Houdini 20.5 Expression functions

ch expression function

Returns the value of a parameter.

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HOM equivalent

hou.OpNode.evalParm()

hou.Parm

hou.ParmTuple.eval()

hou.ch()

hou.evalParm()

hou.evalParmTuple()

hou.nodeBySessionId()

hou.node()

hou.nodes()

hou.parmTuple()

hou.parm()

Overview

The ch family of functions gets the value of a parameter. This lets you make the values of certain parameters automatically identical to or relative to the value of other parameters.

For example, if you have two Geometry object nodes named geo1 and geo2, you can make geo2 always be 2 units higher than geo by setting geo2's Translate Y parameter to:

ch("../geo1/ty") + 2

Now when you move geo1, geo2's Y position will always be 2 units higher.

Channel references let you create custom spare parameters and digital asset interfaces and have them control other nodes, by using channel references to have the nodes inside the subnetwork/asset reference the “interface” parameters at the higher level.

Path argument

The first argument to the channel functions is a string path to the parameter whose value you want to get.

For parameters on the same node, you can just use the parameter’s internal name. For example, in an object, you could make the object’s X position always match the Y position by setting the Translate Y to the expression:

ch("ty")

Tip

You can find the internal name of a parameter in the tooltip when you hover the mouse over the parameter in the parameter editor.

To get a parameter on a different node, you need to make a path to the parameter, similar to UNIX directory paths.

For example, to reference the ty parameter of a node named geo2 in the same network:

ch("../geo2/ty")

To reference the tx parameter of the parent network node:

ch("../tx")

Getting numbers

ch("path")

Returns the floating point value of the given parameter.

For example, to get the Origin X of the font1 node:

ch("../font1/tx")

chf("path", frame_num)

Returns the floating point value of the given parameter, as computed at the given frame number.

Getting a value from a future time requires cooking some or all of the scene up to that time, so this function is potentially expensive.

For example, to get the Origin X of the font1 node from ten frames previous:

chf("../font1/text", $F - 10)

cht("path", seconds)

Returns the floating point value of the given parameter, as computed at the given time (in seconds).

Getting a value from a future time requires cooking some or all of the scene up to that time, so this function is potentially expensive.

For example, to get the Origin X of the font1 node from 2 seconds previous:

chf("../font1/text", $T - 2)

Getting strings

chs("path")

Returns the string value of the given parameter.

For example, to get the Text of the font1 node:

chs("../font1/text")

chsraw("path")

Returns the “raw” string value of the given parameter, without expanding quotes or variable names. For example, if the parameter contains an expression $F - 10, you will get the string "$F - 10" (instead of the computed value of the current frame minus ten).

Getting a node path

See chsop.

Getting ramp values

See chramp, chrampf, and chrampt.

Tips

  • You can automatically create channel-references using the “Copy” and “Paste reference” commands on the parameter right-click menu.

  • See linking parameter values for more information.

See also

Expression functions

  • abs

    Returns the absolute value of the argument.

  • abspath

    Returns the full path of a file.

  • acos

    Returns the arc-cosine of the argument.

  • angvel

    Returns the angular velocity required to rotate an object from one orientation to another in a certain period of time.

  • arclen

    Returns the arc length of a curve between two U positions.

  • arclenD

    Returns the arc length of a curve between two U positions and number of divisions.

  • arg

    Returns an argument from a list of HScript-style arguments.

  • argc

    Returns the number of arguments in an HScript-style list of arguments.

  • asin

    Returns the arc-sine of the argument.

  • atan

    Returns the arc-tangent of the argument.

  • atan2

    Returns the arc-tangent of y/x.

  • atof

    Converts a string to a float.

  • attriblist

    Returns a space-separated list of attribute names.

  • bbox

    Returns bounding box information for a surface node.

  • bezier

    Channel segment function: Bezier interpoloation spline

  • bitand

    Combines two numbers with bitwise-and.

  • bitor

    Combines two numbers with bitwise-or.

  • bitset

    Sets or clears a bit in a number.

  • bittest

    Returns if a given bit is set.

  • bitxor

    Combines two numbers with bitwise-xor.

  • boneangle

    Returns the angle at the joint between two bone objects.

