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Merge dynamics node

Merges multiple streams of objects or data into a single stream.

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The Merge DOP takes any number of separate streams of objects or data and merges them into a single stream. Data and objects cannot be merged into a single stream. All inputs must be object streams, or all inputs must be data.

Merging objects does not imply any relationship between those objects. However, for convenience, the Affector Relationship parameter can be turned on to create affector relationships between the different streams of objects. The same functionality can be achieved with Group and Affector DOPs, but many more nodes would be required. Objects with the Intangible Value set will not have a relationship created by a merge node.

When merging data, any connection to this node’s output will be treated as if every input of this node is connected to it. This is useful when dealing with digital assets which provides only a single data input but to which you may wish to attach several pieces of data.

Similarly, this node can be used to allow a digital asset to output several pieces of data through a single data output. This node also provides a convenient visual method of grouping several pieces of data into a single stream for easier wiring.

Note

Bypassing this node disables the relationship calculations and only processes the first input.

Parameters

Activation

When this parameter value is zero no relationships will be added. When it is one, the Affector Relationship will control the addition of relationships. In any case, the objects are merged into a single stream.

Affector Relationship

If this node is merging streams of simulation objects, this parameter sets up affector relationships between the objects.

No Change

No new affector relationships are created between the input objects.

Left Inputs Affect Right Inputs

Given a series of inputs 1, 2, 3, and so on, the objects connected to input 1 become affectors for the objects on inputs 2, 3, and so on. The objects at input 2 become affectors of the objects at input 3 and beyond. Using this option will cause the input objects to be solved in the order in which they are connected to this node.

Mutual

All objects on all input streams become mutual affectors.

Relationship

When merging streams of objects, this determines what sort of relationship should be created between the streams. Useful choices are:

None

No affector relationship is created - the same as setting No Change in the Affector Relationship field.

Constraint

Used internally to define two objects that have a constraint between them.

Pump

Affected objects will set their local velocities to match the velocity of the source object. Applies to fluid objects.

Sink

Affected objects will delete their volume where it contacts the affectors. Applies to fluid objects.

Group

Used internally to make objects part of the same group.

Collide

Affected objects will respond to collisions from affector objects.

Target

A place holder affector for user defined effects. Used by the Gas Target Forces.

Source

Affected objects will use the affector objects as sources for operations such as creating liquid or smoke density.

Empty

Enforces a particular solve order - affected objects will be solved after affector objects - but no other intrinsic meaning.

This is useful when SOP Solvers refer to other objects creating a dependency that isn’t visible to the DOP Engine.

Inputs

All

All the objects or data connected to the inputs of this node are fed out through the single output.

Outputs

First

All the objects or data connected to the inputs of this node are fed out through the single output.

Locals

ST

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

SF

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).

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.

SFPS

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

SNOBJ

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 like object_$SNOBJ.

NOBJ

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).

OBJ

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).

OBJID

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).

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

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 $ST == $OBJCT should always be used. This value will be zero if the node does not process objects sequentially (such as the Group DOP).

OBJCF

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).

OBJNAME

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", specifying strcmp($OBJNAME, "myobject") == 0 in the activation field of a DOP will cause that DOP to operate only on those 20 objects. This value will be the empty string if the node does not process objects sequentially (such as the Group DOP).

DOPNET

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.

Note

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.

Examples

The following examples include this node.

