Houdini 18.0 Nodes LOP nodes

Karma Render Properties

Configure Render Properties for Karma (Beta).

The Karma Render Properties LOP creates render vars, a render product and a render settings primitive, configured for Karma.

Parameters

Camera

Path to a USD camera (UsdGeomCamera) prim to render the scene from.

Resolution

The horizontal and vertical size of the output image, in pixels.

Instantaneous Shutter

Override the camera’s Shutter close parameter to be equal to its Shutter open time, to produce a zero-width shutter interval. This is a convenient way to disable motion blur.

Aspect Ratio Conform Policy

What to do if the aspect ratio of the output image (Resolution width divided by height) doesn’t match the aspect ratio of the camera aperture (controlled by attributes on the camera). This allows a standard renderer to do something reasonable when you switch between cameras.

Expand Aperture

If necessary, expand the camera aperture to match the image.

Crop Aperture

If necessary, crop the camera aperture to match the image.

Adjust Aperture Width

If necessary, change the camera aperture width to match the image.

Adjust Aperture Height

If necessary, change the camera aperture height to match the image.

Adjust Pixel Aspect Ratio

Change the aspect ratio of the image to match the camera.

Data Window NDC

Directs the renderer to only render within this window of the entire output image. The rectangle is specified in as minX, minY, maxX, maxY, in a normalized range 0 to 1. Coordinates 0, 0 are the bottom left and 1, 1 are the top right. The default window 0, 0, 1, 1 covers the entire image (that is, is not cropped).

You can use this window to temporarily crop the render to a smaller region, for testing purposes.

You can also specify negative values and/or values greater than 1 to reveal overscan data.

Pixels are only rendered if they are fully inside the window.

The normalized coordinates map to the image after any adjustments by the Aspect ratio conform policy.

Pixel Aspect Ratio

The aspect ratio (width/height) of image pixels (not the image itself). The default is 1.0, indicating square pixels.

Screendoor Limit

Images

Output picture

The image or device where the resulting image will be rendered. You can set this value to ip which renders the image in MPlay, or you can save it to an image. The following image types are supported: .pic, .tif, .sgi, .pic.gz, .rat, .jpg, .cin, .rta, .bmp, .tga, .rad, .exr, and .png.

Include $F in the file name to insert the frame number. This is necessary when rendering animation. See expressions in file names for more information.

Output

Color Limit

The maximum value a shading sample is allowed to contribute to an LPE image plane to reduce appearance of "fireflies" caused by undersampling of extremely bright light sources. Note that reducing this value can result in an overall reduction in the amount of light in your scene

Image Filters

Image filters post-process the filtered pixels to produce the final image.

Optix Denoiser

Adds the NVIDIA Optix Denoiser as an image filter.

Use Albedo

???

Use N Input

???

Use Gl Input

???

OCIO

OCIO image filters can be added to various render vars/image planes.

Enable

Enables the OCIO image filter defined below.

Planes

Specify the render var names to which the OCIO image filter will be applied.

Output Space

Specify the OCIO color output space the image filter will apply.

Input Space

???

Looks

???

Sample Filters

Sample filters are used to modify samples before they are sent to pixel filters.

Color Limits

Color Limits can be applied to a number of render vars individually.

Enable

Enables the color limit sample filter defined below.

Planes

Specify the render var names to which the color limit sample filter will be applied.

Limit

The maximum value a shading sample is allowed to contribute to an LPE image plane to reduce appearance of "fireflies" caused by undersampling of extremely bright light sources. Note that reducing this value can result in an overall reduction in the amount of light in your scene

Render Vars (AOVs)

Render vars, otherwise known as AOVs (arbitrary output variables) or additional image planes, can be specified here. By default the beauty, diffuse, glossy reflection, volume, depth, UV and normal render vars are enabled and will write to their respective channels.

Additional render vars can be defined on the node or passed in as render var primitives through the second input for convenience.

Import Secondary Input Render Vars

Enables additional render var primitives passed in through the nodes' second input. When disabled, these won’t be merged into the stage.

Export Components

A whitespace-separated list of shading component names that will be computed for export. If you have defined new component labels in your materials, these can be added to the list so that they are exported for per-component export planes. If you are not using some components, remove them from the list to improve render efficiency.

PBR light exports assume that this list is complete - that is, all components created by shaders are listed. If there are unlisted components, light exports may be missing illumination from these components.

Diffuse Components

A space-separated list of component types that will behave like diffuse bounces. This will affect which reflection scope is used based on the ray type and also which bounce limit to use. Uncategorized component types are assumed to be reflections.

