid to apply the sink to.
Click the Sink Particle Fluid tool on the Particle Fluids tab.
You can use the handles to drag the purple bounding box around the viewport. Any particle fluid that enters the bounding box is removed.
This example shows half of a particle fluid stream entering a Sink Particle Fluid bounding box. Only the particle fluid that enters the bounding box is removed.
Specifies the type of bounding geometry used as a sink/drain.
Bounding boxes and spheres provide the most efficient method of draining particles from a simulation, while bounding objects and metaballs can be used to provide more general but less sinks.
If Bounding Type is set to “Bounding Box” or “Bounding Sphere”, this specifies the size of the bounding geometry.
If Bounding Type is set to “Bounding Box” or “Bounding Sphere”, this specifies the center of the bounding geometry.
If Bounding Type is set to “Bounding Object” or “Bounding Metaball”, this specifies the SOP containing the bounding geometry.
|Ignore Transform Object|
When this option is off, the bounding geometry specified in SOP is automatically transformed in to the object space of the bounding geometry. When it is off, the geometry is not transformed.
If Bounding Type is set to “Bounding Metaball”, this option controls the minimum metaball density at which particles will be removed from the simulation.
The metaball field is evaluated at each particle location, and particles are removed in locations where the metaball density exceeds this threshold.
This value is the simulation time for which the node is being evaluated.
This value may not be equal to the current Houdini time represented by the variable T, depending on the settings of the DOP Network Offset Time and Time Scale parameters.
This value is guaranteed to have a value of zero at the
start of a simulation, so when testing for the first timestep of a
simulation, it is best to use a test like
This value is the simulation frame (or more accurately, the simulation time step number) for which the node is being evaluated.
This value may not be equal to the current Houdini frame number represented by the variable F, depending on the settings of the DOP Network parameters. Instead, this value is equal to the simulation time (ST) divided by the simulation timestep size (TIMESTEP).
This value is the size of a simulation timestep. This value is useful to scale values that are expressed in units per second, but are applied on each timestep.
This value is the inverse of the TIMESTEP value. It is the number of timesteps per second of simulation time.
This is the number of objects in the simulation. For nodes that create objects such as the Empty Object node, this value will increase for each object that is evaluated.
A good way to guarantee unique object names is to use an expression
This value is the number of objects that will be evaluated by the current node during this timestep. This value will often be different from SNOBJ, as many nodes do not process all the objects in a simulation.
This value may return 0 if the node does not process each object sequentially (such as the Group DOP).
This value is the index of the specific object being processed by the node. This value will always run from zero to NOBJ-1 in a given timestep. This value does not identify the current object within the simulation like OBJID or OBJNAME, just the object’s position in the current order of processing.
This value is useful for generating a random number for each object, or simply splitting the objects into two or more groups to be processed in different ways. This value will be -1 if the node does not process objects sequentially (such as the Group DOP).
This is the unique object identifier for the object being processed. Every object is assigned an integer value that is unique among all objects in the simulation for all time. Even if an object is deleted, its identifier is never reused.
The object identifier can always be used to uniquely identify a given object. This makes this variable very useful in situations where each object needs to be treated differently. It can be used to produce a unique random number for each object, for example.
This value is also the best way to look up information on an object using the dopfield expression function. This value will be -1 if the node does not process objects sequentially (such as the Group DOP).
This string contains a space separated list of the unique object identifiers for every object being processed by the current node.
This string contains a space separated list of the names of every object being processed by the current node.
This value is the simulation time (see variable ST) at which the current object was created.
Therefore, to check if an object was created
on the current timestep, the expression
This value is the simulation frame (see variable SF) at which the current object was created.
This value is equivalent to using the dopsttoframe expression on the OBJCT variable. This value will be zero if the node does not process objects sequentially (such as the Group DOP).
This is a string value containing the name of the object being processed.
Object names are not guaranteed to be unique within a simulation. However, if you name your objects carefully so that they are unique, the object name can be a much easier way to identify an object than the unique object identifier, OBJID.
The object name can
also be used to treat a number of similar objects (with the same
name) as a virtual group. If there are 20 objects named “myobject”,
This is a string value containing the full path of the current DOP Network. This value is most useful in DOP subnet digital assets where you want to know the path to the DOP Network that contains the node.
Most dynamics nodes have local variables with the same names as the node’s parameters. For example, in a Position node, you could write the expression:
$tx + 0.1
...to make the object move 0.1 units along the X axis at each timestep.
|DrainExample||Load | Launch|
This is another example to demonstrate how to use Particle Fluid Sinks in a simulation. This also demonstrates how to properly combine Particle Fluid Emitters with sinks in a simulation.
|TankDrain||Load | Launch|
This simple example demonstrates how to use a sink to drain particles from a simulation. A tank full of fluid with a hole in the bottom is set up. A sink is placed beneath the tank so that particles flowing out of the tank are removed from the simulation.
Other examples that use this node
|Example for||Example name|
|FLIP Solver||FlipColorMix||Load | Launch|
|FLIP Solver||FlipFluidWire||Load | Launch|
|Particle Fluid Emitter||DrainExample||Load | Launch|