HOM
hou
Module containing all the sub-modules, classes, and functions to access Houdini.
Subtopics
Assets
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Represents the definition of a houdini digital asset (HDA).
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User-defined Python module containing functions, classes, and constants that are stored with and accessed from a digital asset.
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Stores miscellaneous options about a houdini digital asset (HDA).
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Represents a “section” of data stored along with a digital asset.
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Module containing functions related to Houdini Digital Assets.
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Enumeration of digital asset license permission levels.
Channels
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Class representing a CHOP node.
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Evaluate a Bezier interpolation spline for an animated parameter using the left keyframe’s outgoing value, tangent, and acceleration and the right keyframe’s incoming value, tangent, and acceleration.
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Evaluate an animation function for an animated parameter. The return value is always the left keyframe’s outgoing value.
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Smooth curve between the left keyframe’s outgoing slope and the right’s incoming slope.
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Repeats the motion between two frames, lining up the first repeated value with the left keyframe’s value.
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Repeats the motion between two times, lining up the repeated values with the left keyframe’s value.
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Interpolates between the left keyframe’s outgoing value and the right keyframe’s incoming value.
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Interpolates between the left keyframe’s outgoing value and the right keyframe’s incoming value.
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Interpolates between the values of two keyframes.
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Interpolates between the left keyframe’s outgoing value and the right keyframe’s incoming value.
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Interpolates between the values of two keyframes.
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Interpolates between the values of two keyframes.
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Linearly interpolates between the left keyframe’s outgoing value and the right keyframe’s incoming value.
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Creates a smooth curve between the left keyframe’s incoming slope and the right keyframe’s outgoing slope.
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Creates a straight line from the left keyframe’s incoming value, matching the left keyframe’s incoming slope.
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Creates a straight line from the right keyframe’s outgoing value, matching the right keyframe’s outgoing slope.
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Linearly interpolates between keyframes using quaternions.
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Evaluate an interpolation function for an animated parameter that gives a smooth curve between the left keyframe’s outgoing value and the right keyframe’s incoming value, using the left’s outgoing slope and acceleration and the right’s incoming slope and acceleration.
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Repeats the motion between two times.
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Repeats the motion between two times.
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Fits a spline through consecutive keyframe values.
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Matches the incoming and outgoing values and slopes.
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Matches the left keyframe’s incoming slope.
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Matches the right keyframe’s outgoing slope.
Cooking
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Return Houdini’s cook update mode (Auto Update/On Mouse Up/Manual) that is displayed in the status bar.
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Enumeration of interface update modes.
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Return Houdini’s cook update mode (Auto Update/On Mouse Up/Manual) that is displayed in the status bar.
Dynamics
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A piece of data stored inside a DOP network’s simulation.
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Describes the type of data in a DOP object.
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Represents a dynamics (DOP) network node.
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Represents a dynamics node.
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A type of DOP data that contains an object in the simulation.
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A table of values stored inside a DopData.
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A type of DOP data that stores which DOP objects affect one another.
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A dynamics simulation contained inside a DOP network node.
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DOP related functions.
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Enumeration of field types.
Exceptions
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Base class for all exceptions in the hou module.
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Exception that is raised when you try to modify geometry from outside of a Python SOP.
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Exception that is raised when you try to set a node’s input to something invalid.
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Exception that is raised when you try to call a method on a Node that isn’t supported by that type of node.
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Exception that is raised when you pass a sequence of the wrong length to a function.
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Exception class for when loading a hip file in Houdini generates warnings.
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Exception class for when an operation attempted to use a feature that is not available. This class is a subclass of .
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Exception class for when you use a stale variable to attempt to access something that was deleted in Houdini. This class is a subclass of .
General
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This class is the base class for an enumeration value. It cannot be instanced and is not meant to be used directly by the user.
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The variable() function returns a variable by name. The Variable class represents Houdini variables.
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Returns whether Houdini is in the process of exiting. This function is called internally by the interactive Houdini Python shell.
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Allow (or disallow) an environment variable to overwrite the value of a global variable saved in a hip file.
