-as a sample, construct a simple bird out of 3 NURB spheres.

-name the wings: right_wing and left_wing (remember to move pivot points of wings to approptiate place)

-parent wings under the body, and name the body Bird

-open the Expression Editor (Window>Animation Editors), name the expression wing_flap, and enter the expression...

right_wing.rotateZ=sin(time*10)*10;

left_wing.rotateZ=sin(time*10)*10;

//the wings now will flap...forever...whenever the play is hit on timeline. The first value 10= flap rate per sec, the other 10 is degrees rotation//

TO KEYRFRAME FLAPPING CONTROL

-pick the Bird node (body)

-add new atttribute (Attribute Editor, Add Attribute)

-name the attribute flap_speed, set min. to 0, Max to 40, default to 0

-update the expression to this new one...

right_wing.rotateZ=sin(time*Bird.flap_speed)*10;

left_wing.rotateZ=sin(time*Bird.flap_speed)*10;

//the new slider in the Bird Attribute Editor can have key set to control the speed, and/or add other connections to other expressions //