Houdini 20.0 Nodes Object nodes

Camera object node

You can view your scene through a camera, and render from its point of view.



Transform Order

The left menu chooses the order in which transforms are applied (for example, scale, then rotate, then translate). This can change the position and orientation of the object, in the same way that going a block and turning east takes you to a different place than turning east and then going a block.

The right menu chooses the order in which to rotate around the X, Y, and Z axes. Certain orders can make character joint transforms easier to use, depending on the character.


Translation along XYZ axes.


Degrees rotation about XYZ axes.


Local origin of the object. See also setting the pivot point .

Modify Pre-Transform

This menu contains options for manipulating the pre-transform values. The pre-transform is an internal transform that is applied prior to the regular transform parameters. This allows you to change the frame of reference for the translate, rotate, scale parameter values below without changing the overall transform.

Clean Transform

This reverts the translate, rotate, scale parameters to their default values while maintaining the same overall transform.

Clean Translates

This sets the translate parameter to (0, 0, 0) while maintaining the same overall transform.

Clean Rotates

This sets the rotate parameter to (0, 0, 0) while maintaining the same overall transform.

Clean Scales

This sets the scale parameter to (1, 1, 1) while maintaining the same overall transform.

Extract Pre-transform

This removes the pre-transform by setting the translate, rotate, and scale parameters in order to maintain the same overall transform. Note that if there were shears in the pre-transform, it can not be completely removed.

Reset Pre-transform

This completely removes the pre-transform without changing any parameters. This will change the overall transform of the object if there are any non-default values in the translate, rotate, and scale parameters.

Keep Position When Parenting

When the object is re-parented, maintain its current world position by changing the object’s transform parameters.

Child Compensation

When the object is being transformed, maintain the current world transforms of its children by changing their transform parameters.

Enable Constraints

Enable Constraints Network on the object.


Path to a CHOP Constraints Network. See also creating constraints.


You can you use the Constraints drop down button to activate one of the Constraints Shelf Tool. If you do so, the first pick session is filled automatically by nodes selected in the parameter panel.


Lookat and Follow Path parameters on object nodes are deprecated in favor of Look At and Follow Path constraints. The parameters are only hidden for now and you can set their visibility if you do edit the node’s parameter interface.



Whether or not this object is displayed in the viewport and rendered. Turn on the checkbox to have Houdini use this parameter, then set the value to 0 to hide the object in the viewport and not render it, or 1 to show and render the object. If the checkbox is off, Houdini ignores the value.

Set Wireframe Color

Use the specified wireframe color

Wireframe Color

The display color of the object

Viewport Selecting Enabled

Object is capable of being picked in the viewport.

Select Script

Script to run when the object is picked in the viewport. See select scripts .

Cache Object Transform

Caches object transforms once Houdini calculates them. This is especially useful for objects whose world space position is expensive to calculate (such as Sticky objects), and objects at the end of long parenting chains (such as Bones). This option is turned on by default for Sticky and Bone objects.

See the OBJ Caching section of the Houdini Preferences window for how to control the size of the object transform cache.


Icon scale

Scales the viewport geometry. This parameter is only for display purposes.


The output resolution in pixels. Standard presets are available via the pull down menu to the right of the parameter.

Pixel aspect ratio

The pixel aspect ratio of the output image.


Type of camera projection used for rendering (for example, perspective or orthographic).


This simulates the classic pinhole camera where camera rays emanate from a common camera origin through a flat camera plane.


This uses parallel camera rays that are orthogonal to the (flat) camera plane. The width of the view volume is determined by the Ortho Width parameter below.

Polar (panoramic)

This projection uses a spherical camera plane for rendering.

Cylindrical (panoramic)

This projection uses a cylindrical camera plane for rendering.

Lens Shader: Use a lens shader to initialize rays for ray tracing.

Selecting Polar, Cylindrical or Lens Shader will automatically switch the Rendering Engine (on the output driver) to Ray Tracing, as it is impossible to render these projections with micropolygon rendering.

