Animation Constraints (beta)

Option	Result
Transform Constraint	Allows you to setup a fixed distance constraint between the Driver and Driven xformable’s transforms.
Pin Constraint	Allows you to setup a fixed distance constraint between the Driven xformable’s transform and its closest point on the Driver Mesh
Aim Constraint	Allows one object to point towards another object and track its position as it moves.

Transform Constraint

The transform constraint module is included in the extension omni.anim.xform_constraint. It is about to constrain an object to a certain transform. The source of the transform could be a joint of a skeleton, or a Xformable prim.

A transform constraint can be created between two xformable prims with the following steps:

1. Select two xformable prims. The first one is the driver prim while the second one is the driven prim.

2. Click the Animation/Constraints/Transform Constraint menu to create several ComputeNode typed prims as the children of the driven prim. These ComputeNode prims implement the xformable constraint feature.

3. Note that the relative transform between the driver and driven can be modified after the ComputeNode prims are created.

4. By checking the computeRelativeTransform attribute in the [driven]/xformConstraint/constraint prim, you are free to move either the driver or driven prim. At the time when you uncheck the computeRelativeTransform, the driver and the driven will keep the relative transform as is.

You can also create a constraint between a skeleton joint and an Xformable. First you need to toggle the skeleton visualization from the eye icon as shown in Skeletal Animation. Then just follow the same guide as to constrain two Xformables. The only difference is to select joint prim as the driver prim.

Pin Constraint

In the image above, pinConstraint is created to attach the red cube to preexisting jiggly animation.

Pin constraint is used for sticking Xformable onto a point on mesh surface while maintaining its offset. Example use case is for constraining buttons onto deforming cloth.

PinConstraint Attributes	Type	Result
node:type	Token	OmniGraph node type
active	Bool	Main switch for the node
computeRelativeTransform	Bool	Enable edit mode of the node to live update relativeTransform using current pose
input:masterPrim	Relationship	Driver Mesh
input:slavePrim	Relationship	Driven Xformable
input:masterPoints	Point3fArray	Driver Mesh points
baryCoord	Vec3f	Barycentric coordinate of the surface point
triangleIndices	Int3Array	Driver mesh triangle vertex indices to stick the point on
relativeTransform	Matrix4d	Recorded relative pose between the driven and the surface point. Updated by the node when computeRelativeTransform is True.

Create a Pin Constraint

The Pin Constraint menu will create a PinConstraint OmniGraph node under the driven Prim.

1. Enable omni.anim.pinConstraint extension

2. Select master Mesh (first) and to be driven Xformable (second).

3. Click Animation >> Constraint >> Pin Constraint menu

Aim Constraint

Allows one object to point towards another object and track its position as it moves.

AimConstraint Attributes	Result
computeRelativeTransform	Enable edit mode of the node to live update relativeTransform using current pose
Update Target	Allows you to select the target/driver object
Aim Vector	Sets which axis to point the object along
World Up Type	Select from “Scene, Object or vector” to set preferred Up Vector method - If scene is selected it will default to the stages world up axis
Set World Up Object	If “object” is set as “World Up Type” Click to select an object from the stage to set Up object target. This target can be animated
World Up vector	If “Vector” is selected in “World Up Type” Use these fields to Specify the desired up vector
Maintain offset	The driven object remains at its relative position/orientation when the constraint is applied and does not snap to align the pivot orientations

Create a Aim Constraint

1. Enable omni.anim.pinConstraint extension or In Machinima - access constraints from the animation/constraints menu.

2. To use - Select the first object - Then holding the control key - select the second object.

3. First select the object to be the aim target or driver object.

4. Holding down the control key select the second object. This will be the driven object. Eg camera.

5. On some prims - upon creation of the Aim constraint - The orientation of your driven object may change so its not pointing towards the target. This indicates that prims have different default orientations. Check the “maintain offset” box in the AIM_constraint compute node so the driver object maintains its original orientation.