Houdini 16.5 Nodes Object nodes

Blend object node

Switches or blends between the transformations of several input objects.

On this page

The Blend object allows various effects such as blended inputs, animating the parents of objects, sequencing, partial transformation inheritance, three-point orientation, and other effects. It gives you some extra flexibility in setting up parent-child relationships. It operates like the Switch and Sequence blend sops insofar as it takes more than one input and blends or switches those into one output.

Some potential uses of the Blend op are to animate parenting, such as when one character passes an item to another, or to pass on only part of a parents characteristics.

The Blend Object gives you some extra flexibility in setting up parent-child relationships. It operates like the Switch and Sequence blend sops insofar as it takes more than one input and blends or switches those into one output. As with the other objects, such as lights and cameras, the Blend OP can be placed and wired into networks, but its only purpose is to channel data rather than hold it.

Blend allows for a great deal of control over how much influence each of the inputs has over the child object. This can be set either using a weight value for the input or by masking the input to restrict its effect by channels. Each input has its own set of weight and mask controls. There is a special case when you have exactly three inputs which enables the Normal Offset and Orient Axes parameters. The Offset works by moving the child perpendicular to the plane formed by the three inputs; the Orient function rotates the child such that the first input determines the axes center, the second the +X orientation, and the third the +Y orientation.

The Sequence type simply switches between inputs, so the weight and mask controls become inactive. A Sequence value of 0 parents the child to the first input object, a value of 1 parents it to the next, etc. Any value outside the range of inputs will unparent the child.

Parameters

Parents

Type

Method in which parent transforms are combined to produce a unique transform.

Blend

Use Rest Angles

If enabled, this is used when performing shortest path rotation blending to control when flipping will occur. The flipping point will occur when the input orientations differ from the rest angles by more than 180 degrees.

Rotation Blending

This controls the type of rotation blending used. When blending between full rotations (ie. rx, ry, and rz) at the same time, then in addition to Euler, the Shortest Path rotation blending methods are also available.

Euler

Blends each of the rotation components independently.

Shortest Path (Linear)

Use the shortest path when blending rotations between two inputs, with a constant rate of rotation. All 3 rotations (RX, RY, RZ) must be enabled for this option and can only be used when given two inputs.

Shortest Path (Fast Linear)

Use the shortest path when blending rotations between any number of inputs by trading off a constant rate of rotation. All 3 rotations (RX, RY, RZ) must be enabled for this option.

Weight 1

These weights are used to weight each corresponding input parent.

Mask 1

These masks are used to select which component of each parent is used in the blending process.

Rest Angle 1

The world space (euler) rotation values for the Use Rest Angles option.

Rest Angle Order 1

The rotation order for the corresponding Rest Angle values.

Normal Offset

When exactly three parents are input, the child position may be offset in the direction perpendicular to the triangular plane they form.

Orient Axes

When exactly three parents are input this option will orient the child’s local axes to match the orientation of the parents as follows:

First Parent

Axes center

Second Parent

Axes +X

Third Parent

Axes +Y

Sequence

Sequence

When the Type is set to Sequence, this value controls which input parent contributes to the child’s position. It can be used to animate a child from one parent to another. A sequence outside the range of inputs is interpreted as unparenting the child.

Shortest Path Rotation Blending

Use the shortest path possible when blending rotations between two inputs.

Ignore Scales From Inputs

Remove the scales from the input transforms before blending.

Constrain

Sequence

When the Type is set to Constrain, this is similar in operation except no 'popping' occurs when transferring from one parent to another.

Reset Frame

Since this behavior is state-dependent this value allows the child to reset itself (ie. zero any accumulated transform) at the frame.

Transform

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.

Translate

Translation along XYZ axes.

Rotate

Degrees rotation about XYZ axes.

Scale

Non-uniform scaling about XYZ axes.

Pivot

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

Uniform Scale

Scale the object uniformly along all three axes.

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.

Constraints

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

Tip

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.

Note

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 visibitily if you do edit the node’s parameter interface.

Misc

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.

Examples

The following examples include this node.

JiggleMuscle

This example demonstrates how to make a muscle jiggle in object space using a two point muscle.

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.

  • Atmosphere

    Creates a fog effect when rendered.

  • 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 …

  • COP2 Plane

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

  • Camera

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

  • 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

  • Franken Muscle

    Creates a custom muscle by combining any number of geometry objects, muscle rigs, and muscle pins.

  • 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 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.

  • 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.

  • Muscle

    The Muscle object is a versatile tool that can be used when rigging characters and creatures with musculature.

  • Muscle Pin

    Creates a simple rigging component for attaching regions of a Franken Muscle to your character rig.

  • Muscle Rig

    Creates the internal components of a muscle (the rig), by stroking a curve onto a skin object.

  • 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.

  • Pxr AOV Light

    Pxr AOV Light object for RenderMan RIS.

  • Pxr Barn Light Filter

    Pxr Barn Light Filter object for RenderMan RIS.

  • Pxr Blocker Light Filter

    Pxr Blocker Light Filter object for RenderMan RIS.

  • Pxr Cookie Light Filter

    Pxr Cookie Light Filter object for RenderMan RIS.

  • Pxr Day Light

    Pxr Day Light object for RenderMan RIS.

  • Pxr Disk Light

    Pxr Disk Light object for RenderMan RIS.

  • Pxr Distant Light

    Pxr Distant Light object for RenderMan RIS.

  • Pxr Dome Light

    Pxr Dome Light object for RenderMan RIS.

  • Pxr Gobo Light Filter

    Pxr Gobo Light Filter object for RenderMan RIS.

  • Pxr Mesh Light

    Pxr Mesh Light object for RenderMan RIS.

  • Pxr Portal Light

    Pxr Portal Light object for RenderMan RIS.

  • Pxr Ramp Light Filter

    Pxr Ramp Light Filter object for RenderMan RIS.

  • Pxr Rectangle Light

    Pxr Rectangle Light object for RenderMan RIS.

  • Pxr Rod Light Filter

    Pxr Rod Light Filter object for RenderMan RIS.

  • Pxr Sphere Light

    Pxr Sphere Light object for RenderMan RIS.

  • 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.

  • 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.

  • 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.

  • Subnet

    Container for objects.

  • Switcher

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

  • Tissue Solver

    Collects muscles, anatomical bone models, and skin objects and places them into a single dynamics simulation.

  • VR Camera

    Camera supporting VR image rendering.

  • Viewport Isolator

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

  • pxr Int Mult Light Filter

    pxr Int Mult Light Filter object for RenderMan RIS.