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Mapping Actor to Character
Posted: Jun 01, 2007
Published by: the area
Homepage: none
Software: Autodesk MotionBuilder
Category: Character
Skill: Intermediate
Tutorial Steps
2Step 1: Preparing the Scene
3Step 2: Mapping the Actor to the Character
4Step 3: Adjusting the Character


This tutorial guides you through the process of mapping an Actor to a character. When you complete this process, your character will move according to the motion data that was previously defined in the Mapping list.

The major steps of this tutorial are:

Preparing the Scene

Mapping the Actor to the Character

Adjusting the Character

Step 1: Preparing the Scene

In this step, you will add a favorite path for the tutorial folder in the Asset browser window. As a result, you will be able to access the tutorial files directly from the interface.

1. From the menu bar, select File>New, then select Layout>Editing.

MotionBuilder displays a new scene using the Editing layout. This layout displays all the windows you need for your work in this tutorial.

2. Right-click in the Asset browser and select Add favorite path from the contextual menu (fig 53-1).

3. In the Open directory dialog box that appears, choose the BodyA2C folder (created when unzipping the file) and click OK. The BodyA2C folder is added as a favorite path in the Asset browser (fig 53-2, A).

4. Expand the BodyA2C folder in the Asset browser, drag the file actor.fbx (fig 53-3, A) into the Viewer window, and select FBX Open>All Takes from the contextual menu that appears.

An Actor attached to light blue markers appears in the Viewer window (fig 53-3, B). It is the optical motion data in these markers that drive the Actor.

5. In the Transport Controls, select Stance as the current take (fig 53-4, A).

6. Drag the char.fbx file into the Viewer window, and select FBX Merge>No Animation from the contextual menu that appears.

A character named Surfer appears in the scene with the Actor (fig 53-5). Surfer has already been mapped and characterized.

Step 2: Mapping the Actor to the Character

In this step, you will snap Surfer to the optical markers defined in the Mapping list by mapping the Actor to the character. You can make further adjustments using various Character settings.

1. Expand the Characters folder of the Scene browser and double-click Surfer (fig 53-6, A) to display the Character settings in the Navigator window (fig 53-6, B).

2. From the Input Type menu, select Actor Input (fig 53-7, A), then select GymMan from the Input Source menu (fig 53-7, B) if it is not automatically selected.

Actor Input specifies that the Actor you select (GymMan) is the data source.

3. Click the Active option (fig 53-8, A) if it is not already activated to activate and snap Surfer onto the Actor source (fig 53-8, B).

4. In the Transport Controls window, select OpticalMove as the current take (fig 53-9, A).

5. Play the take (Ctrl-Spacebar). The Actor and character move together using the same motion.

In some cases, the movement may not be perfectly aligned between the Actor and the character. You can fine-tune the movement by adjusting certain Character settings, such as Match Source and Reach values.

Step 3: Adjusting the Character

In this step, you will make certain adjustments to your character using the Character settings.

1. Make sure that you are in Models Only display mode in the Viewer window (Ctrl A).

2. In the Character Controls window, disable the Actor (All) option in the Show menu (fig 53-11, A).

The Actor is hidden in the Viewer window, letting you see your character more clearly (fig 53-11).

3. Go to the beginning of the OpticalMove take (Ctrl-Home).

Surfer's shoulders seem too low and close to his body (fig 53-12). You can use the Stiffness settings to adjust the shoulders.

4. In the Character settings, expand Retargeting>Actor>Motion Reduction and select the Shoulder Reduction setting (fig 53-13).

You can use the Motion Reduction settings to adjust the chest, shoulders, neck and head when certain markers are poorly captured, or when the Actor configuration does not provide good capture data.

5. Drag the Shoulder Reduction slider to 80 and observe the more natural appearance of Surfer's shoulders (fig 53-14).

6. Jog (J-drag) between frames 162 and 166, and observe how Surfer's neck juts out unnaturally at frames 165 and 166. You can adjust this movement using the Neck Reduction setting.

7. Select Neck Reduction in the Character Settings, and change the value to 80. Observe the effect on the neck (fig 53-16).

8. Play the take (Ctrl-Spacebar).

Even though you cannot see the Actor in the Viewer window, it is still driving Surfer's movements.


During this tutorial, you linked your character to an Actor with motion data. As a result, the motion data from your Actor drives your character. You can further adjust your character to its source using the options in the Character settings.

Once you are satisfied with your mapping, you can drive the character independently of the optical markers by transferring (plotting) the motion data to your character's skeleton. You can then export your plotted character and open it in other 3D software.

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Posted by cyruspage on Sep 04, 2007 at 06:01 PM
Leaves a lot to be desired as far as matching the motion with good results. When I finished through the tutorial the characters hands were still very far from matching the actor's. With a lot of fiddling, I did get a decent result. Would be nice if tutorial took you all the way through and explained a lot more of the sliders. Is there a more in depth tutorial else where perhaps? However, I do have an understanding of mapping in Motion Builder, however minimal.
Posted by Favian001 on Jun 11, 2007 at 05:19 PM
explains the process nicely.