Houdini 16.5 VEX VEX Functions

atan2 VEX function

Returns the inverse tangent of y/x.

float  atan2(float y, float x)

Returns the principal value of the inverse tangent of y/x, using the signs of the two arguments to determine the quadrant of the result. The return value is in the range -π to π.

See also
trig

VEX Functions

Arrays

  • append

    Adds an item to an array or string.

  • argsort

    Returns the indices of a sorted version of an array.

  • array

    Efficiently creates an array from its arguments.

  • foreach

    Loops over the items in an array, with optional enumeration.

  • insert

    Inserts an item, array, or string into an array or string.

  • isvalidindex

    Checks if the index given is valid for the array or string given.

  • len

    Returns the length of an array.

  • pop

    Removes the last element of an array and returns it.

  • push

    Adds an item to an array.

  • removeindex

    Removes an item at the given index from an array.

  • removevalue

    Removes an item from an array.

  • reorder

    Reorders items in an array or string.

  • resize

    Sets the length of an array.

  • reverse

    Returns an array or string in reverse order.

  • slice

    Slices a sub-string or sub-array of a string or array.

  • sort

    Returns the array sorted in increasing order.

  • upush

    Adds a uniform item to an array.

Attributes and Intrinsics

  • addattrib

    Adds an attribute to a geometry.

  • adddetailattrib

    Adds a detail attribute to a geometry.

  • addpointattrib

    Adds a point attribute to a geometry.

  • addprimattrib

    Adds a primitive attribute to a geometry.

  • addvertexattrib

    Adds a vertex attribute to a geometry.

  • addvisualizer

    Appends to a geometry’s visualizer detail attribute.

  • attrib

    Reads the value of an attribute from geometry.

  • attribclass

    Returns the class of a geometry attribute.

  • attribsize

    Returns the size of a geometry attribute.

  • attribtype

    Returns the type of a geometry attribute.

  • attribtypeinfo

    Returns the transformation metadata of a geometry attribute.

  • detail

    Reads the value of a detail attribute value from a geometry.

  • detailattrib

    Reads a detail attribute value from a geometry.

  • detailattribsize

    Returns the size of a geometry detail attribute.

  • detailattribtype

    Returns the type of a geometry detail attribute.

  • detailattribtypeinfo

    Returns the type info of a geometry attribute.

  • detailintrinsic

    Reads the value of a detail intrinsic from a geometry.

  • findattribval

    Finds a primitive/point/vertex that has a certain attribute value.

  • findattribvalcount

    Returns number of elements where an integer or string attribute has a certain value.

  • getattrib

    Reads an attribute value from geometry, with validity check.

  • getattribute

    Copies the value of a geometry attribute into a variable and returns a success flag.

  • hasattrib

    Checks whether a geometry attribute exists.

  • hasdetailattrib

    Returns if a geometry detail attribute exists.

  • haspointattrib

    Returns if a geometry point attribute exists.

  • hasprimattrib

    Returns if a geometry prim attribute exists.

  • hasvertexattrib

    Returns if a geometry vertex attribute exists.

  • idtopoint

    Finds a point by its id attribute.

  • idtoprim

    Finds a primitive by its id attribute.

  • nametopoint

    Finds a point by its name attribute.

  • nametoprim

    Finds a primitive by its name attribute.

  • nuniqueval

    Returns the number of unique values from an integer or string attribute.

  • point

    Reads a point attribute value from a geometry.

  • pointattrib

    Reads a point attribute value from a geometry and outputs a success/fail flag.

  • pointattribsize

    Returns the size of a geometry point attribute.

  • pointattribtype

    Returns the type of a geometry point attribute.

  • pointattribtypeinfo

    Returns the type info of a geometry attribute.

  • prim

    Reads a primitive attribute value from a geometry.

  • prim_attribute

    Interpolates the value of an attribute at a certain parametric (u, v) position and copies it into a variable.

  • primarclen

    Evaluates the length of an arc on a primitive using parametric uv coordinates.

  • primattrib

    Reads a primitive attribute value from a geometry, outputting a success flag.

  • primattribsize

    Returns the size of a geometry prim attribute.

  • primattribtype

    Returns the type of a geometry prim attribute.

  • primattribtypeinfo

    Returns the type info of a geometry attribute.

  • primduv

    Returns position derivative on a primitive at a certain parametric (u, v) position.

  • primintrinsic

    Reads a primitive intrinsic from a geometry.

  • primuv

    Interpolates the value of an attribute at a certain parametric (uvw) position.

  • primuvconvert

    Convert parametric UV locations on curve primitives between different spaces.

  • setattrib

    Writes an attribute value to geometry.

  • setattribtypeinfo

    Sets the meaning of an attribute in geometry.

  • setdetailattrib

    Sets a detail attribute in a geometry.

  • setpointattrib

    Sets a point attribute in a geometry.

  • setprimattrib

    Sets a primitive attribute in a geometry.

  • setprimintrinsic

    Sets the value of a writeable primitive intrinsic attribute.

  • setvertexattrib

    Sets a vertex attribute in a geometry.

  • uniqueval

    Returns one of the set of unique values across all values for an int or string attribute.

  • uvsample

    Interpolates the value of an attribute at certain UV coordinates using a UV attribute.

  • vertex

    Reads a vertex attribute value from a geometry.

  • vertexattrib

    Reads a vertex attribute value from a geometry.

  • vertexattribsize

    Returns the size of a geometry vertex attribute.

  • vertexattribtype

    Returns the type of a geometry vertex attribute.

  • vertexattribtypeinfo

    Returns the type info of a geometry attribute.

BSDF

  • specular

    Returns a specular BSDF or computes specular shading.

BSDFs

  • albedo

    Returns the albedo (percentage of reflected light) for a bsdf given the outgoing light direction.

  • ashikhmin

    Returns a specular BSDF using the Ashikhmin shading model.

