Using the Bone Tool for More Realistic Animations5/26/2010 12:00 AM By Jeff B
You’re using Flash for animations, making some fun (or serious) movies, and you’re frustrated at how long it takes to animate realistic motion with some elements. Fear not—one of the most helpful Flash resources CS4 brought, the “Bone Tool,” has you covered. A strange name for a tool in a computer animation application, but it allows for what’s called inverse kinematic, or IK animations. These are animations that simulate the interactions between limbs, joints, and their other connected components.
Now, the initial thought might be that this is only good for animated animal-like figures (people, pets, etc.), but this can even be used to offer a blade of grass more realism! So you draw a big ol’ cartoon blade of grass, and it’s meant to be blowing in the wind. Before, you had to draw each frame, and the more frames, the smoother the motion.
Instead, select the Bone Tool, and, starting from the base, give the blade of grass a set of “joints” by clicking, dragging, then releasing. This will create a “bone” and “joint.” Click on the end “joint” and drag to set a second joint, and a third, and so on, until you reach the tip of the blade of grass. So now we’ve got a skeleton for our grass, marvelous!
Now we move on to actually generating the IK animation itself. There will be a new layer in your timeline called “Armature” that’s been created for you. Select a frame some ways down the line—maybe frame 80 or frame 120 (so we can get a few seconds of animation at 30 fps), and select the “Insert Pose” menu item. A keyframe is inserted and we get some background color filling up all the frames between frame 1 and the frame you chose.
Pick another frame to insert another Pose and make this one at the halfway point. So now we have two Poses set in addition to the initial (understood) Pose at frame 1. While staying at the frame you just picked to set your second (intermediate) Pose, switch back to the Selection Tool and start dragging your joints around until you have your grass bending at what you expect would be the halfway point. Once you’ve got your grass looking like you expect it would at that particular frame, great! You’re actually all done—the final frame should be identical to the first frame, so as to create a smooth animation.
Go on and preview your delightfully realistic grass blade, and go forth to animate with ever greater realism (and impress your clients with your shiny new bit of web design training)!