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PAPERS

Let’s get animated: The introduction to Computer Graphics Course gets animated
by Geordie Swainbank
28 July 2003

1:45 pm, Sunday – Opening day of SIGGRAPH 2003. I was about to embark on a remarkably enjoyable foray into the introductory explorations, and explanations, of “computer animation” through a presentation given by a remarkably enjoyable speaker, Andrew Glassner. It was right after lunch – a time when crowds of computer goers often find themselves tired and uninspired – but as I contorted, bent, squeezed and pleaded my way into a free seat towards the back I could already feel the buzz in the crowd. As soon as he opened his mouth, Andrew had the audience playing right into his hands. By the end of a few well-played jokes and comedic references, we were hanging on every word – we were ready to learn.

Mr. Glassner has been involved with SIGGRAPH since 1985, when he first chaired a course in ray tracing, and although his technical knowledge goes far beyond the reach of many, his talents also lie in other, more visually subjective areas. He began the animation section of the days courses with a claim that often goes overlooked and underappreciated: computer animation, just as in clay animation, is a misnomer for the simple fact that the ‘computer’ doesn’t animate anything, neither does the clay itself possess any notable talent or skill for manipulating itself by… itself. The computer as a tool is a marvelous achievement and gives its operators the benefit of time and money when compared to traditional hand drawn animation and also allows some added benefits over the painstaking process previously done by hand. It is (of course) the person, or persons, behind the machine, behind the putty, that drive the motions which we as critical appreciators of natural movements, take in and analyze.

This is indeed an important part of animation in itself - motion, animation, through the use of high-end 3D packages such as 3D Studio, or MAYA, is an extremely complicated process - not only must the animator know the software in, out, up, down and sideways, but must be able to re-create complicated movements which many of us take for granted. If they were to make a minute mistake with the bending of a knee, ankle, or even toe, we as viewers who are used to seeing these actions hundreds of times a day, will notice and criticize such small incongruencies, thus drawing the viewer back out of their belief in whatever they are watching, whether it be a full fledged cinematic production such as Squaresoft’s Final Fantasy, or the newest 3D action game for your PC.

With this in mind, Andrew brought us back a bit, and returned us to the beginnings of many an animators’ schooling, to the classic ‘bouncing ball’ demonstration. Through the next hour he covered various sections of 3D Studio which are intrinsic to quality animation – from Kinematics to Inverse Kinematics, Dynamics and Particle Systems – he brought us past the bouncing ball to physics based object interaction and even simulated natural phenomenon such as smoke and wind, all of which go into creating the ‘air’ of a quality animation.

In principle, animation on the computer seems relatively simple – make an object, move it and set a keyframe on the timeline. Move it again, set another keyframe at a different time - rinse, repeat. After a while a set of motions is developed and art is born, bearing in mind however the fact we as humans have an exacting eye for accurate and ‘natural’ movement, the process can be excruciatingly complex, but like any beginner, we took it one step at a time.

Andrew started by making a basic sphere and then made a ‘bounce-cycle’ where within a second it moved straight up and down. He then opened a window with a visual representation of the sphere’s movements in space on a graph. With a little animation shortcut he made the up and down movements repeat through time, so now the ball kept up its motion indefinitely. Next he tweaked out the ball’s animation curve so it moved a bit more naturally and finally made it squash as it hit the ground, thus building upon, bit by bit, a series of relatively simple procedures to create a more polished product. Don’t go for everything at once, take it easy. He continued the lesson and finally we had a bouncing ball that repeatedly went around in a circle. He added a little post-production motion blur (a process wherein the computer calculates the position of an object X-number of frames before and after its current position, and adds a blur effect, similar to a motion blur in Photoshop) and voila! Tutorial one done, and in style no less.

But we weren’t finished yet… any object with complicated movements (like legs and hands in the case of humans) which is going to be animated, is usually ‘driven’ by a set of bones. The way one animates these bones is commonly done by one of two ways – either through Kinematics, or Inverse Kinematics (I/K). Take a human leg for example, thigh, knee, shin and foot. Kinematics requires the animator to create bones for any part of a body that rotates, and manually rotate and set a keyframe for each joint. So that’s setting keyframes for a hip, knee, and ankle any time you want motion to change. For I/K, an animator would create an I/K handle with an ‘effector’ that starts at the hip and ends at the ankle. One can manipulate this effector which drives, or calculates, the rotation and position of any joints between the beginning and end points the animator chooses (in this case like I said, the hip and ankle). Now the animator only has to set keys on the effector and ankle, thus lessening the burden of animating more parts, saving time energy and money.

He moved on to explore other amazingly complex portions of the software, like its ‘Dynamics’ set, where one can setup a scene of objects and give them properties like weight and watch them interact with one another in real-time, like objects in real-life do. 10 years ago, according to a truly amusing anecdote Glassner passed along, this process took hours to create and anyone trying to accomplish these goals had to manually calculate the physical properties and physics behind the object interactions. If the simulation didn’t work – recalculate and wait overnight – rinse, repeat. For us though, he created a simplified pencil and pencil holder and set them above ground. He started the simulation and many were amazed at how naturally the two objects interacted to the forces of gravity, the floor below them and even each other.

This section of the introduction to computer graphics course was light-hearted and fun, and on more than one occasion brought the attendees chuckles of delight, along with a solid base from which to begin understanding what those who manipulate the computer into creating quality animation have at their disposal, and how they go about amazing us with their time. Now at least, a few more people understand how patient, persistent, and precise the techniques really are.