Houdini 20.0 Nodes LOP nodes

Light 2.0

Creates or edits a USD Light prim. This node also adds some useful Karma-specific attributes.

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Since 18.0

Creating vs. editing prims

This node belongs to a class of nodes that create or edit USD prims directly. These nodes operate in Create mode or Edit mode. This is controlled by a Create primitives checkbox or a Create/Edit popup menu. In create mode, the node creates new prims. In edit mode, the node changes the attributes on an existing prim. The Edit mode has two variations. Edit will not modify primitives which have a houdini:editable attribute set to false. Force edit will modify a primitive regardless of the existence or value of this attribute. This attribute can be set on a primitive using the Configure Primitives LOP.

Parameters that correspond to a USD attribute have a pop-up menu to the left that controls how the node authors the attribute.

In addition to that, any connectable USD attributes (i.e., the ones in the inputs: namespace) will have menu items that allow disconnecting them from their sources.

Pop-up menu item

Meaning

Set or Create

Sets the attribute to the given value, whether it previously existed or not.

Set If Exists

Only set the attribute to the given value if it previously existed.

Use this mode to make sure an attribute is only set on primitives of the correct type. For example, only UsdGeomSphere primitives are likely to have a radius attribute.

Block

Makes the attribute appear to not exist, so it takes on its default value. (If the attribute doesn’t already exist on the prim, this does nothing.)

Disconnect Input

Deletes the attribute input connection to its source. Input connections take precedence over attribute values, so disconnecting an input allows the attribute value to take effect.

Do Nothing

Ignore this parameter, don’t create or change the attribute in any way.

Editing lights in the viewport

To...Do this

Enter the Light state

Select the Light node in the network, then in the viewport click the Handles tool, or press Enter.

Mode

Key

Description

Default

⇧ Shift + A

Position the light using handles.

Diffuse

⇧ Shift + D

Click or drag on a surface to place the light normal to that point.

Specular

⇧ Shift + S

Click or drag on a surface to place the light so there’s a reflected highlight at that point.

You should look through the render camera when using this mode, since it only sets the highlight to show up a certain location from the current point of view.

Shadow

⇧ Shift + F

Click on a lit surface to place the pivot point.

This should be on the part of the model you want to control the shadow for (for example, the edge of a window frame, or a prominent feature of the model).

⇧ Shift-click or drag a point on the shadowed surface to move the point on the shadow corresponding to the pivot point.

Look at

⇧ Shift + T

Position the look-at handle to set a look-at constraint on the light. Use the handles to orbit or elevate the light relative to the target point.

This turns on the Enable look at parameter in the Light’s Constraints section.

To constrain the light to look at another USD prim, fill in the Look at primitive parameter.

All

  • ⌃ Ctrl-drag left/right to move light closer/farther.

  • ⌃ Ctrl + ⇧ Shift-drag left/right to change intensity/exposure (see below).

  • mouse_wheel to change step size of ⌃ Ctrl-drags.

  • RMB to show an options menu.

  • Turn on RMB ▸ Keep Brightness to adjust the light to maintain the same brightness on the surface while moving it closer/farther.

  • Turn on RMB ▸ Keep Orientation to prevent the light from rotating as it moves to be normal to where you click on a surface.

  • In the RMB menu, you can choose whether ⌃ Ctrl + ⇧ Shift-drag changes the light’s Intensity or Exposure.

Point Light shelf tool

Adds a point light to the scene. A point light radiates light equally in all directions from a point in space. It is the most efficient type of light to calculate.

Spot Light shelf tool

Adds a spot light to the scene. A spot light casts light from a point in space, in a certain direction. The beam of light is cone shaped, with a radius and falloff at the edges.

Area Light shelf tool

Simulates a light in the shape of a line, rectangle, disk, or sphere.

Geometry Light shelf tool

Simulates a light with the shape and color of a geometry object you select.

Geometry lights can be expensive to render. For simple cases you may want to try to simulate the effect you want using point lights and/or area lights. However, the geometry light is very useful since it’s more straightforward than using tricks with simple lights, and it uses the object’s surface shader to color the emitted light.

  • Select the object you want to emit light, then click the Geometry Light tool on the shelf.

    or

  • With nothing selected, click the Geometry Light tool on the shelf, then select the object(s) you want to act as portals for the environment light and press Enter.

Note

To get geometry lights to emit color based on their assigned surface shader, you need to define an export variable named Ce. This holds the emitted light. You can also use “emission” in the USD Preview Shader.

