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VEX functions

See VEX contexts to learn about the different contexts (such as surface shaders or displacement shaders) in which the various functions and statements are available.

Subtopics

Du vex function
Takes the derivative of the given value with respect to U.
Dv vex function
Takes the derivative of the given value with respect to V.
abs vex function
Returns the absolute value of the argument.
acos vex function
Returns the arc-cosine of the argument.
addattribute vex function
Adds or changes a point attribute.
addgroup vex function
Adds the particle specified by point_number to the group specified.
addvariablename vex function
Adds the mapping of the attribute aname to the local variable vname.
alphaname vex function
Returns the default name of the alpha plane (as it appears in the compositor preferences).
ambient vex function
Returns the color of ambient light in the scene.
anoise vex function
These functions are similar to the Worley noise functions listed above.
area vex function
Computes the shading area of the variable.
ashikhmin vex function
asin vex function
Returns the arc-sine of the argument.
assign vex function
An efficient way of extracting the components of a vector, vector4, matrix3 or matrix to float variables.
atan vex function
Returns the arc-tangent of the argument.
atan2 vex function
Returns the arc-tangent of y/x.
atof vex function
Converts a string to a float.
atoi vex function
Converts a string to an integer.
atten vex function
Computes attenuated falloff.
avg vex function
Returns the average of the vector’s 3 components
binput vex function
binput returns bilinear sampled input.
blinn vex function
phong, blinn, and specular return the illumination for specular highlights using different lighting models.
blinnBRDF vex function
bumpmap vex function
Bump maps will return the color gradient of the image in the du/dv parameters.
bumpmapA vex function
bumpmapB vex function
bumpmapG vex function
bumpmapL vex function
bumpmapR vex function
bumpname vex function
Returns the default name of the bump plane (as it appears in the compositor preferences).
ceil vex function
Returns the smallest integer greater than or equal to the argument
ch vex function
Evaluates a channel (or parameter) and return its value.
chend vex function
Returns the end sample of the input specified.
chendf vex function
Returns the frame corresponding to the last sample of the input specified.
chendt vex function
Returns the time corresponding to the last sample of the input specified.
chinput vex function
Returns the value of a channel at the specified sample in an input.
chname vex function
Returns the channel name of the indexed plane.
chnumchan vex function
Returns the number of channels in the input specified.
chrate vex function
Returns the sample rate of the input specified.
chstart vex function
Returns the start sample of the input specified.
chstartf vex function
Returns the frame corresponding to the first sample of the input specified.
chstartt vex function
Returns the time corresponding to the first sample of the input specified.
cinput vex function
cinput returns point sampled input.
ckspline vex function
Computes a Catmull-Rom (Cardinal) spline between the key points specified.
clamp vex function
Returns value clamped between min and max.
clip vex function
clip the line segment between p0 and p1.
colormap vex function
There are various forms for looking up a color from a disk image.
colorname vex function
Returns the default name of the color plane (as it appears in the compositor preferences).
computenormal vex function
In the POP and SOP contexts, sets how/whether to recompute normals. In the shading contexts, computes normals.
concat vex function
Concatenate all the strings specified to form a single string.
cone vex function
cos vex function
Returns the cosine of the argument.
cosh vex function
Returns the hyperbolic cosine of the argument.
cracktransform vex function
Depending on the value of c, returns the translate (c=0), rotate (c=1), or scale (c=2) component of the transform (xform).
cross vex function
Returns the cross product between the two vectors
cspline vex function
Computes a Catmull-Rom (Cardinal) spline between the key points specified.
degrees vex function
Returns the argument from radians into degrees
depthmap vex function
The depthmap functions work on an image which was rendered as a z-depth image from mantra.
depthname vex function
Returns the default name of the depth plane (as it appears in the compositor preferences).
determinant vex function
computes the determinant of the matrix
diffuse vex function
Returns the diffuse (Lambertian) illumination given the normalized surface normal.
diffuseBRDF vex function
dihedral vex function
computes the rotation matrix which rotates the vector a onto the vector b.
dimport vex function
Imports a variable from the displacement shader for the surface.
distance vex function
Returns the distance between the two 3 or 4 dimensional point arguments.
distance2 vex function
Returns the squared distance between the two 3 or 4 dimensional point arguments.
dot vex function
Returns the dot product between the arguments.
environment vex function
Returns the color of the environment texture.
exp vex function
Returns the exponential function of the argument.
fastshadow vex function
Sends a ray from the position P along the direction specified by the direction D.
filtershadow vex function
Sends a ray from the position P along direction D.