  • blinn

    Returns a Blinn BSDF or computes Blinn shading.

  • cone

    Returns a cone reflection BSDF.

  • cvex_bsdf

    Creates a bsdf object from two CVEX shader strings.

  • diffuse

    Returns a diffuse BSDF or computes diffuse shading.

  • eval_bsdf

    Evaluates a bsdf given two vectors.

  • getbounces

  • hair

    Returns a BSDF for shading hair.

  • henyeygreenstein

    Returns an anisotropic volumetric BSDF, which can scatter light forward or backward.

  • isotropic

    Returns an isotropic BSDF, which scatters light equally in all directions.

  • mask_bsdf

    Returns new BSDF that only includes the components specified by the mask.

  • normal_bsdf

    Returns the normal for the diffuse component of a BSDF.

  • phong

    Returns a Phong BSDF or computes Phong shading.

  • phonglobe

  • sample_bsdf

    Samples a BSDF.

  • solid_angle

    Computes the solid angle (in steradians) a BSDF function subtends.

  • split_bsdf

    Splits a bsdf into its component lobes.

  • sssapprox

    Creates an approximate SSS BSDF.

CHOP

  • chadd

    Adds new channels to a CHOP node.

  • chattr

    Reads from a CHOP attribute.

  • chattrnames

    Reads CHOP attribute names of a given attribute class from a CHOP input.

  • chend

    Returns the sample number of the last sample in a given CHOP input.

  • chendf

    Returns the frame corresponding to the last sample of the input specified.

  • chendt

    Returns the time corresponding to the last sample of the input specified.

  • chindex

    Returns the channel index from a input given a channel name.

  • chinput

    Returns the value of a channel at the specified sample.

  • chinputlimits

    Computes the minimum and maximum value of samples in an input channel.

  • chnames

    Returns all the CHOP channel names of a given CHOP input.

  • chnumchan

    Returns the number of channels in the input specified.

  • chrate

    Returns the sample rate of the input specified.

  • chreadbuf

    Returns the value of CHOP context temporary buffer at the specified index.

  • chremove

    Removes channels from a CHOP node.

  • chremoveattr

    Removes a CHOP attribute.

  • chrename

    Renames a CHOP channel.

  • chresizebuf

    Resize the CHOP context temporary buffer

  • chsetattr

    Sets the value of a CHOP attribute.

  • chsetlength

    Sets the length of the CHOP channel data.

  • chsetrate

    Sets the sampling rate of the CHOP channel data.

  • chsetstart

    Sets the CHOP start sample in the channel data.

  • chstart

    Returns the start sample of the input specified.

  • chstartf

    Returns the frame corresponding to the first sample of the input specified.

  • chstartt

    Returns the time corresponding to the first sample of the input specified.

  • chwritebuf

    Writes a value of CHOP context temporary buffer at the specified index.

  • isframes

    Returns 1 if the Vex CHOP’s Unit Menu is currently set to 'frames', 0 otherwise.

  • issamples

    Returns 1 if the Vex CHOP’s Unit Menu is currently set to 'samples', 0 otherwise.

  • isseconds

    Returns 1 if the Vex CHOP’s Unit Menu is currently set to 'seconds', 0 otherwise.

  • ninputs

    Returns the number of inputs.

color

  • blackbody

    Compute the color value of an incandescent black body.

  • ctransform

    Transforms between color spaces.

  • luminance

    Compute the luminance of the RGB color specified by the parameters.

Conversion

  • atof

    Converts a string to a float.

  • atoi

    Converts a string to an integer.

  • cracktransform

    Depending on the value of c, returns the translate (c=0), rotate (c=1), scale (c=2), or shears (c=3) component of the transform (xform).

  • degrees

    Converts the argument from radians into degrees.

  • eulertoquaternion

    Creates a vector4 representing a quaternion from euler angles.

  • hsvtorgb

    Convert HSV color space into RGB color space.

  • qconvert

    Converts a quaternion represented by a vector4 to a matrix3 representation.

  • radians

    Converts the argument from degrees into radians.

  • rgbtohsv

    Convert RGB color space to HSV color space.

  • rgbtoxyz

    Convert a linear sRGB triplet to CIE XYZ tristimulus values.

  • serialize

    Flattens an array of vector or matrix types into an array of floats.

  • unserialize

    Turns a flat array of floats into an array of vectors or matrices.

  • xyztorgb

    Convert CIE XYZ tristimulus values to a linear sRGB triplet.

Crowds

displace

  • dimport

    Reads a variable from the displacement shader for the surface.

File I/O

  • file_stat

    Returns file system status for a given file.

Fuzzy Logic

Geometry

  • addpoint

    Adds a point to the geometry.

  • addprim

    Adds a primitive to the geometry.

  • addvertex

    Adds a vertex to a primitive in a geometry.

  • clip

    Clip the line segment between p0 and p1.

  • expandedgegroup

  • geoself

    Returns a handle to the current geometry.

  • geounwrap

    Returns an oppath: string to unwrap the geometry in-place.

  • inedgegroup

    Returns 1 if the edge specified by the point pair is in the group specified by the string.

  • intersect

    This function computes the first intersection of a ray with geometry.

  • intersect_all

    Computes all intersections of the specified ray with geometry.

  • minpos

    Finds the closest position on the surface of a geometry.

  • nearpoint

    Finds the closest point in a geometry.

  • nearpoints

    Finds the all the closest point in a geometry.

  • nedgesgroup

    Returns the number of edges in the group.

  • neighbour

    Returns the point number of the next point connected to a given point.

  • neighbourcount

    Returns the number of points that are connected to the specified point.

  • neighbours

    Returns an array of the point numbers of the neighbours of a point.

  • npoints

    Returns the number of points in the input or geometry file.

  • nprimitives

    Returns the number of primitives in the input or geometry file.

  • nvertices

    Returns the number of vertices in the input or geometry file.

  • nverticesgroup

    Returns the number of vertices in the group.