The object also has to have the “Treat As Light Source” property enabled.

Volume Light shelf tool

Simulates illumination from an emissive volume.

  1. Select the volume geometry you want to emit light.

  2. On the Lights and Cameras shelf tab, click the Volume Light tool.

The volume light takes over the emission (Ce) component, which is treated as direct lighting for the new light source - making it possible to separate it into a distinct per-light deep raster plane separate from the combined direct_emission and indirect_emission planes.

Emission is disabled on the original object for all secondary rays (such as reflections) by disabling the vm_emitillum property on the source object. This ensures only the new light object directly illuminates other objects. (This property is on the Shading tab of the source object if you want to re-enable it.)

Parameters

Sampling Behavior

Cooking this node can generate many USD time samples, rather than just a single time sample at the current time. This can be equivalent to having a Cache LOP following this node, but it will evaluate much faster, and does not cache data from any other nodes. This allows animated data to be authored to USD without introducing a node time dependency which would then cause all following nodes to also be time dependent. This can vastly improve playback performance of some LOP Networks.

In all sampling modes, if a parameter on this node does not vary with time, and does not rely on other time sampled data from the stage, only a single default value will be generated in USD for the corresponding attribute. USD time samples are only generated for parameters that may vary over time.

Sample Current Frame

A single time sample will be generated for the current time.

Sample Frame Range If Input Is Not Time Dependent

If the input to this node is time dependent, this node behaves as if it is in Sample current frame mode. Otherwise it behaves as if it is in Sample frame range mode.

Sample Frame Range

The Start/End/Inc parameter is used to generate multiple times at which this node’s parameters are evaluated, and a USD time sample is created for each attribute at each one of these times.

Start/End/Inc

When the Sampling behavior is Sample frame range, this parameter controls the number and spacing of base time samples to be generated by this node. The default values of this parameter are @fstart, @fend, and @finc. These values correspond to the start, end, and step size of the global Houdini animation settings when interacting with Houdini. When using a ROP node to generate a range of frames, these values correspond to the start, end, and increment values specified on the ROP node being executed. This default ensures that a USD file written to disk will contain time samples for exactly the frame range requested by the ROP (regardless of the Houdini animation settings).

Subframe Sampling

For each primary sample generated by this node, these parameters can cause additional samples to be generated aroudn that primary sample time. This is most often used to ensure that accurate data exists at exactly the camera shutter open and close times, as well as at the primary sample time.

Shutter

Controls the method used to specify the shutter open and close times relative to the primary sample times.

Specify Manually

The Shutter open/close parameter values provide exact offset values relative to the primary sample time.

Use Camera Prim

The Camera prim parameter provides the scene graph path of a camera primitive from which the shutter open and close times are extracted to provide the offset values relative to the primary time sample.

Shutter Open/Close

When the Shutter mode is Specify Manually, these two offset values are added to the primary sample time to indicate the shutter open and close times. The open time should be less than or equal to zero, and the close time should be greater than or equal to zero.

Camera Prim

Scene graph path of a camera prim on the input node’s stage. The shutter open and close attribute values are read from this primitive.

Samples

The number of subframe samples to create for each primary sample. These samples are evenly distributed between the shutter open and close times. Note that such an even distribution may or may not create a sample at exactly the primary sample time.

Always Include Frame Sample

Enable this option to force a sample to be created at exactly the primary sample time. If the Samples values together with the shutter open and close times already place a sample at the primary sample time, turning on this option will have no effect. Otherwise, this option will cause an addition sample to be added. This means that the actual number of samples per primary sample may in fact be one more than the number specified in the Samples parameter.

Action

Whether this node should create new prims, or edit existing prims. In addition, the Force Edit option can be chosen to cause this node to ignore the houdini:editable attribute on prims, and always edit the specified attributes. This is in contrast to the Edit mode which will trigger a warning and not set attributes on prims with the houdini:editable attribute set to false.

Primitive Path

In create mode, this lets you control where in the scene graph to create the prim(s).

The default is usually /$OS. This creates a primitive at the root level with the same name as the node (for example, /tube1). This is a useful default for preventing naming conflicts, but terrible for organization. You should try to remember to change the Primitive path to a better value when you create prims.

For example, instead of naming models after the node that created them, you might want to name them after the geometry inside, and organize them under a /Models branch.

The “Create primitives” section contains basic controls for how to create the new prim(s).