Refract Components

A space-separated list of component types that will behave like refract bounces. This will affect which reflection scope is used based on the ray type and also which bounce limit to use. Uncategorized component types are assumed to be reflections.

Volume Components

A space-separated list of component types that will behave like volume bounces. This will affect which reflection scope is used based on the ray type and also which bounce limit to use. Uncategorized component types are assumed to be reflections.

SSS Components

A space-separated list of component types that will behave like subsurface scatter bounces. This will affect which reflection scope is used based on the ray type and also which bounce limit to use. Uncategorized component types are assumed to be reflections.

LPE (Light Path Expressions)

Standard light path expression render vars

Beauty

Add the beauty output as an RGBA channel labelled C.

Precision

Select between 16 and 32 bit precision.

Beauty Unshadowed

Add the unoccluded (unshadowed) beauty output as an RGB channel labelled beautyunshadowed - defined as unoccluded;C.*.

Diffuse

Add the diffuse surface reflection component as an RGB channel labelled diffuse - defined as C<RD>L.

Diffuse Unshadowed

Add the unoccluded (unshadowed) diffuse surface reflection component as an RGB channel labelled diffuseunshadowed - defined as unoccluded;C<RD>L.

Indirect Diffuse

Add the indirect diffuse surface reflection component as an RGB channel labelled indirectdiffuse - defined as C<RD>.+L.

Glossy Reflection

Add the glossy reflection component as an RGB channel labelled glossyreflection - defined as C<RG>L.

Indirect Glossy Reflection

Add the indirect glossy reflection component as an RGB channel labelled indirectglossyreflection - defined as C<RG>.+L.

Glossy Transmission

Add the glossy transmission component as an RGB channel labelled glossytransmission - defined as C<TG>.*.

Visible Lights

Add the visible lights component as an RGB channel labelled visiblelights - defined as CL.

Emission

Add the emission component as an RGB channel labelled emission - defined as CO.

Indirect Emission

Add the indirect emission component as an RGB channel labelled indirectemission - defined as C.+O.

Volume

Add the volume component as an RGB channel labelled volume - defined as CVL.

Indirect Volume

Add the indirect volume component as an RGB channel labelled indirectvolume - defined as CV.+L.

BSDF Labelled coat

Add the coat component as an RGB channel labelled coat - defined as C<...'coat'>.*.

BSDF Labelled sss

Add the sss component as an RGB channel labelled sss - defined as C<...'sss'>.*.

Ray

Ray Origin (P)

Add the ray origin render var as a Float3 channel labelled rayorigin.

Ray Direction (D)

Add the ray direction render var as a Float3 channel labelled raydirection.

Time (Shutter Time)

Add the shutter time render var as a Float channel labelled time.

Near (Near Bias)

Add the near bias render var as a Float channel labelled near.

Far (Max Distance)

Add the max distance render var as a Float channel labelled far.

Mask (Intersection Mask)

Add the mask render var (alpha) as a Float channel labelled mask.

Contribution

Add the ray contribution render var as a Float channel labelled contribution.

P (World Space)

Add the world space position render var as a Float3 channel labelled P.

Depth (Camera Space)

Add the depth render var as a Float channel labelled depth.

Hitstack

Add the ray hit stack render var as a Float channel labelled hitstack.

Element (Raw Id)

Add the element id render var as a Float channel labelled element.

Prim Id

Add the primitive identifier render var as a Float channel labelled primid.

UV

Add the primitive hit UV render var as a Float3 channel labelled UV.

Hit Dist

Add the primitive hit distance render var as a Float channel labelled hitdist.

dPdz

Add the dPdz (Z-depth delta for the current microvolume) render var as a Float channel labelled dPdz.

N (Smooth Normal)

Add the primitive hit normal render var as a Float3 channel labelled N.

Ng (Geometric Normal)

Add the primitive geometric normal render var as a Float3 channel labelled Ng.

Flags

Add the ray flags render var as a Float channel labelled flags.

Extra Render Vars

Additional render vars can be added on the node directly.

Render Var

Rendering

Sampling

Pixel Samples

The number of ray-samples sent through each pixel. More samples will result in a less noisy image.

Light Sampling Mode

Whether Karma should perform uniform sampling of lights or whether rendering should use the light tree. The light tree can be significantly faster for scenes that have large numbers of lights.