  • pointprims

    Returns the list of primitives containing a point.

  • pointvertex

    Returns a linear vertex number of a point in a geometry.

  • pointvertices

    Returns the list of vertices connected to a point.

  • primfind

    Returns a list of primitives potentially intersecting a given bounding box.

  • primpoint

    Converts a primitive/vertex pair into a point number.

  • primpoints

    Returns the list of points on a primitive.

  • primvertex

    Converts a primitive/vertex pair into a linear vertex.

  • primvertexcount

    Returns number of vertices in a primitive in a geometry.

  • primvertices

    Returns the list of vertices on a primitive.

  • removepoint

    Removes a point from the geometry.

  • removeprim

    Removes a primitive from the geometry.

  • setedgegroup

    Sets edge group membership in a geometry.

  • setprimvertex

    Rewires a vertex in the geometry to a different point.

  • setvertexpoint

    Rewires a vertex in the geometry to a different point.

  • uvintersect

    This function computes the intersection of the specified ray with the geometry in uv space.

  • vertexindex

    Converts a primitive/vertex pair into a linear vertex.

  • vertexnext

    Returns the linear vertex number of the next vertex sharing a point with a given vertex.

  • vertexpoint

    Returns the point number of linear vertex in a geometry.

  • vertexprev

    Returns the linear vertex number of the previous vertex sharing a point with a given vertex.

  • vertexprim

    Returns the number of the primitive containing a given vertex.

  • vertexprimindex

    Converts a linear vertex index into a primitive vertex number.

groups

  • expandpointgroup

  • expandprimgroup

  • inpointgroup

    Returns 1 if the point specified by the point number is in the group specified by the string.

  • inprimgroup

    Returns 1 if the primitive specified by the primitive number is in the group specified by the string.

  • invertexgroup

    Returns 1 if the vertex specified by the vertex number is in the group specified by the string.

  • npointsgroup

    Returns the number of points in the group.

  • nprimitivesgroup

    Returns the number of primitives in the group.

  • setpointgroup

    Adds or removes a point to/from a group in a geometry.

  • setprimgroup

    Adds or removes a primitive to/from a group in a geometry.

  • setvertexgroup

    Adds or removes a vertex to/from a group in a geometry.

Half-edges

  • hedge_dstpoint

    Returns the destination point of a half-edge.

  • hedge_dstvertex

    Returns the destination vertex of a half-edge.

  • hedge_equivcount

    Returns the number of half-edges equivalent to a given half-edge.

  • hedge_isequiv

    Determines whether a two half-edges are equivalent (represent the same edge).

  • hedge_isprimary

    Determines whether a half-edge number corresponds to a primary half-edge.

  • hedge_isvalid

    Determines whether a half-edge number corresponds to a valid half-edge.

  • hedge_next

    Returns the half-edge that follows a given half-edge in its polygon.

  • hedge_nextequiv

    Returns the next half-edges equivalent to a given half-edge.

  • hedge_postdstpoint

    Returns the point into which the vertex following the destination vertex of a half-edge in its primitive is wired.

  • hedge_postdstvertex

    Returns the vertex following the destination vertex of a half-edge in its primitive.

  • hedge_presrcpoint

    Returns the point into which the vertex that precedes the source vertex of a half-edge in its primitive is wired.

  • hedge_presrcvertex

    Returns the vertex that precedes the source vertex of a half-edge in its primitive.

  • hedge_prev

    Returns the half-edge that precedes a given half-edge in its polygon.

  • hedge_prim

    Returns the primitive that contains a half-edge.

  • hedge_primary

    Returns the primary half-edge equivalent to a given half-edge.

  • hedge_srcpoint

    Returns the source point of a half-edge.

  • hedge_srcvertex

    Returns the source vertex of a half-edge.

  • pointedge

    Finds and returns a half-edge with the given endpoints.

  • pointhedge

    Finds and returns a half-edge with a given source point or with given source and destination points.

  • pointhedgenext

    Returns the next half-edge with the same source as a given half-edge.

  • primhedge

    Returns one of the half-edges contained in a primitive.

  • vertexhedge

    Returns the half-edge which has a vertex as source.

Image Processing

  • accessframe

    Tells the COP manager that you need access to the given frame.

  • alphaname

    Returns the default name of the alpha plane (as it appears in the compositor preferences).

  • binput

    Samples a 2×2 pixel block around the given UV position, and bilinearly interpolates these pixels.

  • bumpname

    Returns the default name of the bump plane (as it appears in the compositor preferences).

  • chname

    Returns the name of a numbered channel.

  • cinput

    Samples the exact (unfiltered) pixel color at the given coordinates.

  • colorname

    Returns the default name of the color plane (as it appears in the compositor preferences).

  • depthname

    Returns the default name of the depth plane (as it appears in the compositor preferences).

  • dsmpixel

    Reads the z-records stored in a pixel of a deep shadow map or deep camera map.

  • finput

    Returns fully filtered pixel input.

  • hasmetadata

    Queries if metadata exists on a composite operator.

  • hasplane

    Returns 1 if the plane specified by the parameter exists in this COP.

  • iaspect

    Returns the aspect ratio of the specified input.

  • ichname

    Returns the channel name of the indexed plane of the given input.

  • iend

    Returns the last frame of the specified input.

  • iendtime

    Returns the end time of the specified input.

  • ihasplane

    Returns 1 if the specified input has a plane named planename.

  • inumplanes

    Returns the number of planes in the given input.

  • iplaneindex

    Returns the index of the plane named 'planename' in the specified input.

  • iplanename

    Returns the name of the plane specified by the planeindex of the given input

  • iplanesize

    Returns the number of components in the plane named planename in the specified input.

  • irate

    Returns the frame rate of the specified input.

  • istart

    Returns the starting frame of the specified input.

  • istarttime

    Returns the start time of the specified input.

  • ixres

    Returns the X resolution of the specified input.