CountImpacts Example for Count channel node

DynamicLights Example for Dynamics channel node

DynamicPops Example for Dynamics channel node

ExtractTransforms Example for Dynamics channel node

HoldLight Example for Hold channel node

Lookup Example for Lookup channel node

AnimatedActiveState Example for Active Value dynamics node

AutoFreezeRBD Example for Active Value dynamics node

SimpleAffector Example for Affector dynamics node

ClipLayerTrigger Example for Agent Clip Layer dynamics node

LookAt Example for Anchor: Align Axis dynamics node

ApplyRelationship Example for Apply Relationship dynamics node

BridgeCollapse Example for Apply Relationship dynamics node

ConstrainedTeapots Example for Apply Relationship dynamics node

MutualConstraints Example for Apply Relationship dynamics node

SimpleBlend Example for Blend Solver dynamics node

BuoyancyForce Example for Buoyancy Force dynamics node

BlanketBall Example for Cloth Object dynamics node

ClothAttachedDynamic Example for Cloth Object dynamics node

ClothFriction Example for Cloth Object dynamics node

ClothUv Example for Cloth Object dynamics node

DragCloth Example for Cloth Object dynamics node

MultipleSphereClothCollisions Example for Cloth Object dynamics node

PanelledClothRuffles Example for Cloth Object dynamics node

AnchorPins Example for Constraint Network dynamics node

AngularMotorDenting Example for Constraint Network dynamics node

BreakingSprings Example for Constraint Network dynamics node

Chains Example for Constraint Network dynamics node

ControlledGlueBreaking Example for Constraint Network dynamics node

GlueConstraintNetwork Example for Constraint Network dynamics node

Hinges Example for Constraint Network dynamics node

PointAnchors Example for Constraint Network dynamics node

SpringToGlue Example for Constraint Network dynamics node

AutoFracturing Example for Copy Objects dynamics node

SimpleCopy Example for Copy Objects dynamics node

CrowdHeightField Example for Crowd Solver dynamics node

FootLocking Example for Crowd Solver dynamics node

PartialRagdolls Example for Crowd Solver dynamics node

PinnedRagdolls Example for Crowd Solver dynamics node

Formation Crowd Example Example for Crowd Solver dynamics node

Stadium Crowd Example Example for Crowd Solver dynamics node

Street Crowd Example Example for Crowd Solver dynamics node

ClipTransitionGraph Example for Crowd Transition dynamics node

FieldForceSmoke Example for Field Force dynamics node

FromRBD Example for Field Force dynamics node

fieldforce Example for Field Force dynamics node

CacheToDisk Example for File dynamics node

FEMSpheres Example for finiteelementsolver dynamics node

DensityViscosity Example for FLIP Solver dynamics node

FlipColorMix Example for FLIP Solver dynamics node

FlipColumn Example for FLIP Solver dynamics node

FlipFluidWire Example for FLIP Solver dynamics node

VariableViscosity Example for FLIP Solver dynamics node

FluidWireInteraction Example for Fluid Force dynamics node

BallInTank Example for Fluid Object dynamics node

FillGlass Example for Fluid Object dynamics node

FluidFeedback Example for Fluid Object dynamics node

PaintedGrog Example for Fluid Object dynamics node

RiverBed Example for Fluid Object dynamics node

VariableDrag Example for Fluid Object dynamics node

HotBox Example for Gas Calculate dynamics node

DiffuseSmoke Example for Gas Diffuse dynamics node

CombinedSmoke Example for Gas Embed Fluid dynamics node

EqualizeFlip Example for Gas Equalize Volume dynamics node

EqualizeLiquid Example for Gas Equalize Volume dynamics node

dopexample_gasnetfetchdata Example for Gas Net Fetch Data dynamics node

UpresRetime Example for Gas Up Res dynamics node

grass

GuidedWrinkling Example for Hybrid Object dynamics node

MagnetMetaballs Example for Magnet Force dynamics node

SimpleMagnets Example for Magnet Force dynamics node

SimpleMultiple Example for Multiple Solver dynamics node

VolumeSource Example for Particle Fluid Emitter dynamics node

Particle fluid buoyancy

FluidGlass Example for Particle Fluid Solver dynamics node

PressureExample Example for Particle Fluid Solver dynamics node

ViscoelasticExample Example for Particle Fluid Solver dynamics node

ViscousFlow Example for Particle Fluid Solver dynamics node

WorkflowExample Example for Particle Fluid Solver dynamics node

AdvectByFilaments Example for POP Advect by Filaments dynamics node

AdvectByVolume Example for POP Advect by Volumes dynamics node

ParticlesAttract Example for POP Attract dynamics node

ParticlesIntercept Example for POP Attract dynamics node

PointAttraction Example for POP Attract dynamics node

SphereAxisForce Example for POP Axis Force dynamics node