filterstep vex function
Returns the anti-aliased weight of the step function.
finput vex function
finput returns fully filtered pixel input.
fit vex function
Takes the value in the range (omin, omax) and shifts it to the corresponding value in the new range (nmin, nmax).
floor vex function
Returns the largest integer less than or equal to the argument
fntransform vex function
forpoint vex function
frac vex function
Returns the fractional component of the floating point number.
fresnel vex function
Computes the fresnel reflection/refraction contributions given an incoming vector, surface normal (both normalized), and an index of refraction (eta).
fromNDC vex function
Transforms a position from normal device coordinates to the coordinates in the appropriate space.
frontface vex function
If dot(I, Nref) is less than zero, N will be negated.
ftransform vex function
fvtransform vex function
gather vex function
Sends rays into the scene and returns information from the shaders of surfaces hit by the rays.
getbbox vex function
Sets two vectors to the minimum and maximum corners of the bounding box for the entire geometry.
getblurP vex function
Returns the blurred point position (P) vector at a fractional time between frames.
getbounds vex function
Returns the bounding box of the geometry specified by the filename.
getcomp vex function
Extract a single component of a vector, vector4, matrix3 or matrix.
getglobalraylevel vex function
Returns the depth of the ray tree for computing global illumination.
getlightname vex function
Returns the name of the current light when called from within an illuminance loop.
getneighbour vex function
Returns the point index of the neighbour of the point.
getneighbourcount vex function
Returns the number of points that are connected to the specified point.
getobjectname vex function
Returns the name of the current “object” whose shader is being run.
getraylevel vex function
Returns the depth of the ray tree for the current shading.
getrayweight vex function
Returns an approximation to the contribution of the ray to the final pixel color.
gradient3d vex function
Returns the gradient of a single channel texture image at the position specified by P.
hasplane vex function
Returns 1 if the plane specified by the parameter exists in this COP.
hscript_noise vex function
hscript_noise, hscript_turb, hscript_snoise, and hscript_sturb mimic the Houdini expression functions noise(), snoise(), turb(), and sturb().
hscript_rand vex function
Produces the exact same results as the Houdini expression function of the same name.
hscript_snoise vex function
hscript_sturb vex function
hscript_turb vex function
hsvtorgb vex function
Convert HSV color space into RGB color space.
iaspect vex function
Returns the aspect ratio of the specified input.
ichname vex function
Returns the channel name of the indexed plane of the given input (e.
ident vex function
computes identity matrices
iend vex function
Returns the last frame of the specified input.
iendtime vex function
Returns the end time of the specified input.
ihasplane vex function
Returns 1 if the specified input has a plane named 'planename'.
illuminance vex function
Loops through all light sources in the scene, calling the light shader for each light source to set the Cl and L global variables.
import vex function
Imports attribute data from the SOP or POP connected to the specified input.
ingroup vex function
Returns 1 if the particle specified by the point number is in the group specified by the string.
int vex function
if the argument is negative, this returns ceil(x), otherwise it returns floor(x).
integrate3d vex function
This function will “integrate” the 3d image along the line specified by p0 and p1.
integrate3dClip vex function
The integrate3dClip function integrates along the ray described by p0 and p1 where “interesting” things start happening in a given I3D texture.
intersect vex function
This function computes the intersection of the specified ray with the geometry.
intersect3d vex function
This function intersects a ray (with it’s origin at p0 and extending to p1), against a 3d texture image.
inumplanes vex function
Returns the number of planes in the given input.
invert vex function
inverts the matrix.
iplaneindex vex function
Returns the index of the plane named 'planename' in the specified input.
iplanename vex function
Returns the name of the plane specified by the planeindex of the given input (e.
iplanesize vex function
Returns the number of components in the plane named 'planename' in the specified input.
irate vex function
Returns the frame rate of the specified input.
irradiance vex function
Computes irradiance (global illumination) at the point P with the normal N.
isbound vex function
Parameters in VEX can be overridden by geometry attributes (if the attributes exist on the surface being rendered).
isconnected vex function
Returns 1 if input_number is connected, or 0 if the input is not connected.
isfogray vex function
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.
isframes vex function
Returns 1 if the Vex CHOP’s Unit Menu is currently set to 'frames', 0 otherwise.
issamples vex function
Returns 1 if the Vex CHOP’s Unit Menu is currently set to 'samples', 0 otherwise.
isseconds vex function
Returns 1 if the Vex CHOP’s Unit Menu is currently set to 'seconds', 0 otherwise.
isshadowray vex function
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.
istart vex function
Returns the starting frame of the specified input.
