Monday, June 30, 2008

19 Common CG Animation Pitfalls (and counting) ~ Causes and Solutions

Jeremy Cantor - Animation Supervisor - Sony Pictures Imageworks - May 4th, 2002

1) Fearing the technology

Cause: We fear what we don’t understand. Fearing a computer, or believing it is more powerful than it really is comes from not having a fundamental understanding of how a computer works.

Solution: Learn enough about the computer so that you understand its strengths and limitations. Remember that the computer is not a magical device. It can’t think. It just runs programs. It can’t do anything a person can’t do; it can just do things faster. It is only a tool. A very sophisticated pencil. Assuming the user has learned how to speak the computer’s language, the user is the master of the tool, not the other way around.

2) Motion is too robotic…linear.

Cause: Letting the computer simply write linear f-Curves that have no slow-in or slow-out.

Solution: Understand how f-Curves translate into motion. Learn & apply the fundamental principles of animation. Manually insert additional ease-in/ease-out keyframes when appropriate.

(My earliest computer animations were done with software that created linear keyframes and did not have an f-Curve editor. I could not tweak the slope of the curves to create ease-in & ease-out. I had to rely on the application of traditional animation principles and create additional keys to achieve such results.)

3) …or the opposite: Motion is too spliney…watery….”computery”

Cause: Allowing computer to do too much “unsupervised” work. CG software usually creates smooth f-Curves automatically when you set keyframes. “Watery” motion comes from just leaving f-Curves in their default spline shapes. This is why rubber is the easiest thing to animate in CG. Spline f-Curves result in rubbery motion by default.

Solution: Don’t trust the computer to make properly shaped f-Curves. Study how f-Curves translate into movement & manipulate their shapes/slopes accordingly.

4) Characters not displaying a proper sense of weight

Cause: Not understanding the basic principles of timing, slow-in/slow-out, squash/stretch, gravity, etc.

Solution: Don’t let f-Curves just remain in in their default shape after keyframes have been set. The slope of your curves translates to how the forces are acting upon your animated objects. If an object is falling, for instance, make sure your Y-translation curves are accelerating (gravity does not apply itself as a constant force, rather it causes objects to accelerate as they fall). Understand the differences in how characters of varying mass will move. It takes more energy to initiate, stop or reverse the motion of a heavy object or character than it does to do such to a light object or character. Think of the difference in the force it requires to set a bowling ball in motion as opposed to that which is required to initiate the motion of a balloon. And similarly, the force it takes to slow, stop or reverse the motion of such objects.

5) Characters seem off balance.

Cause: Not paying attention to the proper location of character’s center of gravity. Simple physics: A static object’s center of gravity must be directly above or below the point (or average of the points) of suspension, otherwise the object will fall. When a biped character lifts one leg, he must shift his center of gravity over the supporting foot in order to maintain balance. (Variations to this rule apply when the object is in motion, however).

Solution: Pay attention to general physics of center-of-gravity. Study posing and the concept of contraposto. Use yourself as a guide. Study the shifting location of your center of gravity when you transfer your weight from one foot to the other. When you walk. When you run. When you hang from your hands. Etc.

6) Isolated body part movement. Lack of overlap.

Cause: Because it is so easy to animate individual body parts separately in CG, there is a tendency to create movement where separate body parts don’t seem to be working together, or where one part comes to a complete stop before another part begins moving (no overlap). Such inorganic motion also, of course, results from not learning and understanding basic animation principles.

Solution: Study and understand the fundamental principles of animation. Don’t allow all of your keys to remain lined up on the same frames (unless there is a deliberate reason to do so). Work locally but think globally. Always remember that even when you’re focusing on a single limb, it is connected to the rest of the body and all of the parts need to work together, not individually.

7) Twinning (unnatural motion symmetry)

Cause: Twinning is when opposite body parts move as exact mirrors of one another. When the left arm motion starts and stops on exactly the same frames as the right arm. This is usually not desired for natural looking animation (although there are certainly times when it is appropriate) This happens when the animator gets lazy and animates multiple body parts simultaneously, or simply copies/mirrors motion from one limb to another & then leaving the resulting twinned motion as is.