Primitives

In edit mode, the node has a Primitive pattern parameter. This lets you specify the prim(s) the node should operate on. You can click the select button beside the text box to select the primitives from the scene graph tree. You can also use primitive patterns for advanced matching, including matching all prims in a collection.

Initialize Parameters For Edit

In edit mode, changes the state of all control menu parameters to Do Nothing, so that this node will not apply any changes. Also grabs the current values of each property from the first Primitives match, and sets the values of the corresponding parameters to match. This means that changing any parameter’s control menu to Set or Create mode will set the property to its current value, making it easier to apply changes to an existing value rather than setting a brand new value.

Create Primitives

This section only appears when the node is creating primitives.

For example:

  • If you want to create a new cube primitive at /world/objects/cube1 on an empty stage: Set Primitive Specifier to “Define”, and the Parent Primitive Type to “Xform”.

  • If you want to override the radius of a sphere at /world/objects/sphere1: Set Primitive Specifier to “Over”, and the Parent Primitive Type to None. This makes sure the primitive types of any existing ancestor prims are not be modified by this node.

Primitive Count

The number of primitives to create.

Primitive Kind

Set all created prims to have this kind.

Primitive Specifier

The USD operator to use when creating the new prims.

Define

Authors a completely new prim. Use this if you want to create a brand new prim or replace an existing prim.

Over

Authors an override of an existing prim. Attributes not explicitly authored on this prim will get their values from the existing prim on the lower layer.

Class

Define a primitive class. This is usually not necessary unless you are doing deep USD magic.

Class Ancestor

If the Specifier is Define or Over, this parameter will cause some ancestor primitives to be authored with a specifier of Class. This makes it easy to create an Over or Define within a Class without having to use two separate nodes. When the Specifier is Class, this parameter is disabled because the entire primitive hierarchy is already authored as Class primitives.

Parent Primitive Type

If any parents of a path in Primitive paths do not exist, this node will automatically create them. In this case, it will create parent nodes of this type.

Type

Cylinder Light

Light emitted outward from a cylinder. The cylinder is centered at the origin and has its major axis on the X axis. The cylinder does not emit light from the flat end-caps.

Distant Light

Light emitted from a distant source along the -Z axis. Also known as a directional light.

Disk Light

Light emitted from one side of a circular disk. The disk is centered in the XY plane and emits light along the -Z axis.

Geometry Light

Light emitted outward from a geometric prim (UsdGeomGprim), which is typically a mesh.

Point Light

Like a sphere light, but with zero radius.

Rectangle Light

Light emitted from one side of a rectangle. The rectangle is centered in the XY plane and emits light along the -Z axis. The rectangle is 1 unit in length in the X and Y axis. In the default position, a texture file’s min coordinates should be at (+X, +Y) and max coordinates at (-X, -Y).

Sphere Light

Light emitted outward from a sphere.

Transform

Transform

How the transform parameters below apply to the primitive. (Because each USD prim can contain multiple transforms, and be affected by parent transforms, there are many different ways to apply new transforms.)

Append

Apply the parameters as a new, most local transform.

Prepend

Apply the parameters as a new, least local transform.

Overwrite or Append

If a local transform exists with the name xformOp:transform, overwrite it with the parameters. Otherwise, apply it as a new, most local transform.

If this replaces an existing transform, that transform’s order in the local transform stack is not affected.

Overwrite or Prepend

Like “Overwrite or Append”, but least local.

Apply Transform in World Space

Apply the parameters as a new, most local transform. However, prior to applying the transform, it is updated so that the result of the transform appears as if the transform was being applied in world space, before any local or ancestor transformations were applied to the primitive.

Replace All Local Transforms

The transform specified in the remaining transform parameters is always applied as a new transform. Prior to applying this transform, all existing transform operations on the local transform stack are cleared so that only the supplied transform remains on the local transform stack (though ancestor transforms still have an effect).

Transform order

The order in which Houdini applies translates, rotates, and scales, and the order in which it applies rotation.

Translate

Movement amount along XYZ axes.

Rotate

Degrees rotation around XYZ axes.

Scale

Non-uniform scaling along XYZ axes.

Uniform scale

Scales the object uniformly along all three axes.

Pivot Transform

Pivot translate

Moves the local origin of the object.

Pivot rotate

Rotates the local origin of the object after translation.

Base properties

Radius

When Type is Cylinder, Disk, or Sphere, the radius of the light.

Length

When Type is Cylinder, the length of the light from end to end.