Lens Shader

Specifies the CVEX lens shader to use for the Lens Shader projection type. A lens shader is responsible for computing primary rays from screen coordinates, and is a flexible way to define new kinds of camera projections that can’t be modeled as perspective or orthographic projections. Lens shaders can have the following parameters and exports:

float x

X screen coordinate in the range -1 to 1.

float y

Y screen coordinate in the range -1 to 1.

float Time

Sample time.

float dofx

X depth of field sample value.

float dofy

Y depth of field sample value.

float aspect

Image aspect ratio (x/y).

int xres

Image horizontal resolution.

int yres

Image vertical resolution.

export vector P

Ray origin in camera space.

export vector I

Ray direction in camera space.

export int valid

Whether the sample is valid for measuring.

The lens shader should be able to handle x and y values outside the -1 to 1 range, in case samples outside the image need to be generated. The P and I exports should be created in camera space, ignoring the camera transform.

Before rendering begins, mantra measures the lens shader before rendering. During the measuring process, the valid variable can be used to flag invalid rays. In the future, the valid flag may be used during rendering.

Mantra’s camera space is defined with positive z-values in front of the camera, so for a default camera the z-axis is flipped relative to Houdini’s world space.

An example lens shader is the Ray Lens shader.

Focal length

Camera focal length (zoom).

Focal units

The units used for the focal length.


Width of the visible field.

You can obtain a good fit between the Houdini camera and a real world camera by matching a measured lens’s horizontal angle of view, and deriving a Houdini focal length value that reproduces it with the default aperture 41.4214.


The default aperture combined with the default focal length of 50mm produces a 45 degree field of view.

Otho width

Width of orthographic view volume when using Projection is set to Orthographic.

Near clipping

Position of near clipping plane.

Far clipping

Position of far clipping plane.

Screen window X/Y

Define the center of the window during the rendering process.

Screen window size

Scale for expanding the cropped area specified by the Crop parameters.

Screen window mask

Sets the screen window mask to cover the bounding box of the selected object(s).

Left crop

Left cropping margin for camera’s view area.

Right crop

Right cropping margin for camera’s view area.

Bottom crop

Bottom cropping margin for camera’s view area.

Top crop

Top cropping margin for camera’s view area.

Crop Mask

Sets the pixel crop region to cover the bounding box of the selected object(s).


You can optionally add the spare parameter Visible Objects from the Parameter Interface. This allows you to control which objects are displayed in the viewport when looking through the camera.


Shutter time

The shutter time refers to the portion of a frame the shutter is actually open. On a physical camera, this if often referred to as Shutter Speed. The renderer uses this determine motion blur. The value should be in the range [0,1].

A value of 0 for the shutter time would mean that there is no motion blur at all, as the shutter is only “Open” for an instant. A value of 1 on the other hand would mean that the shutter is open for the entire length of the frame.

In the above example the sphere is rotating a full 360 degrees over the course of a single frame. You can see how the length of the “motion trail” or “blur” changes based on the shutter time. In most cases, the default value of .5 is appropriate for animated sequences and a good match for real world settings.

Keep in mind that this parameter controls the amount of time within a single frame, that the shutter is open. It does not refer to how long an individual frame is. To adjust the frame rate, change the Frames per Second parameter in the Global Animation Options.

Focus distance

The lens focal distance and distance from the camera at which objects will be in focus. This is only used when rendering using depth of field. Objects outside this distance will be blurred.


Lens fstop. This is only used when rendering using depth of field. Determines blurriness of depth of field effects.


Filter kernel used in depth of field rendering. Use the pop-up menu to the right of the text box to choose from the available options.

Radial bokeh (radial)

Use a gaussian filter kernel (highest quality).

Image file bokeh (file)

Use an image file

Box filter bokeh (box)

Use a box filter kernal.

Disable bokeh (null)

Do not filter.

Bokeh image file

The file to use for “file” shaped bokeh. White/black cutout images that delineate the shape of the lens are good candidates, where white regions represent the areas that light passes through.

Bokeh rotation

The rotation for “file” shaped bokeh.

For information on transforming sub-cameras, see the Stereo Camera Rig help.

Object nodes

  • Agent Cam

    Create and attach camera to a crowd agent.

  • Alembic Archive

    Loads the objects from an Alembic scene archive (.abc) file into the object level.

  • Alembic Xform

    Loads only the transform from an object or objects in an Alembic scene archive (.abc).

  • Ambient Light

    Adds a constant level of light to every surface in the scene (or in the light’s mask), coming from no specific direction.

  • Auto Bone Chain Interface

    The Auto Bone Chain Interface is created by the IK from Objects and IK from Bones tools on the Rigging shelf.