Solution: To avoid twinning, after simultaneously animating multiple body parts or copying/mirroring motion, be sure to go in and add keyframe offsets or other naturalistic variations to the movement.

8) Repetitive or metronomic movement

Cause: Relying too much on the computer’s ability to copy and paste motion. Leaving cycles as is.

Solution: As always, remember that you control the computer, not the other way around. Don’t just blindly copy or cycle movement. Each step in a walk will often be (at least) slightly different from the one before it. Add some naturalistic variation and imperfections (unless of course, repetitive, robotic motion is the desired effect).

9) Squash/Stretch used on inappropriate objects (ie Bowling Balls)

Cause: Learning but not truly understanding the fundamental principles of animation.

Solution: Apply an artistic eye and understand when it is appropriate to apply squash & stretch & when it is not. It is certainly okay to add squash & stretch to a bowling ball, but only if doing so is the result of an aesthetic choice to deliberately bend the rules. It is not acceptable to do such if it is the result of simply applying the fundamental animation principles blindly. It is not enough to simply memorize the principles of animation. You must truly understand them so you can apply them appropriately (or deliberately ignore them if the animation at hand calls for such disobedience in order to most effectively tell your story.)

10) Volume changing when Sqashing/Stretching

Cause: Squashing & stretching an object in CG is a 2 step process. You must scale the object in one axis then oppositely scale it appropriately in the other axes. Neglecting this second step causes the object to appear to shrink when squashing & grow when stretching. Volume changing during squash/stretch is also the result of not truly learning & understanding this fundamental animation principle.

Solution: Learn & understand this principle & don’t forget the second step of scaling in the other axes.

11) Linear wrist/ankle movement (the “marionette look”)

Cause: A wrist does not move from here to there via translation of the wrist itself, rather, such movement is the result of elbow & shoulder (and clavicle…and back…etc) rotations. Therefore the resulting trajectory of a wrist will tend to follow an arc. A wrist can certainly move in a straight line, but that requires simultaneous compensatory adjustments in the shoulder & elbow joint. Such linear movement does occur in such instances as when throwing a straight punch, but the natural tendency is an arc. When animating limbs with IK, the resulting motion often looks like the character is a marionette with its wrists on puppet strings. This is the result of simply animating the trajectory of the IK handles in straight lines.

Solution: One solution is to animate your character’s limbs with FK, which will result in arc motion by default. However, it is often desirable to use IK, so, when doing so, remember to (usually) make the motion an arc. Simply setting an initial translation keyframe at point A then a destination key at point B will result in a linear trajectory and a “marionette” look. Intermediate keyframes are often required to create an arc trajectory. Linear trajectory is okay, assuming that is the intended result. Just remember that such motion is not the normal tendency of a jointed character.

12) Frozen holds

Cause: In traditional cel animation, it if often desirable to completely freeze a character’s motion for dramatic effect. CG animators can sometimes forget that this is one of the few traditional techniques that does not always translate successfully into 3D. Because of the additional dimensionality, the ultra perfect perspective, texture mapping & super-accurate shadow casting (etc) displayed in a 3D CG scene, the viewer tends to have a “higher” expectation of reality. And since very few real-live characters ever actually freeze completely, when a 3D character does so, it can look unnatural and the action of the scene can die completely.

Solution: Use “moving holds” instead, where your character maintains a small degree of motion. Just enough so that the scene doesn’t entirely stop dead, but not too much or the pose will no longer be a “hold”. Perhaps he continues moving ever-so-slightly along his previous trajectory. Perhaps he takes a breath or scratches his ribs. Some animators will put their character’s central pivot point on a very small figure-eight path, so that he will sway just a little bit.

13) Character motion starts & stops exactly in synch with camera cuts

Cause: When an animated scene is made up of several shots, the simplest screen direction for each complete action (or group of actions) to be perfectly book-ended by a camera cut. This creates a scene that looks as if a director had yelled “action” at the very beginning of each shot (just after the camera had started rolling) and then “stop” just before the end of each shot. This is rarely considered good screen direction, as the camera does not appear to be operated by a human being, rather it has the unnaturally cold, perfect & predictable feel of a computer that always miraculously knows exactly when to cut.