  • iyres

    Returns the Y resolution of the specified input.

  • lumname

    Returns the default name of the luminence plane (as it appears in the compositor preferences).

  • maskname

    Returns the default name of the mask plane (as it appears in the compositor preferences).

  • metadata

    Returns a metadata value from a composite operator.

  • ninput

    Reads a component from a pixel and its eight neighbors.

  • normalname

    Returns the default name of the normal plane (as it appears in the compositor preferences).

  • planeindex

    Returns the index of the plane specified by the parameter, starting at zero.

  • planename

    Returns the name of the plane specified by the index (e.

  • planesize

    Returns the number of components in the plane (1 for scalar planes and up to 4 for vector planes).

  • pointname

    Returns the default name of the point plane (as it appears in the compositor preferences).

  • velocityname

    Returns the default name of the velocity plane (as it appears in the compositor preferences).

Interpolation

  • ckspline

    Samples a Catmull-Rom (Cardinal) spline defined by position/value keys.

  • clamp

    Returns value clamped between min and max.

  • cspline

    Samples a Catmull-Rom (Cardinal) spline defined by uniformly spaced keys.

  • efit

    Takes the value in one range and shifts it to the corresponding value in a new range.

  • fit

    Takes the value in one range and shifts it to the corresponding value in a new range.

  • fit01

    Takes the value in the range (0, 1) and shifts it to the corresponding value in a new range.

  • fit10

    Takes the value in the range (1, 0) and shifts it to the corresponding value in a new range.

  • fit11

    Takes the value in the range (-1, 1) and shifts it to the corresponding value in a new range.

  • lerp

    Performs bilinear interpolation between the values.

  • lkspline

    Samples a polyline between the key points.

  • lspline

    Samples a polyline defined by linearly spaced values.

  • slerp

    Quaternion blend between q1 and q2 based on the bias.

  • smooth

    Computes ease in/out interpolation between values.

light

  • ambient

    Returns the color of ambient light in the scene.

  • atten

    Computes attenuated falloff.

  • fastshadow

    Sends a ray from the position P along the direction specified by the direction D.

  • filtershadow

    Sends a ray from the position P along direction D.

Math

  • Du

    Returns the derivative of the given value with respect to U.

  • Dv

    Returns the derivative of the given value with respect to V.

  • Dw

    Returns the derivative of the given value with respect to the 3rd axis (for volume rendering).

  • abs

    Returns the absolute value of the argument.

  • acos

    Returns the inverse cosine of the argument.

  • asin

    Returns the inverse sine of the argument.

  • atan

    Returns the inverse tangent of the argument.

  • atan2

    Returns the inverse tangent of y/x.

  • avg

    Returns the average value of the input(s)

  • cbrt

    Returns the cube root of the argument.

  • ceil

    Returns the smallest integer greater than or equal to the argument.

  • cos

    Returns the cosine of the argument.

  • cosh

    Returns the hyperbolic cosine of the argument.

  • cross

    Returns the cross product between the two vectors.

  • determinant

    Computes the determinant of the matrix.

  • dot

    Returns the dot product between the arguments.

  • eigenvalues

    Computes the eigenvalues of a 3×3 matrix.

  • erf

    Gauss error function.

  • erf_inv

    Inverse Gauss error function.

  • erfc

    Gauss error function’s complement.

  • exp

    Returns the exponential function of the argument.

  • floor

    Returns the largest integer less than or equal to the argument.

  • frac

    Returns the fractional component of the floating point number.

  • ident

    Returns an identity matrix.

  • invert

    Inverts a matrix.

  • isfinite

    Checks whether a value is a normal finite number.

  • isnan

    Checks whether a value is not a number.

  • kspline

    Returns an interpolated value along a curve defined by a basis and key/position pairs.

  • length

    Returns the magnitude of a vector.

  • length2

    Returns the squared distance of the vector or vector4.

  • log

    Returns the natural logarithm of the argument.

  • log10

    Returns the logarithm (base 10) of the argument.

  • makebasis

    Creates an orthonormal basis given a z-axis vector.

  • max

  • min

  • normalize

    Returns a normalized vector.

  • outerproduct

    Returns the outer product between the arguments.

  • planesphereintersect

    Computes the intersection of a 3D sphere and an infinite 3D plane.

  • pow

    Raises the first argument to the power of the second argument.

  • predicate_incircle

    Determines if a point is inside or outside a triangle circumcircle.

  • predicate_insphere

    Determines if a point is inside or outside a tetrahedron circumsphere.

  • predicate_orient2d

    Determines the orientation of a point with respect to a line.

  • predicate_orient3d

    Determines the orientation of a point with respect to a plane.

  • product

    Returns the product of a list of numbers.

  • ptlined

    This function returns the closest distance between the point Q and a finite line segment between points P0 and P1.

  • qdistance

    Finds distance between two quaternions.

  • qinvert

    Inverts a quaternion rotation.

  • qmultiply

    Multiplies two quaternions and returns the result.

  • qrotate

    Rotates a vector by a quaternion.

  • quaternion

    Creates a vector4 representing a quaternion.

  • resample_linear

  • rint

    Rounds the number to the closest whole number.

  • shl

    Bit-shifts an integer left.

  • shr

    Bit-shifts an integer right.

  • shrz

    Bit-shifts an integer right.

  • 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.

  • slideframe

    Finds the normal component of frame slid along a curve.

  • solvecubic

    Solves a cubic function returning the number of real roots.

  • solvepoly

    Finds the real roots of a polynomial.

  • solvequadratic

    Solves a quadratic function returning the number of real roots.

  • spline

    Samples a value along a polyline or spline curve.

  • sqrt

    Returns the square root of the argument.

  • sum

    Returns the sum of a list of numbers.

  • tan

    Returns the trigonometric tangent of the argument

  • tanh

    Returns the hyperbolic tangent of the argument

  • transpose

    Transposes the given matrix.

