# HOUDINI VEX PDF

Hit the little plug icon to the right of the text editor, Houdini scans the vex code, realises you’ve referred to a channel that doesn’t exist yet, and. bookmark_tabs: A collection of code snippets and examples showing syntax and capabilities of VEX language inside SideFX Houdini – jtomori/vex_tutorial. Introduction. For those who tried (or afraid to start) to learn VEX but fail and stop because it was too hard. Here you will learn VEX and some.

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

Copies the value of a geometry attribute into a variable and returns a success flag. Interpolates the value of an attribute at a certain parametric u, v position and copies it into a variable. Returns position derivative on a primitive at a certain parametric u, v position.

Returns one of the set of unique values across all values for an int or string attribute. Returns the set of unique values across all values for an int or string attribute. Interpolates the value of an attribute at certain UV coordinates using a UV attribute.

Returns the albedo percentage of reflected light for a bsdf given the outgoing light direction. Returns an anisotropic housini BSDF, which can scatter light forward or backward.

Returns 1 if the edge specified by the point pair is in the group specified by the string. This function computes the intersection of the specified ray with the geometry in uv space. Returns the linear vertex number of the next vertex sharing a point with a given vertex.

### VEX language reference

Returns the linear vertex number of the previous vertex sharing a point with a given vertex. Returns 1 if the point specified by the point number is in the group specified by the string. Returns 1 if the primitive specified by the primitive number is in the group specified by the string.

Returns 1 if the vertex specified by the vertex number is in the group specified by the string. Returns the point into which the vertex following the destination vertex noudini a half-edge in its primitive is wired.

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

## HoudiniVex

Returns the vertex that precedes the source vertex of a half-edge in its primitive. Finds and returns a half-edge with a given source point or with given source and destination points.

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

Returns the default name of the color plane as it appears in the compositor preferences. Returns the default name of the depth plane as it appears in the compositor preferences. Returns the number of components in the plane named planename in the specified input.

Returns the default name of the luminence plane as it appears in the compositor preferences. Returns the default name of the mask plane as it appears in the compositor preferences. Returns the default name of the normal plane as it appears in the compositor preferences. Returns the number of components in the plane 1 for scalar planes and up to 4 for vector planes. Returns the default name of the point plane as it appears in the compositor preferences. Returns the default name of the velocity plane as it appears in the compositor preferences.

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

Takes the value in the range -1, 1 and shifts it to the corresponding value in a new range. Sends a ray from the position P along the direction specified by the direction D. Returns the derivative of the given value with respect to the 3rd axis for volume rendering. This function returns the closest distance between the point Q and a finite line segment between points P0 and P1. Sets two vectors to the minimum and maximum corners of the bounding box for the geometry.

Returns the relative position of the point given with respect to the bounding box of the geometry. Finds the distance of a point to a group of points along the surface of a geometry.

Once you get a handle to a metaball using metastart and metanext, you can query attributes of the metaball with metaimport. 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. Iterate to the next metaball in the list of metaballs returned by the metastart function. Open a geometry file and return a “handle” for the metaballs of interest, at the position p. There are two forms of Perlin-style noise: Produces the exact same results as the Houdini expression function of the same name.

Generates turbulence matching the output of the HScript turb expression function. Generates a random Poisson variable given the mean to the distribution and a seed. 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. This is the periodic simplex noise. In shading contexts, computes a normal. Returns the value of the point attribute for the metaballs if metaball geometry is specified to i3dgen.

Returns the density of the metaball field if metaball geometry is specified to i3dgen. Returns the distance to the farthest point found in the search performed by pcopen. Imports channel data from a point cloud outside a pciterate or a pcunshaded loop. This function can be used to iterate over all the points which were found in the pcopen query. Changes the current iteration point to a leaf descendant of the current aggregate point.

This function queries the 3D texture map specified and returns the bounding box information of the file. Generates a uniform unit vector2, within maxangle of center, given a uniform number between 0 and 1.

Generates a uniform unit vector, within maxangle of center, given a vector2 of uniform numbers between 0 and 1. Generates a uniform unit vector, given a vector2 of uniform numbers between 0 and 1. Returns an integer, either uniform or weighted, given a uniform number between 0 and 1.

Samples geometry in the scene and returns information from the shaders of surfaces that were sampled. Generates a unit vector, optionally biased, within a hemisphere, given a vector2 of uniform numbers between 0 and 1. Samples the log-normal distribution based on parameters of the underlying normal distribution. Generates a uniform unit vector4, within maxangle of center, given a vector of uniform numbers between 0 and 1.

Generates a uniform unit vector4, given a vector of uniform numbers between 0 and 1. Generates a uniform vector with length sampledisk. Sends rays into the scene and returns information from the shaders of surfaces hit by the rays.

Returns the blurred point position P vector at a fractional time within the motion blur exposure. Evaluates local curvature of primitive grid, using the same curvature evaluation method as Measure SOPs. Returns an approximation to the contribution of the ray to the final pixel color.

### HoudiniVex – cgwiki

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

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

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. Indicats whether houudini shader is being evaulated while doing UV rendering e. Returns the vector representing the reflection of the direction against the normal. Returns the refraction ray given an incoming direction, hourini normalized normal and an index of refraction. Executes the shadow shader for a given light and returns the amount of shadowing as a multiplier of the shaded color.

Formats a string like printf but returns the result as a string instead of printing it. The depthmap functions work noudini an image which was rendered as a z-depth image from mantra. The shadowmap function will treat the shadow map as if the image were rendered from a light source. Computes the rotation matrix or quaternion which rotates the vector vec onto the vector b. Transforms a position from normal device coordinates to the coordinates in the appropriate space.

Computes a rotation matrix or angles to orient the z-axis along the vector to-from under the transformation. Used the implement the assert macro. An efficient way of extracting the components of a vector or matrix into float variables. Parameters in VEX can be overridden by geometry attributes if the attributes exist on the surface being rendered. Creates a new value based on its arguments, such as creating a vector from its components.

Loops and flow control. Overview of how to use the VEX language compiler vcc and its pre-processor and pragma statements. Working with geometry groups in VEX. Using assertions in VEX.