Solution: It is usually more visually appealing when the illusion of a human camera operator is created. A human camera operator will suffer from human error. He will invariably end up following just behind the action on occasion, or sometimes actually anticipating it. Overshooting will occur once in a while. Etc. Maintain some degree of overlap between your animation and the camera cuts. Addition of such real world “imperfections” can help to make your scene feel more natural.

14) Arbitrary poses & motions

Cause: The difference between “animating” a character and simply “moving” a character is that “animation” implies life…and character…and purpose. Because of the power of the computer, it’s very easy and often tempting to simply add more & more to your scene simply because you can.

Solution: Remember that every motion of a thinking character must have a purpose. Movement for movement’s sake doesn’t communicate anything & only contributes to unnecessarily increasing the length of your performance and reducing the clarity of the story being told. Ask yourself what is the reason for each pose & motion in your performance. More is not always better. Most often, “elegant simplicity” is the key to telling your story most effectively. The well known acronym KISS means: “Keep it simple, stupid!”

15) Geometry intersections

Cause: Not paying enough attention to the details of your scene. Since CG involves working with virtual objects that are intangible, there is only visual feedback to inform the user when objects intersect one another. Therefore it is sometimes easy to overlook such errors.

Solution: Pay attention.

16) Relying too much on automated processes

Cause: Expecting the computer to do too much of the work for you. With expressions, constraint systems and various other software “bells & whistles”, it is possible to create a variety of automated motions in your characters, such as automatic lagging ponytail bounces that occur whenever the head moves. Such processes usually look automated. Too perfect. Unnatural.

Solution: You should do the work, not the computer. There are certainly occasions where automated processes are effective time savers, but it is very important to implement controls into your character setups that allow you to override or completely disable such processes. This way, even though certain things are happening automatically, you still have ultimate control over them.

17) Unnatural facial animation – not enough shapes, not animating enough parts of the face

Cause: Using too few morph target shapes and animating too few parts of the face. Unless an extremely simplified style is the desired effect, facial animation usually requires a good number of target shapes and plenty of detail in order to effectively create a natural feel to the motion.

Solution: Make enough morph target shapes. Don’t just animate the mouth and the eyebrows. Add appropriate motion to cheeks, eyes, forehead & even ears. Add some corresponding head movement. Apply squash and stretch.

18) Too much camera movement.

Cause: Disregarding the notion that just because you can do something, doesn’t necessarily mean you should. CG software gives you complete control over the motion of your camera. You can add all sorts of crazy camera motion that is extremely difficult or downright impossible in the real world. Because of this power, there is often a temptation to overdo it. Too much camera motion can confuse the action and distract the viewer, and in extreme cases, cause dizziness and queasiness. Sometimes it is certainly appropriate for the camera’s motion to have “character” but it shouldn’t steal the action from the scene (unless the camera is being used as the primary storyteller of that particular shot, like in situations where we are “looking through a character’s eyes”. But such staging should be used sparingly).

Solution: Keep cameral motion to a minimum. Study films and notice that cameras usually don’t move all that much. Sometimes big, sweeping camera motions are appropriate. However, just make sure that you are adding such exaggerated camera motion to help tell the story, and not simply because you can.

19) Motion blur turned up too high

Cause: The motion blur button in your CG software package is a fun toy and, much like the ability to animate your camera, there is an initial tendency to play with it too much.

Solution: Remember, motion blur is an effect that is more sensed than seen. With most motions, you can only see the blurring when you freeze-frame. Watch live action films & you’ll notice that you can only really see blurring when there is extremely fast motion happening. If you can see the motion blur during the normal motions of your characters, it is turned up too high.

The bottom line

a) Study and truly understand the fundamental rules of animation before you start breaking them.

b) Don’t rely on the computer to do too much of the work for you. Remember that the computer is just a tool. You are the artist.

Losing Sleep

A new study may reveal a genetic reason for why people with Fragile X syndrome and autism have trouble sleeping.

If you’ve got rhythm, thank a pair of RNA-binding proteins. A new study in mice shows that the way these proteins function is crucial for synchronizing the biological clocks throughout a person’s body.