  • ceil

    Returns the smallest integer not less than the value passed in.

  • centroid

    Returns centroid information for a surface node.

  • ch

    Returns the value of a parameter.

  • chexist

    Returns 1 if the specified channel exists, 0 if it doesn’t.

  • chexpr

    Evaluates a channel with a new segment expression.

  • chexprf

    Evaluates a channel with a new segment expression at a given frame.

  • chexprt

    Evaluates a channel with a new segment expression at a given time.

  • chf

    Evaluates a parameter at a given frame.

  • chgroup

    return a string containing all of the channels contained in a group.

  • chop

    Evaluates a channel within a CHOP at the current time.

  • chopcf

    Evaluates a channel within a CHOP at a given time.

  • chopci

    Evaluates a channel within a CHOP at a specified sample point.

  • chopct

    Evaluates a channel within a CHOP at a specified time.

  • chope

    Returns the end index of the channels in a CHOP.

  • chopf

    Evaluates a channel within a CHOP with at a given frame.

  • chopi

    Evaluates a channel within a CHOP at a given sample point.

  • chopl

    Returns the length of the channels in a CHOP, in samples.

  • chopn

    Returns the number of data channels within a CHOP.

  • chopnames

    Returns the names of all the data channels within a CHOP.

  • chopr

    Returns the sample rate of a CHOP.

  • chops

    Returns the start index of a CHOP.

  • chopstr

    Returns the string value of a channel within a CHOP at the current time.

  • chopt

    Returns the value of a channel within a CHOP at a specified time.

  • chramp

    Returns the value of a ramp parameter at a specific position.

  • chrampf

    Returns the value of a ramp parameter at a specific position and frame.

  • chrampt

    Returns the value of a ramp parameter at a specific position and time.

  • chs

    Evaluates the string value of a parameter at the current time.

  • chsop

    Evaluates the parameter at the current time as a node path string.

  • chsoplist

    Evaluates the parameter at the current time as a node path list string.

  • chsraw

    Returns the raw (unexpanded) expression value of a parameter as a string.

  • cht

    Returns the value of a parameter at a specified time.

  • clamp

    Returns a value clamped between a minimum and maximum.

  • clamptosphere

    Clamps a vector to always end between a minimum and maximum sphere.

  • constant

    Channel segment function: constant value.

  • contextoption

    Returns the value of context option as a floating point value.

  • contextoptions

    Returns a cook context option as a string value.

  • cophasmeta

    Tests if metadata exists on a compositing node.

  • cophasplane

    Tests if a plane exists on a compositing node.

  • copmeta

    Returns numeric metadata from a compositing node.

  • copmeta

    Returns string metadata from a compositing node.

  • cos

    Returns the cosine of the argument.

  • cosh

    Returns the hyperbolic cosine of the argument.

  • cross

    Computes the cross-product of two vectors.

  • cubic

    Channel segment function: cubic spline.

  • cucwc

    Deprecated: current working container for custom panels.

  • cudatatype

    Deprecated: data type of a gadget, for custom panels.

  • cumenuadd

    Deprecated: adds a menu entry on a custom panel.

  • cuquery

    Deprecated: returns a value from a custom panel.

  • curvature

    Returns the curvature of the surface at the given UV coordinates.

  • cutype

    Deprecated: Returns the type of a gadget on a custom panel.

  • cycle

    Channel segment function: repeats animation from previous frames.

  • cycleoffset

    Channel segment function: repeats the animation between frames f1 and f2, accumulating the value.

  • cycleoffsett

    Channel segment function: repeats the animation between times t1 and t2, accumulating the value.

  • cyclet

    Channel segment function: repeats animation from previous frames.

  • decode

    Decodes a variable name that was previously encoded.

  • decodeattrib

    Decodes a geometry attribute name that was previously encoded.

  • decodeparm

    Decodes a node parameter name that was previously encoded.

  • deg

    Converts from radians to degrees.

  • degree

    Returns the degree a specified face or hull.

  • detail

    Returns the value of a detail attribute.

  • detailattriblist

    Returns a space-separated list of detail attribute names.

  • detailattribsize

    Returns the number of components in a detail attribute.

  • detailattribtype

    Returns the type of a detail attribute.

