Houdini 21.0 Nodes Render nodes

ML Example Raw render node

Generates raw binary files for ML training from a SOP or DOP network.

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ML Example Raw writes a set of labeled examples to a file to directly use with ML Train Regression. ML Example Raw expects an input geometry consisting exclusively of packed primitives, each of which represents a single labeled example. See ML Example for more details about representing examples using geometry.

This node can be referenced from TOPs using a ROP Fetch to make writing out the data set part of a recipe for doing ML.

See Machine Learning documentation for more general information.

Parameters

Save to Disk

Saves the geometry to disk with the last control settings.

Save to Disk in Background

Starts another copy of Houdini in the background and instructs that copy to cook and save the geometry. This allows you to continue working and load the .raw files as they complete.

Controls…

Opens the control dialog to allow adjustments of the render parameters before rendering.

Valid Frame Range

Controls whether this render node outputs the current frame or the image sequence specified in the Start/End/Inc parameters.

Render Current Frame

Export only the current frame.

Render Frame Range

Export the frames in the Start/End/Inc frame range, but also allow exporting of frames referenced by in-range frames.

Render Frame Range Only (Strict)

Only export the frames in the Start/End/Inc frame range. Do not allow exporting of other frames, including frames referenced by in-range frames.

Start/End/Inc

Specifies the range of frames to render (start frame, end frame, and increment). All values may be floating point values. The range is inclusive.

These parameters determine the values of the local variables for the output driver.

$NRENDER

The number of frames to be rendered by the output driver.

$N

The current frame being rendered (starting at 1 and going to $NRENDER).

Render with Take

Uses the settings in a particular take while rendering. Choose Current for the current take when rendering.

SOP Path

The SOP node, object, or SOP subnet to render from.

Output File

The file to save the binary data. The extension doesn’t matter so it depends on what system reads it. A .raw is often used to make it clear it isn’t a defined format.

Transform

Specifies if the geometry should be transformed into world space before being written.

Labeled Examples

Number of Inputs

Type

Type of input contribution: either a point attribute or a volume.

Point Attribute

Name of a point float attribute.

Volume Name

The name of a volume.

Number of Targets

Type

Type of target contribution: either a point attribute or a volume.

Point Attribute

Name of a point float attribute.

Volume Name

The name of the volume.

Render Settings

Create Intermediate Directories

When turned on, creates intermediate parent directories for output files as needed. Currently only applies to generated scripts, images, and shadow maps.

Initialize Simulation OPs

Forces all simulation OPs to be reset. This includes DOP Networks, POP SOPs, and other OPs that cache their results.

This is the safest way to render out a simulation because it starts the simulation from scratch and discards any partial simulations with different parameters.

Alfred Style Progress

A percentage complete value is printed out as files are written. This is expected by Pixar’s Alfred render queue.

Report Network Use

The number of bytes sent or received by the distributed simulation primitives during the cooks triggered by this geometry output is printed.

This does not track used by. For example, saving a file to an NFS mount. It only tracks the network communication of nodes such as the Gas Exchange Border DOP.

Save Retries

Sets the number of times Houdini re-attempts to save. Houdini usually errors the output node immediately when saving the geometry to disk fails due to a disk writing error. For most cases, this works because it’s an illegal path which is not recoverable. However, it sometimes failes due to network issues. The console outputs the failure to save and waits five seconds for the network to clear up.

Save in Background

When saving more than one frame, save in a background thread. Faster for large file sizes but may use more memory since it retains the output geometry until the save completes.

Scripts

A script command can be specified for execution at various execution points. The expression language selected for the script parameter determines whether the command is in hscript or python.

Prior to execution, this node is automatically set as the global current node.

To run statements from a file, specify the path to the file with either a .cmd extension (when the language is set to Hscript) or a .py extension (when the language is set to Python). Additional arguments to the script can also be supplied. They will be parsed in a shell-like manner.

Pre-Render Script

Run this script before any rendering.

Pre-Frame Script

Run this script before each frame.

Post-Frame Script

Run this script after each frame.

Post-Write Script

Run this script after each frame’s data finishes writing to disk.

Post-Render Script

Run this script after all rendering.

Post-Write Script

Run this HScript after each frame’s data has finished writing to disk. This is always after the corresponding Post-Frame Script and always before the Post-Render script, but the order is undefined. When Save in Background is on, allows delaying script actions until the file has finished saving.

Locals

N

Frame being rendered.

NRENDER

Total number of frames being rendered.

See also

Render nodes

  • Agent

    Writes 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

    Exports animation from a geometry-based skeleton to an FBX file.

  • Filmbox FBX Character

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

  • Flipbook

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

  • 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.

  • Image

    Writes the output of a COP network to disk.

  • 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.

  • Labs ZibraVDB Compress

    Compresses a VDB sequence and caches it to disk as a single .zibravdb file.

  • MDD Point Cache

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

  • ML Example Raw

    Generates raw binary files for ML training from a SOP or DOP network.

  • 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