Create any combination and number of point and orientation constraints on an object.
Create a constraint on an object
How to apply a restriction to a DAG node.
The term constraint describes a generalized restriction that can apply to any DAG node. A point constraint modifies the translations of an object to match the position of the object it is constrained to. Orientation and aim constraints modify the rotations of the constrained object so that its local axes match those of the constraint object (orientation), or the selected aim axis points at the constraint object (aim).
translates or rotates the object that is being constrained to the position and orientation of the constraint. You can create any combination and number of point and orientation constraints on an object. You can also copy and mirror existing constraints onto a skeleton.
Create a constraint
- Choose an object using Pick > Object, or pick an object DAG node in the SBD window.
- Choose Animation > Tools > Create Constraint from the menu bar.
Depending on the you have set in the window. You are prompted to pick either a joint or a node.
For example, the system prompts:
Pick a joint or node to constrain.
- Pick an object in the modeling or SBD window. You will see a selection handle or a jack (or both) appear next to the object, allowing you to use the new constraint.
Hints and Tips
In general it is not useful to apply a constraint directly to a skeleton joint. For example, if a point constraint is applied to a joint, moving the constrain object would cause the bone to stretch. Normally, you should create IK handles (using Animation > IK > Add IK Handle) and then constrain the IK handle to an object. To make it easier, if Animation > Tools > Create Constraint is applied to a skeleton joint, an IK handle is created and a null node is added in the SBD window.
Grouped IK manipulation example
Baking animation and using Motion Blur compensation
There will be times when you will want to generate animation curves from the constraint animation. creates animation curves with keyframes at regularly specified intervals. You can view theses curves and edit them by hand.
Constraint animation is limited to a -180/+180 degree range. If the constraint jumps from -180 to +180, the object doesn’t actually move. However, the motion blur sampling reads a value between those degree ranges, and the object appears to flip. With , extra keyframes are created with the at the motion blur sample times, wherever this flipping problem is detected. The sample points are at the frame, plus/minus the following value:
(RenderByFrame * ShutterAngle) / 720
Notes and tips
- When Alias is saving out an SDL file, IK and constraint animation is written only for the range of keyframes specified in the Render Globals window.
This means that if you edit the start/end frames in that SDL file, you won’t have the constraint/IK animation outside the original start/end range.
You must re-save the SDL to get any missing constraint/IK animation.
- The effects of invisible constraints are inconsistent. A constraint to an invisible object is not evaluated during playback, but is enforced during transformation of the constrained object.
Use Animation > Edit > Constraints On/Off to enable/disable constraint updates instead of visibility.
Constrain one object to another object
Create UV point, orientation or aiming constraints on an object.
creates constraints that translates or rotates the constrained objects to the position. You can create any combination and number of UV point, orientation, or aiming constraints on an object.
Constraining an object to another object
- Select an object using Pick > Object, or pick an object DAG node in the SBD window.
- Choose Animation > Tools > Constrain To.
The system prompts depend on the constraint type that you have set in the window.
- If the is (the default), the system prompts:
Pick the DAG node whose rotate pivot will be a POINT constraint for the selected node.
- If the is , the system prompts:
Pick the DAG node which the node’s local x axis will AIM at.
- If the is , the system prompts:
Pick the DAG node whose local axis will be an ORIENTATION constraint for the selected node.
- Pick an object in the modeling or SBD window that meets the criteria outlined in the prompt.
In the modeling view, a line may be shown to indicate the constraint. This line is only shown if the constraint is not met.
- Create two primitive spheres and a jack using Surfaces > Primitives > Sphere and Animation > Tools > Jack.
- In the Animation > Tools > Constrain To), make sure the option is clicked . window (
- With the jack active, choose Animation > Tools > Constrain To and pick the sphere at the left.
Notice how the jack moves to the sphere that it is constrained to:
- With the jack still active, choose and pick the sphere at the right.
Notice that the jack moves between the two spheres.
The jack is equidistant from the spheres because the weight of the constraints is equal. If the weight of one constraint was greater, the jack would be closer to the sphere with the greater weighted constraint. To change the weight, use Windows > Information > Information Window.
- Pick nothing, then pick the sphere at the right.
The jack changes color to show it is constrained to the selected sphere:
- Move the active sphere and then pick and move the sphere to the left.
The jack moves in relation to the two objects it is constrained to:
Hints and tips
In general, it is not useful to apply a constraint directly to a skeleton joint. For example, if a point constraint is applied to a joint, moving the constraint object stretches the bone.
Normally, you should create IK handles for a skeleton joint (using Animation > IK > Add IK Handle) and then constrain the IK handle to an object. To make this easier, if Animation > Tools > Constrain To is applied to a skeleton joint, an IK handle is created and constrained to the selected object.
Edit UV constraints
How to pick and modify any UV constraint assigned to a constraint target object.
Edit UV constraints
- Choose Animation > Tools > Edit UV Constraint.
- Pick the UV constraint target object or constrained object.
All of the UV constraints related to the picked object will be displayed as markers.
- Pick a UV marker or -select an object. The marker is picked when it turns red.
- Click the UV marker and move it or enter the UV coordinates in the prompt line.
You can also edit a UV constraint from the by opening the section.
Turn constraints on or off
Use Animation > Edit > Constraints On/Off to enable or disable constraints.
When a constraint is OFF, it behaves as if it does not exist.
This function makes it easier to turn on or turn off a group of constraints. For example, you can toggle states of all existing constraints without picking any of them; set constraints of a group of active objects to be the same state; make changes only on the selected types of constraints (say, only change point constraint); or make changes only to the constraints of your picked hierarchies. You can choose to use the constraints either on the constrained side, or the constraining side of the objects.
To turn constraints on or off
An individual constraint can be turned or from the Information Window when the constrained object is picked.
- If the Active option is on, pick the objects whose constraints you wish to affect.
- Choose Animation > Edit > Constraints On/Off to set their states ( or according to the options’ setup.)
Turn constraint display on and off
Use Animation > Show > Constraints to display the constraints on your model while you are working on animation improvements.