  • trunc

    Removes the fractional part of a floating point number.

measure

  • distance

    Returns the distance between two points.

  • distance2

    Returns the squared distance between the two points.

  • getbbox

    Sets two vectors to the minimum and maximum corners of the bounding box for the geometry.

  • getbbox_center

    Returns the center of the bounding box for the geometry.

  • getbbox_max

    Returns the maximum of the bounding box for the geometry.

  • getbbox_min

    Returns the minimum of the bounding box for the geometry.

  • getbbox_size

    Returns the size of the bounding box for the geometry.

  • getbounds

    Returns the bounding box of the geometry specified by the filename.

  • getpointbbox

    Sets two vectors to the minimum and maximum corners of the bounding box for the geometry.

  • getpointbbox_center

    Returns the center of the bounding box for the geometry.

  • getpointbbox_max

    Returns the maximum of the bounding box for the geometry.

  • getpointbbox_min

    Returns the minimum of the bounding box for the geometry.

  • getpointbbox_size

    Returns the size of the bounding box for the geometry.

  • planepointdistance

    Computes the distance and closest point of a point to an infinite plane.

  • relbbox

    Returns the relative position of the point given with respect to the bounding box of the geometry.

  • relpointbbox

    Returns the relative position of the point given with respect to the bounding box of the geometry.

  • uvdist

    Finds the distance of a uv coordinate to a geometry in uv space.

  • xyzdist

    Finds the distance of a point to a geometry.

metaball

  • metaimport

    Once you get a handle to a metaball using metastart and metanext, you can query attributes of the metaball with metaimport.

  • metamarch

    Takes the ray defined by p0 and p1 and partitions it into zero or more sub-intervals where each interval intersects a cluster of metaballs from filename.

  • metanext

    Iterate to the next metaball in the list of metaballs returned by the metastart() function.

  • metastart

    Open a geometry file and return a "handle" for the metaballs of interest, at the position p.

  • metaweight

    Returns the metaweight of the geometry at position p.

Nodes

  • addvariablename

    Adds a mapping for an attribute to a local variable.

  • ch

    Evaluates a channel (or parameter) and return its value.

  • ch2

    Evaluates a channel (or parameter) and return its value.

  • ch3

    Evaluates a channel (or parameter) and return its value.

  • ch4

    Evaluates a channel (or parameter) and return its value.

  • 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 channel (or parameter) and return its value.

  • chi

    Evaluates a channel (or parameter) and return its value.

  • chp

    Evaluates a channel (or parameter) and return its value.

  • chramp

    Evaluates a ramp parameter and return its value.

  • chs

    Evaluates a channel (or parameter) and return its value.

  • chsraw

    Returns the raw string channel (or parameter).

  • chu

    Evaluates a channel or parameter, and return its value.

  • chv

    Evaluates a channel or parameter, and return its value.

  • isconnected

    Returns 1 if input_number is connected, or 0 if the input is not connected.

  • opfullpath

    Returns the full path for the given relative path

  • opparentbonetransform

    Returns the parent bone transform associated with an OP.

  • opparenttransform

    Returns the parent transform associated with an OP.

  • opparmtransform

    Returns the parm transform associated with an OP.

  • oppreconstrainttransform

    Returns the preconstraint transform associated with an OP.

  • oppretransform

    Returns the pretransform associated with an OP.

  • optransform

    Returns the transform associated with an OP.

Noise and Randomness

  • anoise

    Generates "alligator" noise.

  • curlnoise

    Computes divergence free noise based on Perlin noise.

  • curlnoise2d

    Computes 2d divergence free noise based on Perlin noise.

  • curlxnoise

    Computes divergence free noise based on Simplex noise.

  • curlxnoise2d

    Computes 2d divergence free noise based on simplex noise.

  • cwnoise

    Generates Worley (cellular) noise using a Chebyshev distance metric.

  • flownoise

    Generates 1D and 3D Perlin Flow Noise from 3D and 4D data.

  • flowpnoise

    There are two forms of Perlin-style noise: a non-periodic noise which changes randomly throughout N-dimensional space, and a periodic form which repeats over a given range of space.

  • hscript_noise

    Generates noise matching the output of the Hscript noise() expression function.

  • hscript_rand

    Produces the exact same results as the Houdini expression function of the same name.

  • hscript_snoise

  • hscript_sturb

  • hscript_turb

    Generates turbulence matching the output of the HScript turb() expression function.

  • mwnoise

    Generates Worley (cellular) noise using a Manhattan distance metric.

  • noise

    There are two forms of Perlin-style noise: a non-periodic noise which changes randomly throughout N-dimensional space, and a periodic form which repeats over a given range of space.

  • noised

    Derivatives of Perlin Noise.

  • nrandom

    Non-deterministic random number generation function.

  • onoise

    These functions are similar to wnoise and vnoise.

  • pnoise

    There are two forms of Perlin-style noise: a non-periodic noise which changes randomly throughout N-dimensional space, and a periodic form which repeats over a given range of space.

  • rand

    Creates a random number between 0 and 1 from a seed.

  • random

    Generate a random number based on the position in 1-4D space.

  • random_fhash

    Hashes floating point numbers to integers.

  • random_ihash

    Hashes integer numbers to integers.

  • random_shash

    Hashes a string to an integer.

  • random_sobol

    Generate a uniformly distributed random number.

  • snoise

    These functions are similar to wnoise.

  • vnoise

    Generates Voronoi (cellular) noise.

  • wnoise

    Generates Worley (cellular) noise.

  • xnoise

    Simplex noise is very close to Perlin noise, except with the samples on a simplex mesh rather than a grid. This results in less grid artifacts. It also uses a higher order bspline to provide better derivatives.

  • xnoised

    Derivatives of Simplex Noise.

normals

  • computenormal

    In shading contexts, computes a normal. In the SOP contexts, sets how/whether to recompute normals.

