Houdini 19.5 Nodes Render nodes

Composite render node

The Composite output operator renders the image(s) produced in the Compositing Editor.

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The Composite output operator renders the image(s) produced in the Compositing Editor.

Arguments may be passed to the scripts and variable expansion is done before calling the script.



Begins the render with the last render control settings.


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

Render with Take

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

Set Valid Frame Range

If on, the render is only valid between the start and end frames, at the specified frame increment. If a frame is outside the range, or falls on a frame that isn’t included by the frame increment, the frame will not be rendered.

If off, the render is valid at any frame.


If you want to temporarily set a sub-range to render, use the 'Frame Range' parameter in the Render Control dialog (click the 'Render Control…' button at the top of this dialog).


COP Path

Path to the COP to render.

Override Default Res

Allows specification of the rendered resolution.


Resolution of rendered images.

Output Picture

Selects where the output is sent.

Image Format

The format to write the image in.

Color Plane

Plane to use as the RGB channels.

Alpha Plane

Plane to use as the A channel (in RGBA image).

Convert to Image Format’s Colorspace

Image data in COPs is always linear. When writing to image formats that are not linear (sRGB, for example), this will convert the colorspace to preserve the look of the image. An 8bit format that has an unspecified colorspace is assumed to be sRGB.

Output Gamma

Gamma correction that is applied to saved images.

Output Frames Reused in Composite

When on, this tells the compositor that output frames may be read back in during the same composite. This disables threaded file writes and batch frame cooking. By default, this is off.

Batch Cook Frames

If on, the compositor cooks frames in groups, rather than individually. This can improve output performance on multi-processor platforms (there is generally no difference for single processor machines). Groups of two frames are recommended when using this option, as the performance gain drops off quickly for larger groups. This option generally uses a bit more memory (instead of a buffer for one file, several are allocated).

Batch cooking speeds up processing of small to medium sized networks, which spend a higher percentage of their time preparing to cook a frame and writing the output image.

Reload All Files

If on, any composite nodes referencing files (such as a File COP) will reload their files. Enable this option if files are being replaced on disk between renders.

Image Area

Output Area

Defines the area to be written to the file. Some file formats support data windows and crop areas (TIFF, Open EXR, pic), which allow you to write portions of an image or extra bordering information. In all cases, the image is written at the resolution specified, but the data window written may be different.

If a format does not support a data window or crop region, the image area requested will be clipped against the image frame. Any data outside the crop region will be black.


The normal image frame area is used, which is what you normally see in the viewport. No data window or crop region is written.

Crop Region

Only data in the crop region is written. All other pixels are set to black. For image formats supporting crop regions, a crop region is set in the file (so it takes up less disk space).

Frame + Surrounding Canvas

This option allows you to write extra image data outside the frame area, so that you can use it when compositing. If the canvas size is less than or equal to the frame area, the frame area is written. In other words, this only differs from the “Frame” option if the COP has a large canvas.

Pixel / UV Crop

Specifies the crop region, in either pixels or UV coords. The fields represent the lower and upper corners of the region (left, bottom, right, top).

Limit Canvas Pixels

If on, the extra canvas information written to the file is limited to this many pixels beyond the frame area. This prevents very large files from being written, and generally gives you the most useful data.

Limit Canvas Percent

If on, the extra canvas information written to the file is limited to a percentage of the horizontal or vertical resolution. So, for a 640×480 image, limiting to 10% will write a maximum of 64 pixels on the left and right, and 48 pixels on the top and bottom.

Auxiliary File 1-5


Save additional images which allows separation of planes into multiple files.


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

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

To run statements from a file instead, specify the path to the file with either a .cmd extension (when the language is set to Hscript), or .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-Render Script

Run this script after all rendering.



Frame being rendered.


Total number of frames being rendered.

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.

  • Brick Map Generator

    Allows you to convert Houdini volume primitives into Pixar brickmap files.

  • Channel

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

  • Composite

    The Composite output operator renders the image(s) produced in the Compositing Editor.

  • 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.

  • 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

    The Vertex Animation Textures ROP will export 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.

  • Render nodes

    Render nodes either render the scene or set up render dependency networks.

  • 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