Geometry

When Type is Geometry, the path to a geometry prim to use as the light shape.

Width

When Type is Rectangle, the width of the light area.

Height

When Type is Rectangle, the height of the light area.

Angle

When Type is Distant, the angular size of the light in degrees.

As an example, the Sun is approximately 0.53 degrees as seen from Earth. Higher values broaden the light and therefore soften shadow edges.

Clipping Range

Don’t show geometry closer than the near distance or farther away than the far distance (in world units).

Exposure

Scales the power output exponentially as a power of 2, similar to an F-stop control. 0 does not scale intensity, negative numbers scale intensity down by the square, positive numbers scale intensity up. Often you will set the Intensity to what looks like the right amount of light, and then use this parameter to “tweak” it.

Intensity

A linear scale on the power output of the light.

Color

The color of the light, in energy-linear terms.

Texture

Maps a texture to the area geometry of lights. This is currently only supported with rectangular lights.

Enable color temperature

Use Color temperature to control the light color. The color calculated by Color temperature is multiplied by the RGB color in Color, so if you want the “pure” temperature color, you should set Color to 1.0, 1.0, 1.0.

Color temperature

When Enable color temperature is on, the temperature (in degrees Kelvin) to simulate. The valid range is from 1000 to 10000. Lower values are warmer and higher values are cooler. The default is a common white point, D65.

If necessary, you can compute the same color value using the UsdLuxBlackbodyTemperatureAsRgb() function from the USD library.

Normalize power

Divides the set power output (intensity scaled by exposure) by the surface area or angular size of the light. This makes it easier to adjust and compare energy output without it being affected by the size of the light.

Diffuse multiplier

Scales the effect this light has on the diffuse response of shaders. This is a non-physical “tweak”.

Specular multiplier

Scales the effect this light has on the specular response of shaders. This is a non-physical “tweak”.

Scale Guide Geometry

Applies a uniform scaling factor the the guide geometry drawn for the light in the viewport. The default value is an expression that inverts the “meters per unit” value of the USD stage to produce a consistent real-world size for the guide geometry.

Show in Viewport Camera Menu

Turn off this option to prevent this light from showing up in the camera menu in the viewport. This can be useful to hide lights that are embedded in props, or other lights that are not meant to be modified.

Shaping

Spotlight

Add the necessary API to the light to turn it into a spotlight.

Angle

The spread angle of the spotlight beam, in degrees.

Softness

Blurs the edges of the spotlight beam, simulating light leakage and bounce.

Left barndoor

Slides in a light blocker from the left, covering part of the spotlight cone. 1.0 reaches all the way across the cone, blocking all light.

Left barndoor edge

Extends the solid light blocker above by an additional soft edge. 1.0 creates a gradient as wide as the spotlight cone.

Right barndoor

Slides in a light blocker from the right, covering part of the spotlight cone. 1.0 reaches all the way across the cone, blocking all light.

Right barndoor edge

Extends the solid light blocker above by an additional soft edge. 1.0 creates a gradient as wide as the spotlight cone.

Top barndoor

Slides in a light blocker from the top, covering part of the spotlight cone. 1.0 reaches all the way across the cone, blocking all light.

Top barndoor edge

Extends the solid light blocker above by an additional soft edge. 1.0 creates a gradient as wide as the spotlight cone.

Bottom barndoor

Slides in a light blocker from the bottom, covering part of the spotlight cone. 1.0 reaches all the way across the cone, blocking all light.

Bottom barndoor edge

Extends the solid light blocker above by an additional soft edge. 1.0 creates a gradient as wide as the spotlight cone.

Focus (checkbox)

Add the necessary API to the light to be able to focus the beam.

Focus

A control to shape the spread of light. Higher focus values pull light towards the center and narrow the spread. (This is implemented as an off-axis cosine power exponent.)

Focus tint

Off-axis color tint, tints the light in the falloff region. The default is black.

IES

Add the necessary API to the light to use an IES file describing angular distribution of light.

File

An IES (Illumination Engineering Society) format file to use to control angular distribution of light.

Angle scale

A global scale on angles found in the IES file.

Shadow

Enable

When this is on, objects hit by this light will cast shadows (subject to shadow masks).

Color

Tints the color of shadows cast by this light. Changing this from black (0, 0, 0) is a non-physical “tweak”.

Falloff

The near distance at which shadow falloff begins.

The default value (-1) indicates no falloff.

Falloff Gamma

A gamma (i.e., exponential) control over shadow strength with linear distance within the falloff zone (between Falloff and Distance.