  • details

    Returns the string value of a detail attribute.

  • detailsmap

    Returns a string from a list of strings in a detail attribute.

  • detailsnummap

    Returns the number of unique strings bound to a detail attribute.

  • detailvals

    Returns components of a string array attribute.

  • determinant

    Returns the determinant of a matrix.

  • dihedral

    Computes the dihedral matrix between vectors v0 and v1.

  • distance

    Returns the distance between two 3D points.

  • dopallfields

    Returns a space separated list of all the field names that can be passed to the dopfield function.

  • dopcontextgeo

    Returns the full path of the node connected to a dopnetwork.

  • dopcountslices

    Returns the number of records of a given type in a piece of dynamics data.

  • dopfield

    Returns the value of a field as a float.

  • dopfieldname

    Returns the name of a DOP field.

  • dopfields

    Returns the value of a DOP field as a string.

  • dopfieldtype

    Returns the type of a DOP field.

  • dopframe

    Returns the current frame of the simulation.

  • dopframetost

    Returns the simulation time equivalent of a simulation frame.

  • dopgrouphasobject

    Returns 1 if a specified DOP group contains a specified object.

  • dopgroupismutual

    Returns 1 if a specified DOP group is mutually affecting.

  • dopgrouplist

    returns a string containing a list of all object groups for the current time in a specified DOP Network.

  • dophasfield

    Returns 1 if a specified DOP field exists.

  • dophassubdata

    Returns 1 if a dynamics object has the specified subdata.

  • dopnodeobjs

    Returns the list of objects processed by a DOP in the latest timestep.

  • dopnumfields

    Returns the number of fields in a DOP record type.

  • dopnumobjects

    returns the number of objects in a simulation.

  • dopnumrecords

    Returns the number of records of a given type in a piece of dynamics data.

  • dopnumrecordtypes

    Returns the number of types of record in a piece of dynamics data.

  • dopnumsubdata

    Returns the number of subdata items attached to an object or data.

  • dopobjectlist

    Returns all objects matching the an object specification.

  • dopobjectsareaffectors

    Tests whether a set of objects has an affector relationship with another object.

  • dopobjscreatedby

    Returns the list of objects created by a particular DOP node.

  • dopoption

    Returns the value of a DOP field as a float.

  • dopoptions

    Returns the value of a DOP field as a string.

  • doprecordtypename

    Returns the name of a record in DOPs data given its index.

  • dopsolvedopnet

    Script solver support function.

  • dopsolvenewobject

    Script solver support function.

  • dopsolvenumnewobjects

    Script solver support function.

  • dopsolvenumobjects

    Script solver support function.

  • dopsolveobject

    Script solver support function.

  • dopsolvetimestep

    Script solver support function.

  • dopsttoframe

    returns the simulation frame of a given simulation time.

  • dopsttot

    Returns the global time of a given simulation time.

  • dopsubdataname

    Returns the name of a subdata of a given DOP object.

  • doptime

    Returns the current time of a simulation.

  • doptransform

    Returns a transformation matrix associated with a piece of data.

  • dopttost

    Returns the simulation time equivalent to a given global time.

  • dopvelatpos

    Returns the velocity that a point at a location in simulation space would have if it were attached to a DOP object.

  • dot

    Computes the dot product of two vectors.

  • ease

    Channel segment function: ease-in and -out.

  • easein

    Channel segment function: ease-in.

  • easeinp

    Channel segment function: ease-in with configurable acceleration.

  • easeout

    Channel segment function: ease-out

  • easeoutp

    Channel segment function: ease-out with configurable acceleration.

  • easep

    Channel segment function: ease-in and -out with configurable acceleration.

  • edgegrouplist

    Returns the list of edge groups in a surface node.

  • edgegroupmask

    Returns the list of edge groups matching a pattern in a surface node.

  • efit

    Fits a value from one range to another.

  • encode

    Encodes any string into a valid variable name.

  • encodeattrib

    Encodes any string into a valid geometry attribute name.

  • encodeparm

    Encodes any string into a valid node parameter name.

  • eval

    Evaulates a string as an expression returning a float.

  • evals

    Evaulates a string as an expression returning a string.

  • execute

    Runs a string as an HScript command and returns the command’s output.

