Houdini 20.0 Nodes Render nodes

Wedge render node

Re-renders the same ROP multiple times with different settings

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The Wedge ROP will render the specified ROP multiple times. Each time it will vary some parameters in the .hip file. This is useful for exploring how changing parameters will change the look for expensive functions.

The WEDGE variable will be set to a string that describes the current set of parameters. Using this in filenames output can ensure each wedge doesn’t conflict with the other wedges. Alternatively, if one is wedging to MPlay, the individual wedges will render together. The output file could be set to filename_$WEDGE_$F.pic to ensure each wedge gets its own image sequence.

If wedging images, you can also use the hwatermark program to stamp the images with the wedge name. Setting the Post Frame Script to

unix hwatermark -x 4 10 -m \"Wedge: $WEDGENUM\" `chs("vm_picture")` `chs("vm_picture")` $HFS/houdini/fonts/Helvetica-Bold.pfa 24

The WEDGENUM variable will be set to the currently processed wedge number. This ranges from 0 to one less than the number of wedges. If you render a specific wedge with the Wedge Range, WEDGENUM will be set to that wedge number.


Render Wedges

Runs the specified render operation once for each wedge.


This prefix is added at the front of the WEDGE variable. This can be used to separate different sets of wedges.

Wedge Range

All Wedges will cause every computed wedge to be rendered at once. Alternatively, one specific wedge can be rendered. The latter is useful if manually splitting up the wedges across machines, which may be necessary for simulations.

Output Driver

Which ROP will be run for each wedge. The ROP should have a parameter called “take” for take based wedging to work. If it outputs to a file, the filename should have $WEDGE in it to avoid writing the same file twice.

Wait for Render to Complete

Sets the Wait for Render to Complete temporarily on the Output Driver. This avoids all the wedges being started simultaneously, which can inconvenience a single-user machine. However, by not blocking, you can return control to Houdini quickly while waiting for the renders to run in background.

Wedge Method

Controls how the scene is varied.

By Channels

Each of the Wedge Parameters is varied according to its number of steps and range and applied to its specified channel. All combinations of the parameters are then wedged. The total number of wedges is the product of all of the step values.

By Take

One wedge is performed for each immediate child of the given parent take. The output driver’s take parameter is set to each child take’s value.

Parent Take

In By Take wedging, this is the name of the parent take. Only immediate children of this take are used for wedges.

Random Samples

Instead of uniformly sampling each range, a random value will be picked inside the range for each sample.

Number of Samples

Determines how many wedges will be run when in random sampling mode.

Random Seed

The seed used for generating the random samples. Changing this will create a different set of random samples.

Wedge Parameters

The number of parameters to use in By Channel wedging. Each parameter is a single float value which is divided uniformly across a given interval.


The English name of the channel. This is added to the WEDGE variable. If blank, the channel name is used.


The channel path to vary. This is a full channel path, a path to a node followed by the name of a channel. Note that it is not a parameter path: /obj/geo1/tx is legal but /obj/geo1/t is not.


The minimum and maximum values that the channel will vary over.

Number of Steps

The number of steps that the range will be broken into. Ignored if random sampling is performed.


rop_example_wedge Example for Wedge render node

This example shows how to setup the Wedge ROP to automatically create a bunch of variants of a network.

Render nodes

  • Agent

    This output operator is used to write agent definition files.

  • Alembic

    Exports the scene to an Alembic archive. Alembic is a common exchange format for moving geometry and animation between different 3D software packages.

  • Archive Generator

    Generates disk-based archives which can be used by either mantra or RIB renderers.

  • Bake Animation

    Bakes animation from object transforms and CHOP overrides.

  • Bake Texture

    Generates a texture map from one or more objects' rendered appearance.

  • Batch

    Renders the input ROP in a single batch job.

  • Channel

    The Channel output operator generates clip files from a particular CHOP.

  • Composite

    Renders images from a compositing network.

  • DSM Merge

    Merges two or more deep shadow/camera map files.

  • Dem Bones Skinning Converter

    Converts any non-changing topology deforming mesh sequence into a bone-based animation.

  • Dynamics

    Saves the state of a DOP network simulation into files.

  • Fetch

    Makes a dependency link to a ROP in a different network.

  • Filmbox FBX

    Exports entire scenes to FBX files.

  • Filmbox FBX Animation

    Export animation from geometry-based skeleton to an FBX file.

  • Filmbox FBX Character

    Export a skinned character with geometry-based skeleton to an FBX file.

  • Frame Container

    Prevents frame dependency changes in the contained nodes from affecting its inputs.

  • Frame Depedency

    Allows an output frame to depend on one or more input frames.

  • GLTF Character

  • Geometry

    Generates geometry files from a SOP or DOP network.

  • Geometry Raw

    Generates raw binary files from a SOP or DOP network.

  • HQueue Render

    HQueue, or Houdini Queue, is a distributed job scheduling system.

  • HQueue Simulation

    HQueue, or Houdini Queue, is a distributed job scheduling system.

  • Hair Card Texture

    Renders hair textures for use on hair cards.

  • Karma

    Renders non-USD scenes using Houdini’s Karma renderer.

  • Labs 3D Facebook Image

    Quickly render a 3D scene to a 2.5D image that can be uploaded to Facebook.

  • Labs Flipbook Textures

    Renders, composites, and exports flipbook textures.

  • Labs JSON Exporter

    Export geometry attibutes to a JSON file.

  • Labs Marmoset Export

    The Marmoset Export ROP allows you to quickly generate an mview inside Houdini

  • Labs Niagara ROP

    Export point caches to be used with Unreal’s Niagara particle system.

  • Labs Sketchfab

    Uploads geometry to Sketchfab

  • Labs Vertex Animation Textures

    Exports a mesh and a set of textures to be used with a shader for complex real-time effects, such as: soft-body deformation, rigid-body dynamics, dynamically remeshed geometries, and particle sprites.

  • MDD Point Cache

    This output operator is used to write an MDD animation file.

  • Mantra

    Renders the scene using Houdini’s standard mantra renderer and generates IFD files.

  • Mantra Archive

    Generates disk-based archives which can be used by mantra.

  • Merge

    Merges several render dependencies into one.

  • Net Barrier

    Blocks the ROP network until synchronization occurs.

  • Null

    Does nothing.

  • OpenGL

    Render an image using the hardware-accelerated 3D viewport renderer.

  • Pre Post

    Renders ROPs before and after a main job.

  • Shell

    Runs an external command.

  • Subnetwork

    The SubNetwork output operator provides an easy way to manage large number of output operators.

  • Switch

    Renders one of several inputs.

  • Tractor

    Tractor is a program shipped out with Pixar’s distribution of RenderMan.

  • USD

    Renders a LOP network out to one or more USD files. This node is available as render node or as a LOP.

  • USD Render

    Renders an output image from the stage generated by a LOP network.

  • USD Stitch

    Merges USD files representing individual frames by composing them.

  • USD Stitch Clips

    Merges multiple value clips representing individual frames.

  • USD Zip

    Assembles USDZ archive files from existing USD files.

  • Wedge

    Re-renders the same ROP multiple times with different settings

  • Wren

    This output operator is used to drive the Wren rendering program.

  • glTF