Distance

The maximum distance to check for objects shadowing this light. The default is -1, meaning no limit. Setting this may speed up rendering if you know all objects you want shadowed are within a certain distance.

Karma

Active Radius

Houdini render property
karma:light:activeradius

Artificially clamp the illumination distance from the light. Outside this radius, the light will have no effect.

MIS Bias

Houdini render property
karma:light:misbias

Controls whether multiple importance sampling will sample from the BSDF, the light, or both the BSDF and light.

Sampling Quality

Houdini render property
karma:light:samplingquality

This is the per-light sampling quality, that acts as a multiplier on the global Light Sampling Quality. Increasing the quality will add additional samples for this light source, improving the sampling quality of this light relative to other light sources.

Sampling Mode

Houdini render property
karma:light:samplingmode

When using the light tree for rendering, Karma will try to put any light source that’s compatible into the tree. This option can force a light to be excluded from the tree and subject to uniform sampling, which can sometimes yield an improved sampling quality the light at the expense of speed.

Category

Houdini render property
karma:light:category

The category identifier used to select this light source for illumination.

Maximum HDRI Size

Houdini render property
karma:light:hdri_max_isize

If an environment map is larger than this resolution, it will be scaled down when performing texture analysis. If the map has some very small, very bright values, this filtering may affect how sampling of the environment map is performed.

Karma

Rendering

Light Shader

Defines a VEX shader to be used for light evaluation. If the string is empty, the value will be taken from the HOUDINI_VEX_DEFAULT_LIGHTSURFACE configuration variable.

Active Radius

Artificially clamp the illumination distance from the light. Outside this radius, the light will have no effect.

Point Light Radius

As point lights get closer to geometry, the attenuation equation causes the intensity of lights to go to infinity (a singularity caused by the division by the distance between the light and the surface). Increasing this value to something larger than zero creates an artificial buffer zone to prevent the light from going to infinity. If the radius is set to 1, the brightest value for the point light will be twice the intensity specified on the light. If the value is 1.4142 (sqrt(2)), the brightest value will be the intensity specified.

For distant geometry, there should be very little change in the intensity.

MIS Bias

Controls whether multiple importance sampling will sample from the BSDF, the light, or both the BSDF and light.

Sampling Quality

This is the per-light sampling quality, that acts as a multiplier on the global Light Sampling Quality. Increasing the quality will add additional samples for this light source, improving the sampling quality of this light relative to other light sources.

Sampling Mode

When using the light tree for rendering, Karma will try to put any light source that’s compatible into the tree. This option can force a light to be excluded from the tree and subject to uniform sampling, which can sometimes yield an improved sampling quality the light at the expense of speed.

Maximum HDRI Size

If an environment map is larger than this resolution, it will be scaled down when performing texture analysis. If the map has some very small, very bright values, this filtering may affect how sampling of the environment map is performed.

Single Sided

Does the light emit light from a single side (ie along the normal) or from both sides? This only has effect on planar area light types.

Render Light Geometry

Causes the light source geometry to be visible in the render.

Light Geometry Casts Shadow

Causes the light source geometry to cast shadows in the render.

LPE Tag

Custom label assigned to lights or objects for use with light path expression.

Portal MIS Bias

Controls whether the dome light is more likely to sample from the environment map or the portal geometry. For high-contrast HDRI with strong light sources, it may be beneficial to sample more from the environment map (set it less than 0), and for low-contrast/flat HDRI, the opposite may be true (set it greater than 0). Leave it at 0 for balanced approach.

Illuminate Background Holdout

If a light exists to add new light source instead of trying to replicate lighting in the live action plate, enable this parameter so that its effect on background holdout geometry shows up in indirect bounces and its contribution to shadow holdout AOVs is omitted.

Light

Contributions

Provides detailed control over which BSDF component the light affects.

Contributes to Caustics

Default is true. Note that Karma only renders caustics if they are enabled on both the light and the object. This option has no effect unless you also turn on Enable Caustics on the geometry object.

Attenuation Type

Controls the type of attenuation on the light source in the default light shader. This may be: none

No attenuation

half

Half distance attenuation

physical

Physically correct attenuation

Attenuation Start

Minimum light distance to be used for attenuation.

Attenuation

The distance from the light at which Half Distance Attenuation produces half the light intensity.

Spread

Ranges between 0 to 1 and controls beam direction along the light’s normal. A value of 1 results in diffuse emission, and a value close to 0 gives parallel beams of light similar to directional light. Note that the Spread option is only supported for area lights with Type set to Rectangle.