  • Blend

    Switches or blends between the transformations of several input objects.

  • Blend Sticky

    Computes its transform by blending between the transforms of two or more sticky objects, allowing you to blend a position across a polygonal surface.

  • Bone

    The Bone Object is used to create hierarchies of limb-like objects that form part of a hierarchy …

  • Camera

    You can view your scene through a camera, and render from its point of view.

  • Common object parameters

  • Dop Network

    The DOP Network Object contains a dynamic simulation.

  • Environment Light

    Environment Lights provide background illumination from outside the scene.

  • Extract Transform

    The Extract Transform Object gets its transform by comparing the points of two pieces of geometry.

  • Fetch

    The Fetch Object gets its transform by copying the transform of another object.

  • Formation Crowd Example

    Crowd example showing a changing formation setup

  • Fuzzy Logic Obstacle Avoidance Example

  • Fuzzy Logic State Transition Example

  • Geometry

    Container for the geometry operators (SOPs) that define a modeled object.

  • Groom Merge

    Merges groom data from multiple objects into one.

  • Guide Deform

    Moves the curves of a groom with animated skin.

  • Guide Groom

    Generates guide curves from a skin geometry and does further processing on these using an editable SOP network contained within the node.

  • Guide Simulate

    Runs a physics simulation on the input guides.

  • Hair Card Generate

    Converts dense hair curves to a polygon card, keeping the style and shape of the groom.

  • Hair Card Texture Example

    An example of how to create a texture for hair cards.

  • Hair Generate

    Generates hair from a skin geometry and guide curves.

  • Handle

    The Handle Object is an IK tool for manipulating bones.

  • Indirect Light

    Indirect lights produce illumination that has reflected from other objects in the scene.

  • Instance

    Instance Objects can instance other geometry, light, or even subnetworks of objects.

  • LOP Import

    Imports transform data from a USD primitive in a LOP node.

  • LOP Import Camera

    Imports a USD camera primitive from a LOP node.

  • Labs Fire Presets

    Quickly generate and render fire simulations using presets for size varying from torch to small to 1m high and low

  • Light

    Light Objects cast light on other objects in a scene.

  • Light template

    A very limited light object without any built-in render properties. Use this only if you want to build completely custom light with your choice of properties.

  • Microphone

    The Microphone object specifies a listening point for the SpatialAudio CHOP.

  • Mocap Acclaim

    Import Acclaim motion capture.

  • Mocap Biped 1

    A male character with motion captured animations.

  • Mocap Biped 2

    A male character with motion captured animations.

  • Mocap Biped 3

    A male character with motion captured animations.

  • Null

    Serves as a place-holder in the scene, usually for parenting. this object does not render.

  • Path

    The Path object creates an oriented curve (path)

  • PathCV

    The PathCV object creates control vertices used by the Path object.

  • Python Script

    The Python Script object is a container for the geometry operators (SOPs) that define a modeled object.

  • Ragdoll Run Example

    Crowd example showing a simple ragdoll setup.

  • Reference Image

    Container for the Compositing operators (COP2) that define a picture.

  • Rivet

    Creates a rivet on an objects surface, usually for parenting.

  • Simple Biped

    A simple and efficient animation rig with full controls.

  • Simple Female

    A simple and efficient female character animation rig with full controls.

  • Simple Male

    A simple and efficient male character animation rig with full controls.

  • Sound

    The Sound object defines a sound emission point for the Spatial Audio chop.

  • Stadium Crowds Example

    Crowd example showing a stadium setup

  • Stereo Camera Rig

    Provides parameters to manipulate the interaxial lens distance as well as the zero parallax setting plane in the scene.

  • Stereo Camera Template

    Serves as a basis for constructing a more functional stereo camera rig as a digital asset.

  • Sticky

    Creates a sticky object based on the UV’s of a surface, usually for parenting.

  • Street Crowd Example

    Crowd example showing a street setup with two agent groups

  • Subnet

    Container for objects.

  • Switcher

    Acts as a camera but switches between the views from other cameras.

  • TOP Network

    The TOP Network operator contains object-level nodes for running tasks.

  • VR Camera

    Camera supporting VR image rendering.

  • Viewport Isolator

    A Python Script HDA providing per viewport isolation controls from selection.

  • glTF