The study aimed to understand the source of a symptom in people with Fragile X syndrome, the most common inherited form of mental retardation and the most common known cause of autism. The syndrome is caused by a defect in a gene called fragile X mental retardation 1 or FMR1. People with the syndrome often have unusual sleeping patterns.

Parents often report that it takes two to four years for children with Fragile X syndrome to begin sleeping through the night. Typically developing children usually adopt normal sleep patterns by the time they are six to eight months old.

Many neurological disorders are accompanied by sleep difficulties, says Yung-Hui Fu of the University of California, San Francisco, but the reason for those sleeping problems is often unknown.

An international team of scientists led by David Nelson, a human geneticist at Baylor College of Medicine in Houston, Texas, set out to investigate why. The study appears in the July American Journal of Human Genetics and is the first to suggest a mechanism for the sleep disruptions that accompany Fragile X syndrome.

For eight years, Nelson has been studying FMR1 and two related genes, called FXR1 and FXR2. All three of the genes encode proteins that bind to RNA and help regulate the process that builds proteins from RNA templates.

Previous research had shown that fruit flies that lack the Drosophila FMR1 gene have disrupted circadian rhythms when kept in darkness, but can still reset their biological clocks when exposed to light.

So Nelson and his colleagues tested mice that lack FMR1, FXR2 or both genes to see if their biological clocks are also thrown off. When normal mice are kept in complete darkness, they fall into sleeping-waking patterns slightly shorter than 24 hours. Mice lacking either FMR1 or FXR2 have yet shorter circadian rhythms when kept in the dark, but the difference is subtle, Nelson says. The mice have no trouble resetting their circadian clocks when the lights are turned on.

But mice lacking both genes gave the researchers a big shock — the mice have no circadian rhythm at all in either dark or light. The mice sleep and wake at random times.

“There are no known mutations in the mouse that do this,” Nelson says. Even disruptions of the genes that make up the circadian clock’s gears don’t cause such dramatic disruption of biological rhythms.

When one of Nelson’s collaborators examined the main biological clock in the brains of the mice lacking both genes, the researchers discovered that that clock cycles normally. But circadian clocks in the liver don’t follow the rhythm of the master clock in the brain.

Fragile X protein and its cousin are necessary for synchronizing biological clocks found in every cell in the body, the study suggests.

It also suggests yet another layer of regulation that keeps circadian clocks ticking in unison, Fu says. Scientists have documented the control mechanisms that govern when and how much RNA is produced from the clock genes and described modifications that can affect the function of clock proteins. But researchers have generally ignored the step that controls production of clock proteins, known as translational regulation. The new study may prompt more researchers to explore how protein production affects biological rhythms, she says.


Friday, June 20, 2008

The Seven P's (What I look for in an animator candidate)

Jeremy Cantor – Animation Supervisor – Sony Pictures Imageworks - May 4th, 2002

1) Perception (The MAIN thing)

Overall aesthetic/artistic/creative sensibilities….An "eye".

A grasp of general aesthetics: Composition, camera angles, screen direction, anatomy, posing, design, color theory, etc.

How does one develop such an eye? Years of drawing, painting, sculpting, film-making, studying art, watching movies, observing the world around you, etc. Someone does not necessarily need to be a classically trained "artist" to have a good eye.

This is by far the most important requirement because it is not something that can be effectively taught in the workplace. Candidates absolutely need to arrive with such sensibilities

Many demo reels have animations where the fundamental principles of animation are (all but blindly) implemented by someone who clearly knows their software very well. However, their character design is unappealing, composition is weak, camera angle choices are bad, etc. Such demo reels rarely lead to interviews.

On the other hand, someone who can't necessarily recite Frank & Ollie's 12 basic animation principles and doesn't know Softimage/Maya/3D Studio/etc all that well, but somehow manages to make an entertaining demo reel animation with appealing characters & interesting composition, camera angles & screen direction choices will be much more likely to get an interview.

We can teach someone how to use a particular piece of software...

We can teach someone the fundamental principles of animation….

But we can't teach someone to have a good eye.

Effective self-criticism is also an important aspect of perception. Be able to analyze your own animations and figure out what parts are working and what parts are not, rather than relying too much on your supervisor's critiques as your main catalyst for progress.