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Compares two numbers and returns True if they are almost equal in terms of how far apart they are when represented as floating point numbers.
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Appends the given source code to the hou.session module. The appended code is made available immediately. You do not have to re-import hou.session.
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Returns the application’s compilation date.
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Returns the application name.
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Returns the application’s version number as a tuple of integers – (major_version, minor_version, build_version).
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Returns the application’s version number as a string.
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Functions related to playing audio using Houdini’s playbar.
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Exits Houdini, returning the exit code to the operating system. If suppress_save_prompt is false, this function asks the user if he/she wants to save. If the user presses “Cancel”, the exit will be canceled and the next statement will execute.
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Houdini and 3D related math functions.
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Return whether the application is an apprentice (non-commercial) version.
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Return the category of license (Commercial, Apprentice, ApprenticeHD, etc.) in use.
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Release the currently held Houdini license.
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This module is used to define custom classes, functions and variables that can be called from within the current Houdini session. The contents of this module are saved into the .hip file.
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Returns the contents of the hou.session module.
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Sets the contents of the hou.session module. The new contents is made available immediately. You do not have to re-import hou.session.
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Enumeration of license category values.
Geometry
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Enumeration of attribute data types.
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This class stores information about a Geometry attribute.
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A Face is a kind of geometry primitive (Prim object) that contains a sequence of vertices (Vertex objects). How these vertices are used depends on the type of face; polygons, for example, use the vertices to define the edges of the polygon, while NURBS curves use them as control points.
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A Geometry object contains the points and primitives that define a 3D geometric shape. For example, each SOP node in Houdini generates a single Geometry object.
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Each Point object resides inside a Geometry object and stores a 3D position. Points may be shared between primitives (such as polygons), and the set of points and primitives describes a 3D shape.
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A Polygon is a kind of Face whose vertices are connected via straight lines.
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Each Prim resides inside a Geometry object and stores some sort of 3D geometric primitive, like a polygon, a NURBS curve, or a volume. Each primitive usually contains a set of Vertex objects, each of which references a Point object.
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A Quadric is a kind of geometry primitive (Prim object) that represents a 3-dimensional surface defined by a quadratic polynomial equation (e.g. a sphere or tube).
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Represents a surface node.
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A Surface is a kind of geometry primitive (Prim object) that contains a two dimensional grid of vertices (Vertex objects). How these vertices are used depends on the type of surface: meshes, for example, use the vertices to define a quadrilateral mesh, while NURBS surfaces use them as control points.
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Existing inside a Geometry object, a Vertex object is contained in exactly one Prim, and references exactly one Point.
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A Volume is a kind geometry primitive (Prim object) storing a three dimensional array of voxels.
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Enumeration of geometry attribute types.
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Enumeration of geometry component types.
IO
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Search the houdini path for the specified directory, returning a tuple of all the matches. The directory name specified should be relative to the houdini directory.
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Search the houdini path for a specified directory, returning the first match found. The directory name specified should be relative to the houdini directory.
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Search the houdini path for a specified file, returning the first match found. The filename specified should be relative to the houdini directory.
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Search the houdini path for the specified file, returning a tuple of all the matches. The filename specified should be relative to the houdini directory.
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Return the path to the Houdini directory in your $HOME directory.
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Return the contents of the Houdini path as a tuple of strings.
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Read a file, returning the contents in a string. Supports regular files, opdef: and oplib: paths, and http URLs.
Images
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Represents a compositing node.
Keyframes
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Abstract base class for all keyframe class.
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Class representing the default keyframe type, a numerical keyframe.
Materials
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The base class for all SHOP nodes in Houdini. An instance of this class corresponds to exactly one instance of a node in Houdini.
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Enumeration of SHOP shader types.
Node Organization
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Represents a network box.
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A named set of nodes whose contents can be from different networks. A bundle’s contents may be fixed or may be determined from a pattern, and the contents may be filtered by node type.
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Represents a node group.
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Represents a sticky note.
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Create a new node bundle with the specified name.