istarttime vex function
Returns the start time of the specified input.
ixres vex function
Returns the X resolution of the specified input.
iyres vex function
Returns the Y resolution of the specified input.
kspline vex function
Returns an interpolated value along a spline curve.
length vex function
Returns the length of the vector or vector4.
length2 vex function
Returns the squared distance of the vector or vector4.
lerp vex function
Performs bilinear interpolation between the values.
limport vex function
Imports a variable from the light shader for the surface.
lkspline vex function
Computes a linear spline between the key points.
lntransform vex function
log vex function
Returns the natural logarithm of the argument
log10 vex function
Returns the logarithm (base 10) of the argument
lookat vex function
computes a rotation matrix to orient the z-axis along the vector (to-from) under the transformation.
lspline vex function
Computes a linear spline between the key points.
ltransform vex function
luminance vex function
Compute the luminance of the RGB color specified by the parameters
lumname vex function
Returns the default name of the luminence plane (as it appears in the compositor preferences).
lvtransform vex function
maketransform vex function
Builds a 3×3 or 4×4 transform matrix.
maskname vex function
Returns the default name of the mask plane (as it appears in the compositor preferences).
match vex function
This function returns 1 if the subject matches the pattern specified, or 0 if the subject doesn’t match.
matchvex_blinn vex function
matchvex_specular vex function
mattrib vex function
Returns the value of the point attribute for the metaballs if metaball geometry is specified to i3dgen.
max vex function
mdensity vex function
Returns the density of the metaball field if metaball geometry is specified to i3dgen.
metaimport vex function
Once you get a handle to a metaball using metastart and metanext, you can query attributes of the metaball with metaimport.
metamarch vex function
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 vex function
metastart vex function
Open a geometry file and return a “handle” for the metaballs of interest, at the position p.
metaweight vex function
Returns the metaweight of the geometry at position p.
min vex function
mspace vex function
Transforms the position specified into the “local” space of the metaball.
newgroup vex function
Creates a new group in which to put particles.
ninput vex function
Reads a pixel and its eight neighbors into a 3×3 matrix.
noise vex function
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.
normalize vex function
Returns the normalized vector
normalname vex function
Returns the default name of the normal plane (as it appears in the compositor preferences).
npoints vex function
nprimitives vex function
Returns the number of primitives in the geometry file.
nrandom vex function
The nrandom() functions are non-deterministic random number generators for VEX.
ntransform vex function
See ptransform.
occlusion vex function
Computes ambient occlusion.
onoise vex function
These functions are similar to wnoise and vnoise.
ontransform vex function
optransform vex function
Returns the transform associated with an OP.
otransform vex function
otransform, ltransform, ftransform, ontransform, lntransform, fntransform, ovtransform, lvtransform, and fvtransform query the scene for a geometry object, light or fog object of the given name.
ovtransform vex function
ow_nspace vex function
Transforms a normal vector from Object to World space.
ow_space vex function
Transforms a position value from Object to World space.
ow_vspace vex function
Transforms a direction vector from Object to World space.
pathtrace vex function
pcclose vex function
This function closes the handle associated with a pcopen function.
pcexport vex function
Writes data to a point cloud inside a pciterate or a pcunshaded loop.
pcfarthest vex function
Returns the distance to the farthest point found in the search performed by pcopen.
pcfilter vex function
Filters the points found by pcopen using a simple reconstruction filter.
pcimport vex function
Imports channel data from a point cloud inside a pciterate or a pcunshaded loop.
pciterate vex function
This function can be used to iterate over all the points which were found in the pcopen query.
pcopen vex function
Returns a handle to a point cloud file.
pcunshaded vex function
Iterate over all of the points of a read-write channel which haven’t had any data written to the channel yet.
pcwrite vex function
Writes data to a point cloud file.
phong vex function
phong, blinn, and specular return the illumination for specular highlights using different lighting models.
phongBRDF vex function
phonglobe vex function
photon_diffuse vex function
Generates a new diffuse photon path randomly distributed over the hemisphere defined by P and N, with energy Cl.
photon_reflect vex function
Generates a new specular photon path defined by the ray starting at P and travelling along R (the reflection direction) with energy Cl.
photon_store vex function
Stores a photon in the appropriate maps.
photon_switch vex function
Takes three arguments which represent the probabilities for each of the reflective paths.
photon_transmit vex function
Generates a new transmission photon path defined by the ray starting at P and traveling along R (the reflection direction) with energy Cl.
photonmap vex function
The photonmap function will evaluate a photon map and return the resulting color information.
planeindex vex function
Returns the index of the plane specified by the parameter, starting at zero.
