Houdini 20.0 Nodes Dynamics nodes

Hybrid Configure Object dynamics node

Attaches the appropriate data for Hybrid Objects to an object.

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Since 16.0

The Hybrid Configure Object DOP takes a simulation object and attaches the data which is needed for it to be used as a Hybrid Object.

This DOP is very similar to the Hybrid Object DOP, except it allows you to explicitly control the creation of the object using another DOP, such as the Empty Object DOP. This can be used for more advanced instancing or creating objects every 10 frames.

Parameters

Model

Stiffness Multiplier

This is a convenient multiplier for both the Shape Stiffness and the Bend Stiffness of the shell polygons. This multiplier has no units.

Damping Ratio

This unitless parameter controls how quickly the shell polygons stop deforming.

Mass Density

This is the density of mass per volume for the polygons.

Thickness

This specifies the volume per surface area for the shell polygons.

Shape Stiffness

This determines how strongly the shell polygons resist local deformation in directions tangent to the shell.

Bend Stiffness

This determines how strongly the shell polygons resist local deformation in directions normal to the shell.

Stiffness Multiplier

This is a convenient multiplier for both the Shape Stiffness and the Volume Stiffness of the solid tets. This multiplier has no units.

Damping Ratio

This unitless parameter controls how quickly the solid tets stop deforming.

Mass Density

This is the density of mass per volume for the solid tets.

Material Model

Choose the model that determines how the material resists deformation.

Shape Stiffness

This determines how strongly the solid tets resist local changes in shape.

Volume Stiffness

This determines how strongly the solid tets resist local changes in volume.

Deformation

Initial

Initial State

The path to the SOP node with the initial connectivity, position and velocity.

Rest

Rest Shape

The path to the SOP node that defines the rest shape.

Target

Target Deformation

The path to the SOP node with target deformation.

Target Strength

Strength density of the distributed soft-constraint force field that tries to match the target position.

Target Damping

Damping density of the distributed soft-constraint force field that tries to match the target velocity.

Attributes

Create Quality Attributes

This creates a primitive attribute 'quality' on the simulated geometry. The worst quality is 0, the best quality is 1. The better the quality of the primitives, the better the performance and stability of the solve will be.

Create Energy Attributes

This toggle allow the object to generate attributes that indicate the density of kinetic energy and potential energy. In addition, an attribute that indicates the density of the rate of energy loss is generated.

Create Force Attributes

This toggle allows force attributes to be generated.

Create Collision Attributes

Create Fracture Attributes

Creation

Locals

ST

The simulation time for which the node is being evaluated.

Depending on the settings of the DOP Network Offset Time and Scale Time parameters, this value may not be equal to the current Houdini time represented by the variable T.

ST 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 $ST == 0, rather than $T == 0 or $FF == 1.

SF

The simulation frame (or more accurately, the simulation time step number) for which the node is being evaluated.

Depending on the settings of the DOP Network parameters, this value may not be equal to the current Houdini frame number represented by the variable F. Instead, it is equal to the simulation time (ST) divided by the simulation timestep size (TIMESTEP).

TIMESTEP

The size of a simulation timestep. This value is useful for scaling values that are expressed in units per second, but are applied on each timestep.

SFPS

The inverse of the TIMESTEP value. It is the number of timesteps per second of simulation time.

SNOBJ

The number of objects in the simulation. For nodes that create objects such as the Empty Object DOP, SNOBJ increases for each object that is evaluated.

A good way to guarantee unique object names is to use an expression like object_$SNOBJ.

NOBJ

The number of objects that are evaluated by the current node during this timestep. This value is often different from SNOBJ, as many nodes do not process all the objects in a simulation.

NOBJ may return 0 if the node does not process each object sequentially (such as the Group DOP).

OBJ

The index of the specific object being processed by the node. This value always runs from zero to NOBJ-1 in a given timestep. It does not identify the current object within the simulation like OBJID or OBJNAME; it only identifies 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 is -1 if the node does not process objects sequentially (such as the Group DOP).

OBJID

The unique 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. This is very useful in situations where each object needs to be treated differently, for example, to produce a unique random number for each object.

This value is also the best way to look up information on an object using the dopfield expression function.

OBJID is -1 if the node does not process objects sequentially (such as the Group DOP).

ALLOBJIDS

This string contains a space-separated list of the unique object identifiers for every object being processed by the current node.

ALLOBJNAMES

This string contains a space-separated list of the names of every object being processed by the current node.

OBJCT

The simulation time (see variable ST) at which the current object was created.

To check if an object was created on the current timestep, the expression $ST == $OBJCT should always be used.

This value is zero if the node does not process objects sequentially (such as the Group DOP).

OBJCF

The simulation frame (see variable SF) at which the current object was created. It is equivalent to using the dopsttoframe expression on the OBJCT variable.

This value is zero if the node does not process objects sequentially (such as the Group DOP).

OBJNAME

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”, specifying strcmp($OBJNAME, "myobject") == 0 in the activation field of a DOP will cause that DOP to operate on only those 20 objects.

This value is the empty string if the node does not process objects sequentially (such as the Group DOP).

DOPNET

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.

Note

Most dynamics nodes have local variables with the same names as the node’s parameters. For example, in a Position DOP, you could write the expression:

$tx + 0.1

…to make the object move 0.1 units along the X axis at each timestep.

See also

Dynamics nodes