  • prim_normal

    Returns the normal of the primitive (prim_number) at parametric location u, v.

Open Color IO

  • ocio_activedisplays

    Returns the names of active displays supported in Open Color IO

  • ocio_activeviews

    Returns the names of active views supported in Open Color IO

  • ocio_import

    Imports attributes from OpenColorIO spaces.

  • ocio_roles

    Returns the names of roles supported in Open Color IO

  • ocio_spaces

    Returns the names of color spaces supported in Open Color IO.

  • ocio_transform

    Transform colors using Open Color IO

particles

  • filamentsample

    Samples the velocity field defined by a set of vortex filaments.

Point Clouds and 3D Images

  • mattrib

    Returns the value of the point attribute for the metaballs if metaball geometry is specified to i3dgen.

  • mdensity

    Returns the density of the metaball field if metaball geometry is specified to i3dgen.

  • mspace

    Transforms the position specified into the "local" space of the metaball.

  • pcclose

    This function closes the handle associated with a pcopen function.

  • pcconvex

  • pcexport

    Writes data to a point cloud inside a pciterate or a pcunshaded loop.

  • pcfarthest

    Returns the distance to the farthest point found in the search performed by pcopen.

  • pcfilter

    Filters points found by pcopen using a simple reconstruction filter.

  • pcfind

    Returns a list of closest points from a file.

  • pcfind_radius

    Returns a list of closest points from a file taking into account their radii.

  • pcgenerate

    Generates a point cloud.

  • pcimport

    Imports channel data from a point cloud inside a pciterate or a pcunshaded loop.

  • pcimportbyidx3

    Imports channel data from a point cloud outside a pciterate or a pcunshaded loop.

  • pcimportbyidx4

    Imports channel data from a point cloud outside a pciterate or a pcunshaded loop.

  • pcimportbyidxf

    Imports channel data from a point cloud outside a pciterate or a pcunshaded loop.

  • pcimportbyidxi

    Imports channel data from a point cloud outside a pciterate or a pcunshaded loop.

  • pcimportbyidxp

    Imports channel data from a point cloud outside a pciterate or a pcunshaded loop.

  • pcimportbyidxs

    Imports channel data from a point cloud outside a pciterate or a pcunshaded loop.

  • pcimportbyidxv

    Imports channel data from a point cloud outside a pciterate or a pcunshaded loop.

  • pciterate

    This function can be used to iterate over all the points which were found in the pcopen query.

  • pcnumfound

    This node returns the number of points found by pcopen.

  • pcopen

    Returns a handle to a point cloud file.

  • pcopenlod

    Returns a handle to a point cloud file.

  • pcsampleleaf

    Changes the current iteration point to a leaf descendant of the current aggregate point.

  • pcsize

  • pcunshaded

    Iterate over all of the points of a read-write channel which haven’t had any data written to the channel yet.

  • pcwrite

    Writes data to a point cloud file.

  • pgfind

    Returns a list of closest points from a file.

  • photonmap

    Samples a color from a photon map.

  • texture3d

    Returns the value of the 3d image at the position specified by P.

  • texture3dBox

    This function queries the 3D texture map specified and returns the bounding box information of the file.

Sampling

  • create_cdf

    Creates a CDF from an array of input PDF values.

  • create_pdf

    Creates a PDF from an array of input values.

  • limit_sample_space

    Limits a unit value in a way that maintains uniformity and in-range consistency.

  • newsampler

    Initializes a sampling sequence for the nextsample function.

  • nextsample

  • sample_cauchy

    Samples the Cauchy (Lorentz) distribution.

  • sample_cdf

    Samples a CDF.

  • sample_circle_arc

    Generates a uniform unit vector2, within maxangle of center, given a uniform number between 0 and 1.

  • sample_circle_edge_uniform

    Generates a uniform unit vector2, given a uniform number between 0 and 1.

  • sample_circle_slice

    Generates a uniform vector2 with length < 1, within maxangle of center, given a vector2 of uniform numbers between 0 and 1.

  • sample_circle_uniform

    Generates a uniform vector2 with length < 1, given a vector2 of uniform numbers between 0 and 1.

  • sample_direction_cone

    Generates a uniform unit vector, within maxangle of center, given a vector2 of uniform numbers between 0 and 1.

  • sample_direction_uniform

    Generates a uniform unit vector, given a vector2 of uniform numbers between 0 and 1.

  • sample_discrete

    Returns an integer, either uniform or weighted, given a uniform number between 0 and 1.

  • sample_exponential

    Samples the exponential distribution.

  • sample_geometry

    Samples geometry in the scene and returns information from the shaders of surfaces that were sampled.

  • sample_hemisphere

    Generates a unit vector, optionally biased, within a hemisphere, given a vector2 of uniform numbers between 0 and 1.

  • sample_hypersphere_cone

    Generates a uniform vector4 with length < 1, within maxangle of center, given a vector4 of uniform numbers between 0 and 1.

  • sample_hypersphere_uniform

    Generates a uniform vector4 with length < 1, given a vector4 of uniform numbers between 0 and 1.

  • sample_light

    Samples a 3D position on a light source and runs the light shader at that point.

  • sample_lognormal

    Samples the log-normal distribution based on parameters of the underlying normal distribution.

  • sample_lognormal_by_median

    Samples the log-normal distribution based on median and standard deviation.

  • sample_normal

    Samples the normal (Gaussian) distribution.

  • sample_orientation_cone

    Generates a uniform unit vector4, within maxangle of center, given a vector of uniform numbers between 0 and 1.

  • sample_orientation_uniform

    Generates a uniform unit vector4, given a vector of uniform numbers between 0 and 1.

  • sample_photon

    Samples a 3D position on a light source and runs the light shader at that point.

  • sample_sphere_cone

    Generates a uniform vector with length < 1, within maxangle of center, given a vector of uniform numbers between 0 and 1.