TorusAxisForce Example for POP Axis Force dynamics node

ParticleCollisions Example for POP Collision Detect dynamics node

ColorVex Example for POP Color dynamics node

CurveForce Example for POP Curve Force dynamics node

FlockInPops Example for POP Flock dynamics node

CurlForce Example for POP Force dynamics node

BaconDrop Example for POP Grains dynamics node

KeyframedGrains Example for POP Grains dynamics node

TargetSand Example for POP Grains dynamics node

VaryingGrainSize Example for POP Grains dynamics node

SwarmBall Example for POP Interact dynamics node

LookatTarget Example for POP Lookat dynamics node

DragCenter Example for POP Property dynamics node

ProximateParticles Example for POP Proximity dynamics node

CrossTheStreams Example for POP Stream dynamics node

BillowyTurbine Example for Pyro Solver dynamics node

Stack Example for RBD Auto Freeze dynamics node

RagdollExample Example for Cone Twist Constraint dynamics node

ShatterDebris Example for RBD Fractured Object dynamics node

StackedBricks Example for RBD Fractured Object dynamics node

BlendSolverWithRBDGlue

BreakingRock

ChoreographedBreakup

ChoreographedTubeBreakup

ShatterGlass

Pendulum Example for RBD Hinge Constraint dynamics node

SimpleKeyActive Example for RBD Keyframe Active dynamics node

DeformingRBD Example for RBD Object dynamics node

FrictionBalls Example for RBD Object dynamics node

RBDInitialState Example for RBD Object dynamics node

SimpleRBD Example for RBD Object dynamics node

ActivateObjects Example for RBD Packed Object dynamics node

AnimatedObjects Example for RBD Packed Object dynamics node

DeleteObjects Example for RBD Packed Object dynamics node

EmittingObjects Example for RBD Packed Object dynamics node

Chainlinks Example for RBD Pin Constraint dynamics node

Pendulum Example for RBD Pin Constraint dynamics node

popswithrbdcollision Example for RBD Point Object dynamics node

GravitySlideExample Example for Slider Constraint dynamics node

DegreesOfFreedom Example for RBD Solver dynamics node

PaddleWheel Example for RBD Solver dynamics node

Weights Example for RBD Spring Constraint dynamics node

InheritVelocity Example for RBD State dynamics node

Simple Example for RBD Visualization dynamics node

ReferenceFrameForce Example for Reference Frame Force dynamics node

RippleGrid Example for Ripple Solver dynamics node

Freeze Example for Script Solver dynamics node

ScalePieces Example for Script Solver dynamics node

SumImpacts Example for Script Solver dynamics node

2dfluid Example for Smoke Object dynamics node

DelayedSmokeHandoff Example for Smoke Object dynamics node

Open CL smoke Example for Smoke Object dynamics node

RBDtoSmokeHandoff Example for Smoke Object dynamics node

SourceVorticlesAndCollision Example for Smoke Object dynamics node

rbdsmokesource Example for Smoke Object dynamics node

VolumePreservingSolid Example for Solid Object dynamics node

DentingWithPops Example for SOP Solver dynamics node

VisualizeImpacts Example for SOP Solver dynamics node

StaticBalls Example for Static Object dynamics node

FractureExamples Example for Voronoi Fracture Solver dynamics node

SimpleVortex Example for Vortex Force dynamics node

TurbulentSmoke Example for Wind Force dynamics node

AnimatedSkin Example for Wire Glue Constraint dynamics node

CompressedSpring Example for Wire Object dynamics node

BeadCurtain Example for Wire Solver dynamics node

BendingTree Example for Wire Solver dynamics node

CurveAdvection Example for Wire Solver dynamics node

Pendulum Example for Wire Solver dynamics node

CrowdPov Example for Agent Cam object node

AgentRelationshipBasic Example for Agent Relationship geometry node

PackedFragments Example for Assemble geometry node

MountainSplash Example for Attribute Transfer geometry node

CaptureDeform Example for Cloth Deform geometry node

ConnectedBalls Example for Connectivity geometry node

LowHigh Example for Dop Import geometry node

ProxyGeometry Example for Dop Import geometry node

dopimportrecordsexample Example for DOP Import Records geometry node

ColourAdvect Example for Fluid Source geometry node

CoolLava Example for Fluid Source geometry node

FurBallWorkflow Example for Fur geometry node

glueclusterexample Example for Glue Cluster geometry node

PartitionBall Example for Partition geometry node

AlphaOmega Example for Points from Volume geometry node

PlateBreak Example for TimeShift geometry node

TransformFracturedPieces Example for Transform Pieces geometry node

Fuzzy Logic Obstacle Avoidance Example Example for Fuzzy Defuzz VOP node

RampParameter Example for Parameter VOP node

See also

Dynamics nodes