Animation Constraints (beta)

Constraints Menu

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

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.

Pin Constraint

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.