Tips

  • Lights do not generally support non-uniform scale values, so by default the Scale parameter of this node is hidden. In versions of Houdini before 19.0, this parameter was visible, so for backward compatibility, the Scale parameter will be visible if any of the scale components are not 1.0. Reverting this parameter to its default values will cause the parameter to disappear from the parameter dialog.

LOP nodes

  • Add Variant

    Adds one or more variants to a variant set on a primitive. This node creates the primitive if it doesn’t exist.

  • Additional Render Vars

    Create multiple render vars.

  • Asset Reference

    Reference, Transform, and select variants of a USD Asset.

  • Assign Material

    Assigns a material to one or more USD primitives. You can use also programmatically assign materials using VEX, programmatically override material settings for each assignment, and programmatically assign materials to geometry subsets.

  • Assign Prototypes

    Switch point instances or USD instanceable prims to instance a different prototype.

  • Attribute VOP

    Create/edit USD attribute values using a VOP network.

  • Attribute Wrangle

    Create/edit USD primitive attributes using a VEX snippet.

  • Auto Select LOD

    Automatically selects a level-of-detail variant based on the primitive’s distance from the camera.

  • Background Plate

    Sets up hold-out or matte objects that leave holes in the scene through which the background is visible. These prims still take shadows and contribute to reflections as if they were the background.

  • Bake Skinning

    Bakes animation driven by a UsdSkel into transforms and point positions.

  • Basis Curves

    Creates or edits a basis curves shape primitive.

  • Begin Context Options Block

    This node begins a block of LOP nodes, within which certain context options have certain values.

  • Blend

    Partially applies edits to a layer’s attributes based on a fractional weight.

  • Blend Constraint

    Blends transforms according to a list of weights specified as parameters.

  • Cache

    Caches the results of cooking the network at different times, increasing playback speed.

  • Camera

    Adds a USD camera to the scene.

  • Capsule

    Creates or edits a capsule (tube with hemispherical ends) shape primitive.

  • Collection

    Creates/edits collections using primitive patterns.

  • Component Geometry

    Geometry container or import source, in a network created by the Component Builder tool.

  • Component Geometry Variants

    Sets up geometry variants, in a network created by the Component Builder tool.

  • Component Material

    Assigns materials to geometry in a network created by the Component Builder tool.

  • Component Output

    Assembles the final Component prim, in a network created by the Component Builder tool.

  • Cone

    Creates or edits a cone shape primitive.

  • Configure Layer

    Edits metadata on a layer.

  • Configure Primitives

    Edits various metadata on one or more primitives.

  • Configure Properties

    Configures metadata on properties (relationships and attributes).

  • Configure Stage

    Configures metadata for how to load layers into the stage and asset resolution.

  • Coordinate System

    Define named coordinate systems used in shaders.

  • Copy Property

    Copy properties from one primitive to another, or renames properties on a primitive.

  • Create LOD

    Uses the PolyReduce SOP to automatically generate multiple levels of detail from a high-res model, and stores them as USD variants.

  • Cube

    Creates or edits a cube shape primitive.

  • Cylinder

    Creates or edits a cylinder shape primitive.

  • Distant Light

    Creates or edits a USD Distant Light, representing a far-off light source such as the sun. Adds some useful Karma-specific attributes.

  • Dome Light

    Creates or edits a USD Dome Light prim. A dome light emits light inward, simulating light coming from the sky/environment surrounding the scene.

  • Drop

    Runs a simulation to drop primitives under gravity.

  • Duplicate

    Creates copies of a prim (and its descendants).

  • Edit

    Interactively transforms prims in the viewer. Can use physics collisions to position props realistically.

  • Edit Context Options

  • Edit Material

    Allows you to edit an existing USD material by modifying parameters and shader connections. This can be useful if the existing material is on a non-editable layer.

  • Edit Material Properties

    Lets you build a spare parameter interface that reflects material or shader input attributes to directly edit their values.

  • Edit Properties

    Lets you build a spare parameter interface to directly edit attribute and relationship values.

  • Edit Properties From Node

    Lets you refer to the parameter on another node to directly edit attribute and relationship values.

  • Edit Prototypes

    Modify the prototypes of native or point instances in-place, without disturbing the instancing setup.

  • Edit Target Layer

    Allows you to apply edits directly in a lower layer, instead of overriding prims and attributes in the active layer.