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Given a node bundle name, return the corresponding NodeBundle object, or None if there is not one with that name.
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Return a tuple containing all the node bundles in the current session.
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Enumeration of available node type filters.
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Return a tuple containing all the node bundles that are selected in the bundle list pane.
Node type categories
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Represents a category of node types, such as surface nodes (SOPs) or particle nodes (POPs).
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Return the NodeTypeCategory instance for Houdini channel container (chopnet) nodes.
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Return the NodeTypeCategory instance for Houdini channel (chop) nodes.
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Return the NodeTypeCategory instance for Houdini composite container (copnet) nodes.
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Return the NodeTypeCategory instance for Houdini composite (cop) nodes.
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Return the NodeTypeCategory instance for Houdini dynamic (dop) nodes.
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Return the NodeTypeCategory instance for Houdini manager nodes. The manager nodes are /obj, /out, /part, /ch, /shop, /img, and /vex.
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Return a dictionary where the keys are the category names (e.g. “Object”, “Sop”) and the values are hou.NodeTypeCategory objects.
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Return the NodeTypeCategory instance for Houdini object nodes. For example, if /obj/model is an object then hou.node(“/obj/model”).type().category() is hou.objectNodeTypeCategory().
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Return the NodeTypeCategory instance for Houdini particle container (popnet) nodes.
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Return the NodeTypeCategory instance for Houdini particle (pop) nodes.
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Return the NodeTypeCategory instance for Houdini root (/) node. There is only one instance of the root node, and it has its own node type category.
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Return the NodeTypeCategory instance for Houdini output (rop) nodes.
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Return the NodeTypeCategory object corresponding to shader (SHOP) nodes.
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Return the NodeTypeCategory instance for Houdini geometry (sop) nodes.
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Return the NodeTypeCategory instance for Houdini vex builder container (vopnet) nodes.
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Return the NodeTypeCategory instance for Houdini vex builder (vop) nodes.
Nodes
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The base class for all nodes in Houdini (objects, SOPs, COPs, etc.) An instance of this class corresponds to exactly one instance of a node in Houdini.
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Represents a connection (wire) between two Nodes.
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A NodeType specifies the information common to all instances of a type of node, such as the parameter set, algorithm, minimum number of inputs, etc. For example, the geometry object and subdivide SOP are node types. /obj/geo1 and /obj/geo2, on the other hand, are Nodes that are instances of the geometry object node type.
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Represents a particle node.
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This kind of NodeType contains extra attributes specific to SOP nodes.
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A node-like square that appears inside subnets and corresponds to the node wired into the subnet.
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Change the current node. Houdini has one current node, analogous to a current directory in a file system. If a relative path is given, it is relative to the node returned by hou.pwd().
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Copy all given nodes to a new place in node hierarchy.
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Move all given nodes to a new place in node hierarchy.
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Given a path string, return a Node object. Return None if the path does not refer to a node.
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Given a node type category object and a name, return the corresponding NodeType object. Return None if there is no such type with that name.
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Enumeration of node type sources.
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Enumeration of permission flag combinations.
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If called from an evaluating parm, return the node containing the parm. Otherwise, return Houdini’s global current node. You can change this current node with hou.cd
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Return the root node (i.e. /).
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Return a list of all selected nodes.
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Make the given node Houdini’s current node. This function is equivalent to hou.cd(node.path()).
Objects
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An instance of this class corresponds to exactly one instance of an object node in Houdini.
Parameter templates
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Describes a button parameter.
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Describes a set of folders.
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Describes a label parameter.
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Describes a menu parameter.
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Parameter template for a ramp parameter.
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Template for a separator parameter. Separators are just lines between parameters.
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Enumeration of parameter data types.
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Enumeration of available looks for a parameter
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Enumeration of available naming schemes for a parameter.
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Enumeration of parameter template types.
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Enumeration of string parameter types.
Parameters
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A parameter in a node. Each parameter has a unique name within its node and exists inside a parameter tuple.
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A tuple of one or more node parameters. Each parameter tuple has a unique name within its node.
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The same as evalParm(). Provided for backward compatibility.