2) Principles

A firm understanding of the fundamental principles & mechanics of character animation (anticipation, follow through, squash & stretch, timing, arcs, non-symmetry, 2ndary action, etc). It is not enough for someone to simply be able to list these principles from memory. Candidates must truly understand them and know how and when to apply them properly. These principles should not be implemented blindly. Sometimes certain ones should be exaggerated, toned down or even left out entirely. One must KNOW a rule before it can be broken effectively, creatively and appealingly. If your director tells you to make your character look heavier, do you know which principles need to be adjusted (and how) in order to arrive at such a change?

3) Program Proficiency

At least some rudimentary computer skills and familiarity with a full-featured 3D animation package is desired. However, a gifted animator with very limited computer skills will absolutely be considered as long as he/she has the capacity and willingness to learn the technical part of the job. (Except when deadline pressures don't allow for training time). While we are in fact an "animation" department, for better or worse, we do use computers and therefore, unfortunate as it may seem, even the most amazing animator is of little use to us if he/she is unable or unwilling to (at least partially) animate digitally.

4) Personality & Professionalism

We look for animators who are independently motivated self-starters as well as effective team players. Often, your supervisors are difficult to find (or perhaps out of town) and a candidate must be able to get things done without constant "hand-holding". Also, we work in large, collaborative environment where you never know who you're going to get stuck working with on your next shot or project. If you can't (at least pretend to) get along with just about everyone (at a professional level), you won't last very long. And be aware that this is a relatively small and extremely well-connected industry. Everyone knows everyone. (2 degrees of separation sounds about right). No matter how talented someone is, if they do not play well with others, such word will spread and it will become extremely difficult for them to find work. Furthermore, we like to hire well rounded people who have outside interests and hobbies. We are going to be working very closely together for potentially a long period of time, and we prefer to surround ourselves with potential lunch-mates, not just work-mates.

Be prepared to receive and appropriately respond to criticism (supervisors and directors are not always the most diplomatic folks on the planet). The ability to respond professionally to criticism and failure is often the very thing that separates successful creative people from non-successful creative people. How many times have you heard the story of the author whose million-selling book was initially turned down by dozens of publishers? (ie J.K. Rowling)

A strong interest in the subject matter produced by the studio to which you are applying is also a desired quality as well as a key ingredient for success. These jobs demand that you utilize the full extent of your creative energy for often very long hours in potentially high stress environments. Without a passion for the end product, it will be very difficult to handle such demands for very long. It is unlikely that someone who hates Science Fiction films will ever work above and beyond the call of duty or learn new software on their own time or attempt to "push the envelope" creatively or technically at a Visual Effects studio. Climbing the ladder in this industry requires a lot of creative passion. You will not go far in this business if you are only in it for the money (except perhaps in the executive branches).

5) Problem Solving

Be willing and able to accept and attempt to conquer technical and artistic challenges. When faced with a problem, don't be someone whose first instinct is to run to a supervisor and ask for help. Think creatively…Approach the problem from a different angle..Make a simplified version and do some trial and error. …Pick up a manual.

6) Precision

The teams I tend to work with pride themselves on attention to detail. Candidates should possess such sensibilities as well.

Do you understand the importance of that last ten-percent that turns a good animation into a great animation?

Do you look at the details of your animations with a fine-toothed comb before deciding that they're finished?

Do you check your work for technical glitches, geometry intersections, motion "pops", etc?

Is your resume or cover letter full of spelling errors? If so, can we expect the same level of carelessness in your work?

7) Performance

I find that it is often helpful if an animator has some experience in some form of performing art, especially one that stresses meticulous control of the human body: Gymnastics, dance, martial arts, diving, mime, acting, etc. Folks with such skills tend to have a better understanding of anatomy/physiology/kinesiology and can more effectively break down and evaluate individual body motions at varying levels of detail. Also, such folks tend to be less inhibited when it comes to jumping off their chairs and publicly acting out a performance to more effectively study how their animation should play out. Performers realize that it is okay to dance around like a maniac in the interest of becoming a better animator, and any co-worker who points and laughs is doing so out of jealousy for being too self-conscious to ever do such a thing them self!