  • executeb

    Runs a string as an HScript command and returns the command and error output.

  • executee

    Runs a string as an HScript command and returns any error output.

  • exp

    Returns the logarithmic exponentiation of the argument.

  • explodematrix

    Explodes a 3×3 or 4×4 matrix into the euler rotations required to rebuild it.

  • explodematrixp

    Explodes a 3×3 or 4×4 matrix into the euler rotations required to rebuild it.

  • explodematrixpr

    Explodes a 3×3 or 4×4 matrix into the euler rotations required to rebuild it.

  • findfile

    Searches the Houdini path for a file.

  • findfiles

    Searches the Houdini path for a file or directory.

  • fit

    Fits a value from one range to another.

  • fit01

    Fits a value to the 0-1 range.

  • fit10

    Fits a number in the 0-1 range.

  • fit11

    Fits a number to the -1 to 1 range.

  • floor

    Returns the largest integer not greater than a number.

  • fpadzero

    Returns a string padding a number to a given length with zeros.

  • frac

    Returns the fractional part of a floating-point number.

  • ftoa

    Converts a number to a string.

  • ftrim

    Converts a number to a string, with rounding.

  • groupbyval

    Returns a string describing the set of elements with a given value for an integer attribute.

  • groupbyvals

    Returns a string describing the set of elements with a given value for a string attribute.

  • hascontextoption

    Returns a non-zero value if the specified context option exists.

  • hasdetailattrib

    Returns 1 if a specified detail attribute exists.

  • haspdgattrib

    Returns 1 if the active PDG work item has the specified attribute.

  • haspoint

    Returns 1 if a specified point is in a specified group.

  • haspointattrib

    Returns 1 if a specified point attribute exists.

  • hasprim

    Returns 1 if a specified primitive is in a specified group.

  • hasprimattrib

    Returns 1 if a specified primitive attribute exists.

  • hasvertexattrib

    Returns 1 if a specified vertex attribute exists.

  • hextoint

    Converts a hexadecimal argument string into an integer.

  • hsv

    Converts RGB values to HSV components.

  • ic

    Evaluates a CHOP’s input channel at a specific index.

  • ice

    Returns the end index of a CHOP’s input.

  • icl

    Returns the length of a CHOP’s input, in samples.

  • icmax

    Evaluates a CHOP’s input channel’s maximum value.

  • icmin

    Evaluates a CHOP’s input channel’s minimum value.

  • icn

    Returns the number of channels in a CHOP’s input.

  • icr

    Returns the sample rate of a CHOP’s input.

  • ics

    Returns the start index of a CHOP’s input.

  • identity

    Creates an identity matrix.

  • if

    Returns the value of the second or third argument depending on the truth of the first argument.

  • ifs

    Returns the string value of the second or third argument depending on the truth of the first argument.

  • index

    Finds the first occurrence of a pattern in a string.

  • instancepoint

    Returns the point number currently being instanced onto.

  • int

    Converts a number to an integer by truncating any fractional part.

  • inttohex

    Converts a number into a hexadecimal string.

  • invert

    Inverts a matrix.

  • iprquery

    Queries numeric (floating point) data from an interactive render pane.

  • iprquerys

    Queries textual (string) data from an interactive render pane.

  • isclosed

    Returns 1 if a primitive is closed.

  • iscollided

    Returns 1 if a specified point has collided with something.

  • ishvariable

    Returns 1 if a specified Houdini environment variable exists.

  • ispdgeval

    Returns 1 if the parameter is being evaluated as part of a PDG cook, else 0

  • isspline

    Returns 1 if a specified primitive is a NURBs or Bezier curve or surface.

  • isstuck

    Returns 1 if a specified point is a stuck particle.

  • isvariable

    Returns 1 if a specified Houdini or system environment variable exists.

  • iswrapu

    Returns 1 if a specified primitive is wrapped in U.

  • iswrapv

    Returns 1 if a specified primitive is wrapped in V.

  • length

    Returns the length of a vector.

  • linear

    Channel segment function: linear interpolation.

  • listbyval

    Returns a list of elements with a given value for an integer attribute.

  • listbyvals

    Returns a list of elements with a given value for a string attribute.

