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Bone object node

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

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The Bone Object is used to create hierarchies of limb-like objects that form part of a hierarchy or chain of bone objects that are parented to one another. The movement of the chain of Bone objects is "solved" or computed based on several methods including Inverse Kinematics. The parenting attribute of bones is unique in that each bone attaches to the end, not the origin, of the parent bone.

It is recommended that you use the Bones Operation, accessed through the icons above the Viewport, to construct such a chain because placing individual bone objects and establishing their parenting relationships from operator to operator is extremely time consuming and not at all intuitive. In addition, a chain created using the Bones Operation will produce a better behaved bone chain.

By default, bones do not render. They contain two types of display geometry: "link geometry" and "capture region geometry". The former consists of a narrow diamond shape which has been stretched to the length specified in Bone Length, and placed along the Bone Object’s negative Z-axis. The latter consists of two or more user-controllable pill-shaped regions that are used to define capture regions used in skeleton sops. You can specify whether either of the two types of geometry are displayed.

The actual movement of the Bone objects is controlled through an IK CHOP (when using the standard Capture/Deform model). The IK CHOP overrides the bone rotation parameters. If you want to override this behavior, then you need to delete the bone’s channels such that they are no longer over-ridden by chop control.

When bones are parented as children of bone objects, they are automatically positioned at the tip of their parent bone object. If a bone object is parented as the child of a non-bone object, it will attach to the origin of the parent object.

Using Bones

  1. Click the Bones tool on the Characters tab.

  2. Click to place the chain of bones anywhere in the scene view, and continue clicking to add bones to the chain.

    • You can control interior snapping using the Placement menu in the operation toolbar. This is useful for snapping bones to the midline of character skin geometry.

      By default, if a bone intersects a geometry node it will be placed within the geometry based on the view ("View based"). Otherwise the bone will be grounded on the construction plane.

      "Normal based" snaps within geometry based on the geometry normals rather than the view.

      "Freehand" does no interior snapping.

    • You can add, remove, and change kinematics in the drop-down menu on the operations toolbar, or click the bones in the scene view.

      If you create a chain of bones with inverse kinematics a null object will appear at the end of the chain which allows you to easily move the bones while it is grounded by the chain root.

  3. Press Enter to finish the chain.

  4. Name the chain of bones in the Chain Name field on the operations toolbar.

Using Bones

  1. In the viewport, press ⇥ Tab and type Path.

  2. Draw the curve in the viewport.

  3. Make sure the curve is selected, and click the Bones from Curve tool on the Characters tab.

    You can change the Kinematics to Follow Curve in the drop-down menu on the operations toolbar if you want the bones to be bound to the curve. This allows you to modify the curve and the bone chain is automatically adjusted.

  4. Name the chain of bones in the Chain Name field on the operations toolbar.

    You can also increase or decrease the Number of Bones in the chain by changing the value in the value in the operations toolbar.

Parameters

Transform

Translate

Translation along XYZ axes.

Rotate

Degrees rotation about XYZ axes.

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.

Bone

Display Link

Toggles the displaying of the link geometry

Rest Angles

Defines the relative weighting of rotations about the bone’s x,y,z axis for the Inverse Kinematics solver. These values are relative to the bone’s pre-transform. These are zero by default when created from the object viewer’s Bones tool with the pre-transform rotation values defining the rest angles.

Bone Length

Changes the length of the bone

Kinematic Solver

Specifies the CHOP node from which this bone should obtain its cooking rotations from. This requires that the specified CHOP have 3 tracks that are named as: path:rx, path:ry, and path:rz where path is the full path of this bone without the /obj prefix. This path can be obtained using the opsubpath() expression function.

If this parameter is non-empty on a bone without custom geometry, then the display geometry of the bone will be different to indicate this.

The remaining parameters on this page only affect the solutions generated by InverseKin CHOPs using one of the solvers with constraints.

Dampening

Affects how quickly this bone’s angles can be changed.

Angle Range

Specifies the minimum and maximum rotation angles that this bone can have in each axis. (Only used by IK w/Constraints solver)

Damping Angle

Applies damping to the rotation of the bone when the rotation in each axis falls within the specified angle of its minimum or maximum value. The damping occurs when the solved angle is within this angle value from the angle range. (Only used by IK w/Constraints solver)

Damping Rolloff

Specifies the rate at which damping increases as the rotation varies within the damping angle of the minimum or maximum angles. This can also be thought of as the linear slope value at the damping angle region. (Only used by IK w/Constraints solver)

Capture

Capture Region

Display Capture Region

Toggles the display of the /displaycapture capture region

Capture Region Center

Position of the center of the bone’s /ccrcenter[xyz] capture region. Note that this co-ordinate in object-space. Also the z component uses a bone length as a multiplier, thus 0.5 equals half way along the bone.

Capture Region Rotates

rotation of the capture region /ccrrotate[xyz]

Capture Region Scales

Scaling factors. Scaling is performed about the bone local origin in the directions of the local reference frame axes. /ccrscale[xyz]

Capture Top Height

Height of the capture region from the /crtopheight center to the top cap.

Capture Top Cap

X,Y,Z radii of the top hemisphere /ccrtopcap[xyz]

Capture Bottom Height

Height of the region from the center /ccrbotheight to the bottom cap

Capture Bottom Cap

X,Y,Z radii of the bottom hemisphere /ccrbotcap[xyz]

Deform Region

This tab contains similar parameters as capture regions, but they are used for animation and deformation of captured geometry. Notably, the scaling factors can be used to squash and stretch the capture regions during animation.

Capture Bone Length

the length of a bone in the capture mode. This is the bone length when a bone is used for capturing geometry. Note that the capture mode can be turned on by selecting Edit ▸ Objects ▸ Bone Kinematic Override: Capture Pose from the main menu.

Capture Bone Translate

the translation of the bone in the capture mode.

Capture Bone Rotate

the rotation angles of the bone in the capture mode. Note that the bone rotation axis order is ZYX. Rotation together with Translate and Scale parameters form a transformation that positions a bone in the capture position and orientation with respect to the world space. The transform order for this transformation is Scale, Rotate, Translate.

Capture Bone Scale

the scaling of the bone in the capture mode

Render

Display

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.

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.

SimpleIKSolver Example for IKSolver channel node

SimpleInverseKin Example for InverseKin channel node

SimpleTransformChain Example for TransformChain channel node

JiggleMuscle

VexDeform Example for Capture Attribute Unpack geometry node

DeltaMushDemo Example for DeltaMush geometry node

See also

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

    Объединяет данные груминга нескольких объектов в один поток.

  • Guide Deform

    Смещает кривые груминга в соответствии с анимированной геометрией кожи (skin).

  • Guide Groom

    Генерирует направляющие кривые на геометрии кожи и выполняет дальнейшую обработку с использованием редактируемой сети SOP, содержащейся в ноде.

  • Guide Simulate

    Выполняет физическую симуляцию направляющих.

  • Hair Generate

    Генерирует волосы из направляющих кривых и геометрии кожи.

  • 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.

  • Pxr Standard Area Light

    Pxr Standard Area Light object for RenderMan RIS.

  • Pxr Standard Environment Day Light

    Pxr Standard Environment Day Light object for RenderMan RIS.

  • Pxr Standard Environment Map Light

    Pxr Standard Environment Map 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.