Light Sampling Quality

This is a global control to improve sampling quality for all lights. This acts as a multiplier on the individual light quality controls. Increasing the quality will improve direct light sampling as well as shadows/occlusion.

Random Seed

This is the random seed to use for the render.

Pixel Oracle

When rendering, a Pixel Oracle tells karma which pixels need additional sampling and which pixels are converged.

This parameter tells karma which oracle to use.

Minimum Samples

???

Plane

???

Variance Threshold

???

Headlight

Force Headlight Shading

Disable Lighting

Disable all lighting and material evaluation, using only the display color to shade primitives.

Headlight AO Samples

When rendering in headlight mode, perform this many ambient occlusion samples per shade.

Headlight AO Distance

When rendering in headlight mode with ambient occlusion shading, this distance is used for occlusion testing. Smaller values will result in faster, but less accurate shading.

Headlight Fog Color

The color of the depthcue fog for disabled lighting.

Shading

Ray Bias

The ray-bias used for secondary rays.

Render

Tile Size

Karma breaks down an image into multiple tiles for rendering. This specifies the size of these tiles.

IPR Inc Random

When rendering to the Solaris viewport, this causes each render to start with a new random seed.

IPR Tile Size

The initial tile size for IPR rendering.

IPR Reserve Threads

When rendering in IPR mode, reserve this number of threads for other Houdini tasks.

Cache Limit

Whether to use a fixed size cache (karma:global:cachesize) or whether to use a proportion of physical memory (karma:global:cacheratio)

Cache Memory Ratio

The proportion of physical memory Karma will use for its unified cache.

For example, with the default vm_cacheratio of 0.25 and 16 Gb of physical memory, Karma will use 4 Gb for its unified cache.

The unified cache stores dynamic, unloadable data used by the render including the following:

  • 2D .rat texture tiles

  • 3D .i3d texture tiles

  • 3D .pc point cloud pages (when not preloaded into memory)

Note: This value is only used for off-line rendering, not IPR.

Cache Size (MB)

An explicit memory limit for the unified shading cache. This is deprecated in favor of using the Cache Memory Ratio.

Note: This value is only used for off-line rendering, not IPR.

Dicing

Offscreen Quality

This parameter controls the shading quality scale factor for geometry that is not directly visible to the camera. For geometry that is outside the field of view (ie. visible only to secondary rays), karma will smoothly reduce the shading quality based on the angle between the geometry and the edge of the viewing frustum. Smaller values can increase performance particularly in scenes where the camera is within the displacement bound of nearby geometry, where it permits the hidden primitives to be diced more coarsely than those that are directly visible.

Statistics

Show Alfred Progress

As rendering progresses, print out progress using the Alfred progress format. For multi-frame renders, this progress will be cumulative across frames (i.e. if there are 4 frames, percent complete will be 25% after the first frame finishes).

Driver

Abort Missing Texture

Enabling this option will cause karma to abort the render with an error if it encounters a missing texture map.

See also

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.

  • 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.

  • 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.

  • Bake Skinning

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

  • 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.

  • 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 a collection using selected prims.

  • 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.

  • 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.

  • 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 Properties

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

  • Edit Prototype

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

  • 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.

  • Extract Instances

    Converts an instance into a "real" editable prim.

  • Fetch

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

  • Follow Path Constraint

    Constrains a prim to follow a path curve.

  • For Each

    The end node of a For-Each loop block.

  • Geometry Subset VOP

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

  • Graft

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

  • Inline USD

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

  • Instancer

    Instances or copies primitives onto points.

  • Karma Procedural

    Sets up render-time instantiation for Karma.

  • Karma Render Properties

    Configure Render Properties for Karma (Beta).

  • Karma Standard Render Vars

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

  • LOP nodes

    LOP nodes generate USD describing characters, props, lighting, and rendering.

  • Layer Break

    Starts a new active sublayer that subsequent nodes will edit.

  • Layer Replace

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

  • Light

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

  • Light Linker

    Creates USD light link properties based on rules.

  • Light Mixer

    Lets you interactively edit USD properties for multiple lights.

  • Load Layer

  • Look At Constraint

    Constrains a prim to always point toward a target.

  • Material Library

    Imports Material VOP nodes as USD material prims.

  • 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.

  • Modify Point Instances

    Modify point transforms and property values for individual point instances.

  • 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 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.

  • Reference

    References the contents of an external USD file into a branch of the existing scene graph tree, or removes/replaces 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).

  • Retime Instances

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

  • 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 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 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.

  • 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

  • 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.

  • attribvop