  • lock

    Returns a value that cannot be changed.

  • log

    Returns the natural logarithm of the argument.

  • log10

    Returns the base 10 logarithm of the argument.

  • lopinputprim

    Returns the path of the USD primitive last modified by an input to a LOP node.

  • lopinputprims

    Returns the paths of the USD primitives last modified by an input to a LOP node.

  • loplastmodifiedprim

    Returns the path of the USD primitive last modified by a LOP node.

  • loplastmodifiedprims

    Returns the paths of the USD primitives last modified by a LOP node.

  • lopparentprims

    Returns the paths of the parents of the supplied list of USD primitives.

  • loprelativeprims

    Returns the paths at a particular location relative to the supplied list of USD primitives.

  • ltrim

    Trims white sapce from the front of a string.

  • match

    Channel segment function: matches the incoming and outgoing values.

  • matchin

    Channel segment function: matches the incoming slope.

  • matchout

    Channel segment function: matches the outgoing slope.

  • matrix

    Converts a string specification into a matrix.

  • matrixtoquat

    Converts a rotation matrix to a quaternion.

  • max

    Returns the larger of two values.

  • mcols

    Returns the number of columns in a matrix.

  • metaweight

    Returns the weight of a metaball at a specific location.

  • min

    Returns the smaller of two values.

  • mindist

    Finds the smallest distance between a point and a primitive.

  • mlookat

    Computes the transformation matrix of a lookat from one vector to another.

  • mlookatup

    Computes the transformation matrix of a lookat from one vector to another, with an up vector.

  • mobjlookat

    Computes the transformation matrix of a lookat from one object to another.

  • modblend

    Blends the two modular values.

  • morient

    Computes the transformation matrix to orient along specific Z and Y axes.

  • mousepane

    Returns the full name of the pane currently under the mouse pointer.

  • mousepath

    Returns the node path of the pane currently under the mouse pointer.

  • mrows

    Returns the number of rows in a matrix.

  • mzero

    Returns a matrix with all values set to 0.

  • nearpoint

    Finds the point in a geometry nearest to specific 3D coordinates.

  • noise

    Generates 3D noise.

  • normal

    Returns the components of the surface normal specific UV coordinates.

  • normalize

    Normalizes a vector.

  • npoints

    Returns the number of points in a geometry.

  • npointsgroup

    Returns the number of points in the specified group.

  • nprims

    Returns the number of primitives in a surface node.

  • nprimsgroup

    Returns the number of primitives in the specified group.

  • nuniquevals

    Returns the number of unique values for an integer or string attribute in a surface node.

  • nvertices

    Returns the number of vertices in a geometry.

  • nverticesgroup

    Returns the number of vertices in the specified group.

  • objkinoverride

    Returns the current global kinematic override setting for bone objects.

  • objlightmask

    Returns a list of lights matching an object’s light mask.

  • objlookat

    Computes the rotation vector of a lookat from one object to another.

  • objpretransform

    Returns an object’s pre-transform matrix.

  • oc

    Returns the value of a CHOP’s output at a specific sample index.

  • ocldeviceinfo

    Queries the current OpenCL device with the provided flag

  • oldrand

    Returns a pseudo-random number between 0 and 1.

  • opblist

    Returns the full paths of all operators in a bundle.

  • opcreator

    Returns the creator of this node.

  • opdigits

    Returns the numeric suffix of a node name.

  • opexist

    Returns 1 if the specified node, group, or bundle exists.

  • opflag

    Returns a list nodes with a particular flag set.

  • opfullpath

    Returns the full path of a node.

  • opfullpathfrom

    Returns the path of a node relative to another node.

  • opid

    Returns the unique ID of a node.

  • opinput

    Returns the name of the node connected to a given input.

  • opinputpath

    Returns the full path of the node connected to a given input.

  • opinputstring

    Returns the value associated with a key string on node connection.

  • opisloading

    Returns 1 if Houdini is currently loading a scene file.

  • opisquitting

    Returns 1 if Houdini is currently shutting down.

  • oplightmask

    Returns a list of lights matching an object’s light mask.

  • oplistsort

    Sorts a list of node paths based on node input/outputs order.

  • opname

    Returns the name of a node given its path.