  • Error

    Generates a message, warning, or error, which can show up on a parent asset.

  • Explore Variants

    Visualize, set, or extract variants on primitives.

  • Extract Instances

    Converts (heroes) an instance into a real editable prim.

  • Fetch

    Grabs the output of another LOP, potentially in another LOP network.

  • File Cache

    Caches (writes out once and then reads from) USD layers (possibly animated) to disk.

  • Follow Path Constraint

    Constrains a prim to follow a path curve.

  • For Each

    The end node of a For-Each loop block.

  • Geometry Clip Sequence

  • Geometry Sequence

    Imports a sequence of geometry files into LOPs as animated geometry.

  • Geometry Subset VOP

    Creates USD geometry subsets within geometry prims (similar to groups in SOPs) based on evaluating a VEXpression or VOP network.

  • Graft Branches

    Takes prims/branches from the second input and attaches them onto branches of the scene graph tree in the first input.

  • Graft Stages

    Takes scene graph trees from other inputs and attaches them onto branches of the scene graph tree in the first input.

  • HDA Dynamic Payload

    Cooks a OBJ or SOP asset on disk and imports the animated geometry output as a USD payload.

  • Hermite Curves

    Creates or edits a hermite curves shape primitive.

  • Houdini Feather Procedural

    Generates feathers for rendering.

  • Houdini Preview Procedurals

    Invokes Houdini Procedurals while working interactively.

  • Houdini Procedural: Hair

    Houdini Hair Procedural for Solaris.

  • Houdini Procedural: Ocean

    Houdini Ocean Procedural for Solaris.

  • Inline USD

    Parses usda code representing a layer and adds it to the layer stack.

  • Insertion Point

    Represents a point in the node graph where nodes can be inserted.

  • Instancer

    Instances or copies primitives onto points.

  • Instancer

    Create multiple render products sharing common settings.

  • Isolate Scene

    Work in masked areas of the stage.

  • Karma

    Renders the USD scene using Houdini’s Karma renderer.

  • Karma Cryptomatte

    Setup Cryptomatte AOVs for Karma.

  • Karma Fog Box

    Creates a constant volume within a box.

  • Karma Physical Sky

    Creates a Karma Sky Dome and Sun Light rig.

  • Karma Render Properties

    Configure Render Properties for Karma.

  • Karma Sky Dome Light

    Creates or edits a Karma Sky Dome Light.

  • Karma Standard Render Vars

    Create standard karma render vars (AOVs/Image Planes).

  • LPE Tag

    Manage Lights' LPE Tags.

  • Labs Karma AOVs for RenderMan Denoiser

    Generates AOVs for the Pixar RerderMan denoiser.

  • Labs RizomUV Optimize

  • Labs RizomUV Rectangularize

  • Labs RizomUV Unwrap

  • Layer Break

    Starts a new active sublayer that subsequent nodes will edit, and indicates all previous layers will be discarded when saving to disk.

  • Layer Replace

    Replaces all uses of a certain layer with a substitute layer from its second input.

  • Layout

    Provides tools for populating a scene with instanced USD assets. You can place individual components, paint/scatter components in different ways using customizable brushes, and edit existing instances.

  • Light

    Creates or edits a USD Light prim. This node also adds some useful Karma-specific attributes.

  • Light Filter Library

    Authors USD light filter primitives from VOP nodes.

  • Light Linker

    Creates USD light link properties based on rules.

  • Light Mixer

    Lets you interactively edit USD properties for multiple lights.

  • Load Layer for Editing

  • Loft Payload Info

    Adds basic information from inside a payload to the primitive that loads the payload.

  • Look At Constraint

    Constrains a prim to always point toward a target.

  • Mask from Bounds

    Sets a primvar based on whether/by how much selected prims are inside a bounding shape.

  • Match Size

    Resizes and recenters the input geometry to match a reference bounding box.

  • Material Library

    Authors USD material primitives from shader VOP nodes.

  • Material Linker

    Creates material assignments based on rules.

  • Material Variation

    Creates attributes/primvars to override material parameters per-prim/instance.

  • Merge LOP

    Merges the layers from incoming stages into a unified layer stack.

  • Merge Point Instancers

    Merges point instancers into a single consolidated point instancer.

  • Mesh

    Creates or edits a mesh shape primitive.

  • Modify Paths

    Modify asset path attribute values.

  • Modify Point Instances

    Modifies point transforms and property values for individual point instances.

