Adding Bones to Symbol Objects

Adding Bones to Symbol Objects

Flash CS4 Tutorial


How to Add Bone Structure to Object in Flash



Bones are used to drive character animation or fluid motion such as a flag waving in the wind. They can also be used to simulate wind blown grass or the mechanical articulation of an robotic arm.

Bones are added to objects in multiple ways. It is possible to draw one or more Merge Shape objects, select the entire object, then add the bone structure. For more information on Merge Shapes and adding bones to Merge Shape objects, see topics, Merge Shape and Animating a Flag with Bones.

A second method of adding bones requires that you create your object as a series of Movie Symbols. Once you arrange your Movie Symbols, the bone structure is added with the Bone tool by click-dragging between the symbols. For more information on Movie Symbols, see topic, Movie Symbol Basics.

In this topic we will demonstrate how to add a Bone structure to an object created with several Movie Symbols. This is the first installment of a three part tutorial. Once you add the bones you will want to see Inverse Kinematics - Setting Contraints, then Creating a Walk Cycle with Bones.


Step One

Open a new document and add several shapes to build a side view of a character. You should have a head and torso and a pair of arms, forearms, upper legs and lower legs/feet. There should be ten objects total.

Step Two

Select your objects one at a time and convert each one into a Movie Symbol by pressing F8. Name your objects as you create them for easy identification.

Step Three

Move your body parts in place. Position the legs and arms symmetric about the object's center line.

Step Four

Add a small circle above the head.

Step Five

Select your circle and press F8 to convert it to a Movie Symbol. Name the symbol, Dot.

Step Six

Duplicate your Dot four times (Cmd/d (PC - Ctrl/d) and postion the copies below the feet at the end of the arms. The circles are used to control the rotation angles for the objects at the end of the each IK chain.

Step Seven

Select the Bone tool (x key) and click drag from the torso to the top of a leg. The point where you release is the pivot point for the leg.

Step Eight

Click-drag from the end of the first Bone to the lower leg, then click drag a Bone to the dot below the foot.

Step Nine

Return to the initial Bone and repeat the process for the second leg.

Step Ten

Place your curser over the initial starting point and click-drag up to one of the arms.

Step Eleven

Add additional Bones out to the dot at the end of the arm.

Step Twelve

Return to the initial starting point and repeat the process for the second arm.

Step Thirteen

Return to the initial starting point again and drag a Bone to the head and another to the dot.

Step Fourteen

Choose the Selection tool (v key) and drag the upper arm towards the body to move it's shoulder rotation point to the center of the body.

Step Fifteen

Repeat the process for the other arm.

Step Sixteen

Move the both upper legs so the top pivot point is moved to the center of the body.

Step Seventeen

Select the initial Bone starting point and open the Properties panel.

Step Eighteen

In the Joint: Rotation section, deselect the Enable checkbox. This keeps the shoulders and pelvis in place.

Step Nineteen

Open the Library (Window > Library) and double-click the Dot symbol to open the symbol edit mode. Select the Dot and set the fill and stroke to transparent.

Step Twenty

Using the Selection tool (v key), move the various body parts. To fine tune each pivot point and set the angle contraints, see the next topic in this three part tutorial, Inverse Kinematics - Setting Constraints.

 Where is the Original Object Layer?

Once you click and drag from first Movie Symbol to the second, a new Armature layer is added. The symbols are moved to the Armature layer and the original layer becomes empty.

Once all the objects are connected and moved, it is OK to delete the original layer.

Three Types of Bones

The default Bone shape can be clunky to move. To change the Bone preview shape, click the Armature layer name and open the Properties panel. In the Options section, choose Wire, Solid or Line from the Style pull-down menu.

Using Guides for Accuracy

In this exercise, you could drag guides from the Rulers (View > Rulers) to mark the pivot points for key joints (i.e., upper leg, upper arm). With the guides in place, lock the guides before adding Bones (View > Guides > Lock Guides).