  • opnchildren

    Returns the number of nodes inside a container node.

  • opninputs

    Returns the maximum number of connected inputs.

  • opnodigits

    Returns the alphanumeric prefix of a node name eliminating trailing digits.

  • opnoutputs

    Returns the number of nodes connected to a node’s output.

  • opoutput

    Returns the name of a node connected a given node’s output.

  • opoutputpath

    Returns the full path of a node connected a given node’s output.

  • oppinput

    Deprecated: replaced by opinput.

  • oppwd

    Returns the path of the current network.

  • oppwf

    Prints the path of the current network.

  • oprelativepath

    Returns the relative path from one node to another.

  • opselect

    Returns a list of the selected nodes.

  • opselectpath

    Returns a list of the full paths of selected nodes.

  • opselectrecurse

    Returns a recursive list of the selected nodes.

  • opselectrecursepath

    Returns a recursive list of the full paths of selected nodes.

  • opstreamname

    Computes the active stream of a node.

  • opsubpath

    Returns the full path of a node including any containing subnets.

  • optransform

    Returns the transformation matrix of an object at the current time.

  • optype

    Returns the type of a node.

  • optypeinfo

    Returns type information about a node.

  • origin

    Returns components of an object’s transforms.

  • originoffset

    Returns components of an object’s offset transforms.

  • padzero

    Returns a string padding a number to a given length with zeros.

  • param

    Deprecated: use stamp instead.

  • parmisstring

    Returns 1 if a specified parameter is a string.

  • pdgattrib

    Returns the value of a PDG work item attrib

  • pdgattriblist

    Returns a space-separated list of attribute names on the active PDG work item.

  • pdgattribs

    Returns the string value of a PDG work item attribute

  • pdgattribsize

    Returns the number of components in a PDG work item attribute.

  • pdgattribtype

    Returns the type of a PDG work item attribute.

  • pdgattribute

    Deprecated: replaced by pdgattrib.

  • pdgattributes

    Deprecated: replaced by pdgattribs.

  • pdgattribvals

    Returns the space separated list of values for a PDG work item attribute

  • pdginput

    Returns a work item input file for the specified file index and tag

  • pdginputsize

    Returns the number of input files on the active PDG work item

  • pdginputtag

    Returns the file tag for the input file at the specified index.

  • pdginputvals

    Returns a space separated string of all work item input files for the specified tag

  • pdgmappath

    Maps the given path to the local Zone

  • pdgoutput

    Returns a work item output file for the specified file index and tag

  • pdgoutputsize

    Returns the number of output files on the active PDG work item

  • pdgoutputtag

    Returns the file tag for the output file at the specified index.

  • pdgoutputvals

    Returns a space separated string of all work item output files for the specified tag

  • pic

    Returns the color of a pixel in a compositing node.

  • picni

    Returns the non-interpolated color of a pixel in a compositing node.

  • pluralize

    Converts an English noun to its plural.

  • point

    Returns the value of a point attribute.

  • pointattriblist

    Returns a space-separated list of point attribute names.

  • pointattribsize

    Returns the number of components in a point attribute.

  • pointattribtype

    Returns the type of a point attribute.

  • pointavg

    Returns the average of an attribute across all points in a geometry.

  • pointdist

    Returns the distance between a point and a primitive.

  • pointgrouplist

    Returns the list of point groups in a surface node.

  • pointgroupmask

    Returns the list of point groups matching a pattern in a surface node.

  • pointlist

    Returns a list of all points in a point group.

  • pointneighbours

    Lists points that share a minimum number of primitives with a specified point.

  • pointpattern

    Returns a list of points that match a specified pattern.

  • points

    Returns the string value of a point attribute.

  • pointsmap

    Returns a string from a list of strings in a point attribute.

  • pointsnummap

    Returns the number of unique strings bound to a point attribute.

  • pointvals

    Returns components of a string array attribute.

  • pow

    Raises a number to an exponent.

  • prim

    Returns the value of a primitive attribute.

  • primattriblist

    Returns a space-separated list of primitive attribute names.

  • primattribsize

    Returns the number of components in a primitive attribute.

  • primattribtype

    Returns the type of a primitive attribute.

  • primdist

    Returns the minimum distance and closest points between two primitives.