planename vex function
Returns the name of the plane specified by the index (e.
planesize vex function
Returns the number of components in the plane (1 for scalar planes and up to 4 for vector planes).
pnoise vex function
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.
pointname vex function
Returns the default name of the point plane (as it appears in the compositor preferences).
pow vex function
Raises the first argument to the power of the second argument
prim_attribute vex function
Evaluates the attribute string att for primitive pn at the parametric location u, v.
prim_normal vex function
Returns the normal of the primitive (prim_number) at parametric location u, v.
printf vex function
Prints values to the console which started the VEX program.
ptlined vex function
This function returns the closest distance between the point Q and a finite line segment between points P0 and P1.
ptransform vex function
Transforms a vector from one space to another.
qconvert vex function
Converts a quaternion represented by a vector4 to a matrix3 representation.
qmultiply vex function
Multiplies two quaternions and returns the result.
quaternion vex function
Creates a vector4 representing a quaternion.
radians vex function
Converts the argument from degrees into radians
random vex function
generate a random number based on the position in N dimensional space (where N is 1 to 4 dimensions).
rawbumpmap vex function
rawbumpmapA vex function
rawbumpmapB vex function
rawbumpmapG vex function
rawbumpmapL vex function
rawbumpmapR vex function
rawcolormap vex function
rayhittest vex function
Sends a ray from the position P along the direction D.
rayimport vex function
Imports a value sent by a shader in a gather loop.
reflect vex function
Returns the vector representing the reflection of the direction against the normal.
reflectlight vex function
Computes the amount of reflected light which hits the surface.
refract vex function
Returns the refraction ray given an incoming direction, the normalized normal and an index of refraction.
refractlight vex function
Computes the illumination of surfaces refracted by the current surface.
relbbox vex function
Returns the relative position of the point given with respect to the bounding box of the entire geometry.
removegroup vex function
Removes the particle specified by point_number from the group specified.
renderstate vex function
Queries the renderer for a named property.
rgbtohsv vex function
Convert RGB color space to HSV color space.
rint vex function
Rounds the number to the closest integer.
rotate vex function
applies a rotation to the given matrix.
scale vex function
scales the given matrix in three directions simultaneously (X, Y, Z - given by the components of the scale_vector).
set vex function
These two functions provide a very efficient way of creating a vector/vector4.
setcomp vex function
These functions set a single component of a vector, vector4, matrix3 or matrix.
shadow vex function
Calls shadow shaders for the current light source.
shadowmap vex function
The shadowmap function will treat the shadow map as if the image were rendered from a light source.
shimport vex function
Imports a variable from the shadow shader for the surface.
simport vex function
Imports a variable sent by a surface shader in an illuminance loop.
sin vex function
Returns the sine of the argument
sinh vex function
Returns the hyperbolic sine of the argument
sleep vex function
Yields processing for a certain number of milliseconds.
slerp vex function
Quaternion blend between q1 and q2 based on the bias.
smooth vex function
Computes a number between zero and one.
snoise vex function
These functions are similar to wnoise.
specular vex function
phong, blinn, and specular return the illumination for specular highlights using different lighting models.
specularBRDF vex function
specularBRDF, phongBRDF, blinnBRDF, and diffuseBRDF return the computed BRDFs for the different lighting models used in VEX shading.
spline vex function
Returns an interpolated value along a polyline or spline curve.
sprintf vex function
Formats a string like printf but returns the result as a string instead of printing it.
sqrt vex function
Returns the square root of the argument
strlen vex function
Returns the length of the string.
tan vex function
Returns the trigonometric tangent of the argument
tanh vex function
Returns the hyperbolic tangent of the argument
teximport vex function
Imports attributes from texture files.
texture vex function
Computes a filtered sample of the texture map specified.
texture3d vex function
Returns the value of the 3d image at the position specified by P.
texture3dBox vex function
This function queries the 3D texture map specified and returns the bounding box information of the file.
toNDC vex function
Transforms a position into normal device coordinates.
trace vex function
Sends a ray from P along the normalized vector D.
translate vex function
translates the given matrix
transpose vex function
transposes the given matrix
tw_nspace vex function
Transforms a normal vector from Texture to World space.
tw_space vex function
Transforms a position value from Texture to World space.
tw_vspace vex function
Transforms a direction vector from Texture to World space.
velocityname vex function
Returns the default name of the velocity plane (as it appears in the compositor preferences).
vnoise vex function
Voronoi noise gives almost identical results to the Worley noise functions.
volumegradient vex function
Calculates the volume primitive’s gradient.