  • sample_sphere_uniform

    Generates a uniform vector with length < 1, given a vector of uniform numbers between 0 and 1.

  • sampledisk

    Warps uniform random samples to a disk.

  • variance

    Computes the mean value and variance for a value.

Sensor Input

Shading and Rendering

  • area

    Returns the area of the micropolygon containing a variable such as P.

  • blinnBRDF

  • bouncelabel

  • bouncemask

  • diffuseBRDF

  • filterstep

    Returns the anti-aliased weight of the step function.

  • fresnel

    Computes the fresnel reflection/refraction contributions given an incoming vector, surface normal (both normalized), and an index of refraction (eta).

  • frontface

    If dot(I, Nref) is less than zero, N will be negated.

  • gather

    Sends rays into the scene and returns information from the shaders of surfaces hit by the rays.

  • getblurP

    Returns the blurred point position (P) vector at a fractional time within the motion blur exposure.

  • getcomponents

  • getderiv

    Evaluates surface derivatives of an attribute.

  • getfogname

    Returns the name of the current object whose shader is being run.

  • getglobalraylevel

    Returns the depth of the ray tree for computing global illumination.

  • getgroupid

    Returns group id containing current primitive.

  • getlight

    Returns a light struct for the specified light identifier.

  • getlightid

    Returns the light id for a named light (or -1 for an invalid name).

  • getlightname

    Returns the name of the current light when called from within an illuminance loop, or converts an integer light ID into the light’s name.

  • getlights

    Returns an array of light identifiers for the currently shaded surface.

  • getlightscope

    Returns a selection of lights that illuminate a given material.

  • getlocalcurvature

    Evaluates local curvature of primitive grid, using the same curvature evaluation method as Measure SOPs.

  • getmaterial

    Returns a material struct for the current surface.

  • getmaterialid

    Returns material id of shaded primitive.

  • getobjectid

    Returns the object id for the current shading context.

  • getobjectname

    Returns the name of the current object whose shader is being run.

  • getphotonlight

    Returns the integer ID of the light being used for photon shading.

  • getprimid

    Returns the number of the current primitive.

  • getptextureid

    Returns the ptexture face id for the current primitive.

  • getraylevel

    Returns the depth of the ray tree for the current shading.

  • getrayweight

    Returns an approximation to the contribution of the ray to the final pixel color.

  • getsamplestore

    Looks up sample data in a channel, referenced by a point.

  • getscope

    Returns a selection of objects visible to rays for a given material.

  • getsmoothP

    Returns modified surface position based on a smoothing function.

  • getuvtangents

    Evaluates UV tangents at a point on an arbitrary object.

  • gradient

    Returns the gradient of a field.

  • haslight

    Returns whether a light illuminates the given material.

  • illuminance

    Loops through all light sources in the scene, calling the light shader for each light source to set the Cl and L global variables.

  • interpolate

    Interpolates a value across the currently shaded micropolygon.

  • intersect_lights

    Finds the nearest intersection of a ray with any of a list of (area) lights and runs the light shader at the intersection point.

  • irradiance

    Computes irradiance (global illumination) at the point P with the normal N.

  • isfogray

    Returns 1 if the shader is being called to evaluate illumination for fog objects, or 0 if the light or shadow shader is being called to evaluate surface illumination.

  • israytracing

    Indicates whether a shader is being executed for ray tracing.

  • isshadowray

    Returns 1 if the shader is being called to evaluate opacity for shadow rays, or 0 if the shader is being called to evaluate for surface color.

  • isuvrendering

    Indicats whether the shader is being evaulated while doing UV rendering (e.g. texture unwrapping)

  • lightbounces

    Returns the bounce mask for a light struct.

  • lightid

    Returns the light id for a light struct.

  • limport

    Imports a variable from the light shader for the surface.

  • matchvex_blinn

    Returns a BSDF that matches the output of the traditional VEX blinn function.

  • matchvex_specular

    Returns a BSDF that matches the output of the traditional VEX specular function.

  • nbouncetypes

  • occlusion

    Computes ambient occlusion.

  • pathtrace

    Computes global illumination using PBR for secondary bounces.

  • phongBRDF

  • rayhittest

    Sends a ray from the position P along the direction D.

  • rayimport

    Imports a value sent by a shader in a gather loop.

  • reflect

    Returns the vector representing the reflection of the direction against the normal.

  • reflectlight

    Computes the amount of reflected light which hits the surface.

  • refract

    Returns the refraction ray given an incoming direction, the normalized normal and an index of refraction.

  • refractlight

    Computes the illumination of surfaces refracted by the current surface.

  • renderstate

    Queries the renderer for a named property.

  • resolvemissedray

    Returns the background color for rays that exit the scene.

  • scatter

    Evaluates a scattering event through the domain of a geometric object.

  • setcurrentlight

    Sets the current light

  • setsamplestore

    Stores sample data in a channel, referenced by a point.

  • shadow

    Calls shadow shaders for the current light source.

  • shadow_light

    Executes the shadow shader for a given light and returns the amount of shadowing as a multiplier of the shaded color.

  • shimport

    Imports a variable from the shadow shader for the surface.

  • simport

    Imports a variable sent by a surface shader in an illuminance loop.

  • specularBRDF

    Returns the computed BRDFs for the different lighting models used in VEX shading.

  • storelightexport

    Stores exported data for a light.

  • switch

    Use a different bsdf for direct or indirect lighting.

  • trace

    Sends a ray from P along the normalized vector D.

  • translucent

    Returns a Lambertian translucence BSDF.

  • uvunwrap

    Computes the position and normal at given (u, v) coordinates.

  • wireblinn

  • wirediffuse

  • writepixel

    Writes color information to a pixel in the output image

Strings

  • chr

    Converts an unicode codepoint to a UTF8 string.

  • concat

    Concatenate all the strings specified to form a single string.

  • endswith

    Indicates the string ends with the specified string.

  • find

    Finds an item in an array or string.