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Evaluate a parameter that references a node, and return the absolute path to the node.
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Evaluate a parameter, given either an absolute or a relative path to it. Relative path searches are done from the node returned by . This function is a shortcut for hou.parm(path).eval().
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Evaluate a parameter, given either an absolute or a relative path to it. Relative path searches are done from the node returned by . This function is a shortcut for hou.parmTuple(path).eval().
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Enumeration of available expression languages.
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Enumeration of file types.
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Return the value of a node’s local variable. Call this function from expressions inside node parameters.
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Given a path string, return a Parm object. Return None if the path does not refer to a parameter.
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Given a path string, return a ParmTuple object. Return None if the path does not refer to a parameter tuple.
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Enumeration of available script languages.
Rendering
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Represents a render output node.
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Enumeration of dependency rendering methods.
Scripting
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Used internally by Houdini to preload icons for speed.
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This function is used internally by the Houdini Python shell for argument auto-completion on functions of the hou module.
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Evaluates the given string expression and returns the result.
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Evaluates the given string expression at a certain frame and returns the result.
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Return the globals dictionary used by the parameter expression evaluation namespace.
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Executes the given hscript command and returns a 2-tuple of strings where the first string contains the regular output of the executed command and the second string contains the error output. You can specify multiple commands by using ';' or the newline character as the separator.
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Return the text help of an hscript command. This function is used to help re-implement hscript commands in Python.
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Deprecated: Use expandString.
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Evaluate an Hscript expression.
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Evaluate an Hscript expression as a float.
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Evaluate an Hscript expression as a vector.
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Evaluate an Hscript expression as a float.
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Evaluate an Hscript expression as a vector.
Shelf
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Represents the shelf area at the top of the screen, within which shelf sets and shelf tabs exist.
Timeline
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Return the number of frames per second.
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Return the playbar’s current frame. Note that Houdini can be on a fractional frame if fractional frames are enabled.
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Convert from a given frame value to a time value.
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Return the playbar’s current frame, rounded to the nearest integer.
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Set the number of frames per second.
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Set the playbar’s current frame. Note that the frame may be a fractional value.
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Set the playbar’s time.
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Return the playbar’s current time, in seconds of playback.
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Convert from a given time value to a frame value, rounding the result to a integer if it is close to an integer.
UI
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Class representing a Houdini desktop (a pane layout).
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A floating window that contains one or more panes.
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Class representing a help browser pane tab. Provides methods for controlling the help browser.
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An interactive preview render (IPR) window.
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A rectangular area of the desktop that contains one or more pane tabs.
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One of the tabs inside a desktop pane.
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Enumeration of possible read/write modes for the file chooser.
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Return whether or not the hou.ui module is available.
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Enumeration of possible pane link values.
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Enumeration of pane tab types.
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Enumeration of dialog message severities.
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Module containing user interface related functions.
Utility
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An axis-aligned 3D rectangular region.
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A 3×3 matrix of floating point values.
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A 4×4 matrix of floating point values.
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A representation of a 3D rotation (or orientation). You can smoothly interpolate between two rotation values by interpolating between two quaternions.
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A Ramp represents a function that yields either floating point values or colors. You can evaluate this function between 0.0 and 1.0, and the function’s shape is determined by a sequence of values at key positions between 0.0 and 1.0.
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This kind of NodeType contains extra attributes specific to SHOP nodes.
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A sequence of 2 floating point values, with associated mathematical operations.
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A sequence of 3 floating point values, with associated mathematical operations.
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A sequence of 4 floating point values, with associated mathematical operations.
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Enumeration of color types.
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Enumeration of ramp interpolation types.
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Enumeration of ramp types.
VEX
Viewer
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A class representing a context viewer pane tab.
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Describes how Houdini should prompt the user to choose geometry in the viewport when creating a new SOP node instance.
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Enumeration of component types.
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Enumeration of connectivity types.
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Enumeration of scene viewer viewport types.
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Enumeration of spaces.
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Enumeration of viewer shading modes.
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Enumeration of snapping modes.