  • primduv

    Returns the partial derivatives of a primitive attribute.

  • primgrouplist

    Returns the list of primitive groups in a surface node.

  • primgroupmask

    Returns the list of groups matching a pattern in a surface node.

  • primlist

    Returns a list of all primitives in a surface node.

  • primneighbours

    Lists primitives that share a minimum number of points with a specified primitive.

  • prims

    Returns the string value of a primitive attribute.

  • primsmap

    Returns a string from a list of strings in a primitive attribute.

  • primsnummap

    Returns the number of unique strings bound to a primitive attribute.

  • primuv

    Returns the value of a primitive attribute at a certain UV location.

  • primvals

    Returns components of a string array attribute.

  • print

    Prints a message to the console.

  • property

    Similar to ch(), but for render properties, with a default if the property doesn’t exist.

  • propertyf

    Evaluates a render property at a given frame.

  • propertys

    Evaluates the string value of a render property at the current time.

  • propertysop

    Evaluates a render property at the current time as a node path string.

  • propertysraw

    Evaluates the raw (unexpanded) string value of a render property at the current time.

  • propertyt

    Evaluates a render property at a given time.

  • pulse

    Returns 1 when a value is within a certain range.

  • pythonexprf

    Evaluates a Python expression, returning a float result.

  • pythonexprs

    Evaluates a Python expression, returning a string result.

  • qlinear

    Channel segment function: uses quaternions to interpolate.

  • quattomatrix

    Converts quaternion to a 3×3 rotation matrix.

  • quintic

    Channel segment function: smoothly interpolates slopes and accelerations.

  • rad

    Converts from degrees to radians.

  • rand

    Returns a pseudo-random number from 0 to 1.

  • raw

    Channel segment function.

  • realuv

    Converts unit UV to real UV.

  • relpath

    Returns the relative path of a file.

  • repeat

    Channel segment function: repeats animation from previous frames.

  • repeatt

    Channel segment function: repeats animation from previous frames.

  • res

    Returns the natural resolution of the image in a compositing node.

  • rgb

    Converts HSV values to RGB components.

  • rindex

    Finds the last occurrence of a pattern in a string.

  • rint

    Rounds to the nearest integer.

  • rotate

    Returns a 4×4 rotation matrix from an axis and angle.

  • rotaxis

    Returns a 4×4 rotation matrix from an angle and a vector.

  • round

    Rounds a number to the nearest integer.

  • rtrim

    Trims white sapce from the end of a string.

  • run

    Runs a string as an HScript command and returns the command’s output.

  • runb

    Runs a string as an HScript command and returns the command and error output.

  • rune

    Runs a string as an HScript command and returns any error output.

  • scale

    Takes three scaling values and returns a scale matrix.

  • scalefrommks

    Returns the scale factor converting from MKS units to the Houdini units.

  • scaletomks

    Returns the scale factor converting to MKS units from the Houdini units.

  • seampoints

    Lists all seam points in a surface node.

  • seqanim

    Returns 1 if a specified compositing node has an animated sequence.

  • seqend

    Returns the end frame of a compositing node’s image sequence.

  • seqlength

    Returns the number of frames in a compositing node’s image sequence.

  • seqstart

    Returns the start frame of a compositing node’s image sequence.

  • shopstring

    Returns the shader string generated by a shader.

  • sign

    Returns -1, 0, or 1 depending on the sign of the argument.

  • sin

    Returns the sine of the argument.

  • sinh

    Returns the hyperbolic sine of the argument.

  • smooth

    Takes a value and range and returns a smooth interpolation between 0 and 1.

  • snoise

    Generates sparse convolution 3D noise.

  • spknot

    Returns a knot value on a spline curve or surface.

  • spline

    Channel segment function: fits a curve to the keyframes.

  • sqrt

    Returns the square root of the argument.

  • stamp

    Returns a copy stamping floating point value.

  • stamps

    Returns a copy stamping string value.

  • strcasecmp

    Compares two strings, ignoring case.

  • strcasematch

    Returns 1 if a string matches a pattern, ignoring case.

  • strcat

    Returns the concatenation of two strings.

  • strcmp

    Compares two strings.

  • strdup

    Duplicates a string.