  • isalpha

    Returns 1 if all the characters in the string are alphabetic

  • isdigit

    Returns 1 if all the characters in the string are numeric

  • itoa

    Converts an integer to a string.

  • join

    Concatenate all the strings of an array inserting a common spacer.

  • lstrip

    Strips leading whitespace from a string.

  • match

    This function returns 1 if the subject matches the pattern specified, or 0 if the subject doesn’t match.

  • opdigits

    Returns the integer value of the last sequence of digits of a string

  • ord

    Converts an UTF8 string into a codepoint.

  • pluralize

    Converts an English noun to its plural.

  • re_find

    Matches a regular expression in a string

  • re_findall

    Finds all instances of the given regular expression in the string

  • re_match

    Returns 1 if the entire input string matches the expression

  • re_replace

    Replaces instances of regex_find with regex_replace

  • re_split

    Splits the given string based on regex match.

  • relativepath

    Computes the relative path for two full paths.

  • rstrip

    Strips trailing whitespace from a string.

  • split

    Splits a string into tokens.

  • splitpath

    Splits a file path into the directory and name parts.

  • sprintf

    Formats a string like printf but returns the result as a string instead of printing it.

  • startswith

    Returns 1 if the string starts with the specified string.

  • strip

    Strips leading and trailing whitespace from a string.

  • strlen

    Returns the length of the string.

  • titlecase

    Returns a string that is the titlecase version of the input string.

  • tolower

    Converts all charactors in string to lower case

  • toupper

    Convers all charactors in string to upper case

Subdivision Surfaces

Tetrahedrons

  • tet_adjacent

    Returns primitive number of an adjacent tetrahedron.

  • tet_faceindex

    Returns vertex indices of each face of a tetrahedron.

Texturing

  • colormap

    Looks up a (filtered) color from a texture file.

  • depthmap

    The depthmap functions work on an image which was rendered as a z-depth image from mantra.

  • environment

    Returns the color of the environment texture.

  • expand_udim

    Perform UDIM or UVTILE texture filename expansion.

  • ocean_sample

    Evaluates an ocean spectrum and samples the result at a given time and location.

  • ptexture

    Computes a filtered sample from a ptex texture map. Use texture instead.

  • rawcolormap

    Looks up an unfiltered color from a texture file.

  • shadowmap

    The shadowmap function will treat the shadow map as if the image were rendered from a light source.

  • teximport

    Imports attributes from texture files.

  • texprintf

    Similar to sprintf, but does expansion of UDIM or UVTILE texture filename expansion.

  • texture

    Computes a filtered sample of the texture map specified.

Transforms and Space

  • dihedral

    Computes the rotation matrix or quaternion which rotates the vector a onto the vector b.

  • fromNDC

    Transforms a position from normal device coordinates to the coordinates in the appropriate space.

  • getspace

    Returns a transform from one space to another.

  • instance

    Creates an instance transform matrix.

  • lookat

    Computes a rotation matrix or angles to orient the z-axis along the vector (to-from) under the transformation.

  • maketransform

    Builds a 3×3 or 4×4 transform matrix.

  • ntransform

    Transforms a normal vector.

  • ow_nspace

    Transforms a normal vector from Object to World space.

  • ow_space

    Transforms a position value from Object to World space.

  • ow_vspace

    Transforms a direction vector from Object to World space.

  • polardecomp

    Computes the polar decomposition of a matrix.

  • ptransform

    Transforms a vector from one space to another.

  • rotate

    Applies a rotation to the given matrix.

  • rotate_x_to

    Rotates a vector by a rotation that would bring the x-axis to a given direction.

  • scale

    Scales the given matrix in three directions simultaneously (X, Y, Z - given by the components of the scale_vector).

  • smoothrotation

    Returns the closest equivalent Euler rotations to a reference rotation.

  • toNDC

    Transforms a position into normal device coordinates.

  • translate

    Translates a matrix by a vector.

  • tw_nspace

    Transforms a normal vector from Texture to World space.

  • tw_space

    Transforms a position value from Texture to World space.

  • tw_vspace

    Transforms a direction vector from Texture to World space.

  • vtransform

    Transforms a directional vector.

  • wo_nspace

    Transforms a normal vector from World to Object space.

  • wo_space

    Transforms a position value from World to Object space.

  • wo_vspace

    Transforms a direction vector from World to Object space.

  • wt_nspace

    Transforms a normal vector from World to Texture space.

  • wt_space

    Transforms a position value from World to Texture space.

  • wt_vspace

    Transforms a direction vector from World to Texture space.

Utility

  • assert_enabled

    Returns 1 if the VEX assertions are enabled (see HOUDINI_VEX_ASSERT) or 0 if assertions are disabled. Used the implement the assert macro.

  • assign

    An efficient way of extracting the components of a vector or matrix into float variables.

  • error

    Reports a custom runtime VEX error.

  • forpoints

  • getcomp

    Extracts a single component of a vector type, matrix type, or array.

  • isbound

    Parameters in VEX can be overridden by geometry attributes (if the attributes exist on the surface being rendered).

  • isvarying

    Check whether a VEX variable is varying or uniform.

  • opend

    Ends a long operation.

  • opstart

    Start a long operation.

  • pack_inttosafefloat

    Reversibly packs an integer into a finite, non-denormal float.

  • print_once

    Prints a message only once, even in a loop.

  • printf

    Prints values to the console which started the VEX program.

  • select

    Returns one of two parameters based on a conditional.

  • set

    Creates a new value based on its arguments, such as creating a vector from its components.

  • setcomp

    Sets a single component of a vector or matrix type, or an item in an array.

  • sleep

    Yields processing for a certain number of milliseconds.

  • swizzle

    Rearranges the components of a vector.

  • unpack_intfromsafefloat

    Reverses the packing of pack_inttosafefloat to get back the original integer.

  • warning

    Reports a custom runtime VEX warning.

volume