Understanding Constraints Tutorial

By Ricardo Tobon


The use of constraints is indispensable in 3D animation. It allows for the attributes of some objects to control several attributes of other objects and to turn the connection on or off. Constraints are also some of the main tools in a rigger’s bag of tricks. In motion capture constraints are particularly useful for dealing with character-prop interaction especially if the prop itself was not captured.
This tutorial will cover the basics of using constraints in Motion Builder, but the concepts exposed in it could be applied to any major software packages like Maya, 3DS Max and XSI as they all give the user access to constraints.

Getting Started

Download and open the file Basic_Constraint.fbx. In it you will see two basic primitives, a cube and a sphere. If you play the animation you will see the cube translate from left to right as it rotates and a cone translate upwards also as it rotates.
If you want the sphere to always move and rotate with the cube or cone you could just child it under either one. However if you want the sphere to only move with the cube and not rotate, or if you want the sphere to move with the cube only on certain parts of the animation and move with the cone in certain others, you need to use constraints.

Creating the Constraint

Drag a Position Constraint from the Asset Browser window onto the Viewer window (fig 1).

Fig 1.

A new Constraints dropdown appears on the left side of your Navigator window (fig 2).


Rename the constraint called Position to Sphere_Position by right clicking on the constraint and choosing rename from the popup options.

Setting-Up the Constraint

Double click on the Sphere_Position constraint on the left side of your navigator window to load its options under the Asset Settings area (fig 3).

Fig 3.

Select the sphere and Alt + drag it to the Constrained Object section under the Constraint Settings (fig 4). Select the cube and Alt + drag it to the Source 1 section.

Fig 4.


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