  • Motion Blur

    Adds time samples to allow motion blur when rendering.

  • Null

    This node does nothing. It can be useful to insert a Null into a network as a fixed point in the network that you can refer to by name in expressions/scripts.

  • Output

    Represents the output of a subnetwork. Allows you to design a node asset with multiple outputs.

  • Parent Constraint

    Makes a primitive appear to inherit the transform hierarchy of another prim somewhere else in the tree.

  • Points

    Creates or edits a Points shape primitive.

  • Points Constraint

    Position and Orient primitives using point positions from a geometry.

  • Primitive

    Bulk-creates one or more attributes of a certain type.

  • Prune

    Hides or deactivates primitives and point instances.

  • Python Script

    Lets you write Python code in the node to use the USD API to directly manipulate the stage.

  • RBD Destruction

    An example for a fracturing simulation in USD, also useful as a canned effect.

  • Reference

    References the contents of a external USD files and/or layers created by other LOP nodes into a branch of the existing scene graph tree. Can also remove or replace existing references.

  • Render Geometry Settings

    Applies renderer-specific geometry settings to geometry in the scene graph.

  • Render Product

    Creates or edits a UsdRenderProduct prim, which represents an output of a renderer (such as a rendered image file or other file-like artifact produced by a renderer), with attributes configuring how to generate the product.

  • Render Settings

    Creates or edits a UsdRenderSettings prim, which holds the general settings for rendering the scene.

  • Render Var

    Specifies a custom variable computed by the renderer and/or shaders, either a shader output or a light path expression (LPE).

  • Resample Transforms

    Generates interpolated transform time samples from existing time samples on USD prims.

  • Restructure Scene Graph

    This node has various operations for editing prim paths, variant sets, and composition arcs.

  • Retime Instances

    Offsets and/or scales the timing of animation on selected instances.

  • SOP Character Import

    Imports a character or animation from a SOP network into the USD scene graph.

  • SOP Create

    Lets you create geometry in a SOP subnetwork inside this node, so you can create geometry in-place in the LOP network instead of needing a separate SOP network.

  • SOP Crowd Import

    Imports a crowd from a SOP network into the USD scene graph.

  • SOP Import

    Imports geometry from a SOP network into the USD scene graph.

  • SOP Modify

    Converts USD geometry into SOP geometry, runs the SOP subnet inside this node on the geometry, and converts the changes back to USD overrides.

  • Scene Doctor

    Validates primitives on a USD stage.

  • Scene Import

    Imports models, materials, and lights from the Object level into the LOP network.

  • Scope

    Creates a scope primitive. Scope is the simplest form of grouping, and does not have a transform. Scopes can be useful for organizing the scene tree.

  • Set Extents

    Sets the bounding box metadata of selected primitives.

  • Set Variant

    Selects (switches to) one of the variants stored in a variant set on a primitive.

  • Simulation Proxy

    Generates low-poly collison geometry suitable for physical simulation and creates a proxy relationship to the original model.

  • Sphere

    Creates or edits a sphere shape primitive.

  • Split Point Instancers

    Splits a point instancer into two or more instances, which divide up the original instances.

  • Split Primitive

    Splits USD geometry prims into child primitives based on geometry subsets or primvar values.

  • Split Scene

    This node splits a scene graph into two disjoint sets of primitives.

  • Stage Manager

    Provides a convenient interface to reference in many files at once and place them in the scene graph tree.

  • Store Parameter Values

    Lets you store temporary (unsaved) data in the stage.

  • Sublayer

    Imports from USD files or other LOP node chains into as sublayers, or removes/replaces/reorders existing sublayers.

  • Subnet

    Encapsulates a LOP subnetwork, allowing you to organize and hide parts of the network.

  • Surface Constraint

    Constrain a prim to stick to a surface.

  • Switch

    Passes through one of several inputs, based on a parameter choice or expression.

  • TimeShift

    Outputs the stage as it is at a different point in the timeline.

  • Transform

    Edits the transforms of selected USD primitives.

  • Transform UV

    Moves, rotates, and scales texture coordinates on USD primitives.

  • USD ROP

  • USD Render ROP

  • Unassign Material

    Unbinds a material from one or more USD primitives.

  • Value Clip

  • Vary Material Assignment

    Assign different materials across a number of prims to create variation.

  • Volume

    References volume data on disk into a volume prim containing field prims.

  • Xform

    Creates or edits an Xform prim. Xform (and its sub-classes) represents a transform in the scene tree.