  • stripmatrix

    Strips non-essential characters from the string representation of a matrix or vector.

  • strlen

    Returns the number of characters in a string.

  • strmatch

    Returns 1 if a string matches a pattern, including case.

  • strreplace

    Replaces substrings with a new string.

  • strsplit

    Returns one component of a string split by some separators.

  • strsplitcount

    Returns the number of components in a string split by some separators.

  • sturb

    Generates spatially coherent 3D noise based on sparse convolution.

  • substr

    Returns a substring of a string.

  • surflen

    Returns the length of the 3D curve between two points on a surface.

  • system

    Runs a system command line and returns the output.

  • systemES

    Runs a system command line and returns the exit status.

  • systemRAW

    Runs a system command line and returns the output with no processing.

  • tan

    Returns the tangent of the argument.

  • tanh

    Returns the hyperbolic tangent of the argument.

  • tex

    Returns the interpolated color of a point on an on-disk texture map.

  • texni

    Returns the non-interpolated color of a point on an on-disk texture map.

  • tolower

    Returns the all-lowercase version of a string.

  • toupper

    Returns the all-uppercase version of a string.

  • translate

    Takes X, Y, and Z translation values and returns a translation matrix.

  • transpose

    Transposes a matrix.

  • trim

    Trims white sapce from either side of a string.

  • trunc

    Converts a number to an integer by truncating any fractional part, rounding towards 0.

  • turb

    Generates spatially coherent 3D noise.

  • uniqueval

    Returns a unique value of an integer attribute.

  • uniquevals

    Returns a unique value of a string attribute.

  • unituv

    Converts real UV to unit UV.

  • uvdist

    Returns the distance between parameteric locations on two primitives.

  • vangle

    Returns the angle between two vectors.

  • vector

    Converts a string specification into a vector.

  • vector3

    Converts three values into a 3-component vector.

  • vector4

    Converts four values into a 4-component vector.

  • vertex

    Returns the value of a vertex attribute.

  • vertexattriblist

    Returns a space-separated list of vertex attribute names.

  • vertexattribsize

    Returns the number of components in a vertex attribute.

  • vertexattribtype

    Returns the type of a vertex attribute.

  • vertexgrouplist

    Returns the list of vertex groups in a surface node.

  • vertexgroupmask

    Returns the list of vertex groups matching a pattern in a surface node.

  • vertexs

    Returns the string value of a vertex attribute.

  • vertexsmap

    Returns a string from a list of strings in a vertex attribute.

  • vertexsnummap

    Returns the number of unique strings bound to a point attribute.

  • vertexvals

    Returns components of a string array attribute.

  • vlength

    Returns the length of a vector.

  • vlength2

  • vmatch

    Channel segment function: matches the incoming and outgoing slopes.

  • vmatchin

    Channel segment function: matches the incoming slope.

  • vmatchout

    Channel segment function: matches the outgoing slope.

  • volumeaverage

    Returns the average value of all the voxels in a volume.

  • volumegradient

    Returns the gradient of a volume primitive at a specified location.

  • volumeindex

    Returns the value of a volume primitive at a specified voxel.

  • volumeindextopos

    Converts volume voxel coordinates to world-space coordinates.

  • volumemax

    Returns the maximum value of all voxels in a volume.

  • volumemin

    Returns the minimum value of all voxels in a volume.

  • volumepostoindex

    Converts world space coordinates to volume voxel coordinates.

  • volumeres

    Returns the resolution of a volume.

  • volumesample

    Returns the value of a volume at a specified position.

  • volumevoxeldiameter

    Returns the approximage diameter of a volume voxel in world space.

  • vorigin

    Returns a vector of an objects' transforms.

  • vpname

    Takes a viewer name and a viewport number and returns the viewport’s name.

  • vrorigin

    Returns a vector of an object’s rotations.

  • vscale

    Multiplies a vector by a scaling factor.

  • vset

    Creates a vector with each component set to the same value.

  • vsize

    Returns the number of elements in a vector.

  • vtorigin

    Returns a vector of an object’s translations.

  • wrap

    Wraps a value between a minimum and maximum.

  • xyzdist

    Returns the distance between a 3D coordinate and a primitive.