Chapter 92 16.1 Cartoon physics in the toy world

The great thing about the dinosaurs in the movie is that they have artificial life long enough to be used again as cartoon dinosaurs in the movie Stone Town Paradise. Of course, the reappearing dinosaurs won't be exactly the same.They will be tamer, longer, rounder, and more responsive.However, inside the bodies of these dinosaurs, there was a digital heart beating, a heart belonging to Tyrannosaurus rex or Velociraptor—different bodies, same dinosaur heart.A wizard at Industrial Light and Magic and inventor of virtual dinosaurs, Mark Depp can turn these creatures into adorable pets by simply changing their digital genetic programming while keeping them lifelike for the screen.

Those dinosaurs in the movie are nothing more than walking dead.They have a realistic body, but they lack their own behavior, their own will, their own viability.They are ghostly marionettes manipulated by computer animators.But someday, like Pinocchio, these dinosaurs will get a life of their own. Before these Jurassic dinosaurs came to life in movie worlds, they inhabited an empty three-dimensional world.In this fantasy world, there is almost nothing but volume, lighting, and space.Wind, gravity, inertia, friction, hardness, and the minutiae of the physical world are all absent and require imaginative animators to construct.

"All the physical behavior in traditional animation depends on the cognition of the animator", said Michael Case, a computer graphics engineer at Apple Computer.For example, when Walt Disney drew Mickey Mouse tumbling down the stairs, the effect he showed on paper came from his knowledge of gravity.True or not, Mickey Mouse follows Disney's understanding of physics.This kind of understanding is usually not very real, and this is precisely the charm of cartoons.Many animators resort to exaggeration, mutation, or even simply ignoring the laws of real-world physics for a laugh.However, the modern film style strives for strict realism.Audiences want the flying bikes in the movie ET to look like "real" flying bikes, not cartoon bikes.

What Keith wanted to try was to bring physics into the simulation world. "We took the traditional approach of putting physics into the animator's head, and decided to change it so that the computer also understands some physics knowledge." Let's start with a fantasy world where there is nothing and imagine a floating logo.One of the problems with this simple world, says Case, is that "things in there seem to be light and weightless."In order to increase the realism of this world, we can add mass properties to objects, and set the law of gravity to the environment at the same time.That way, if a floating logo were dropped on the floor, it would fall with the same acceleration as a real object would fall on Earth.The gravity formula is very simple, and it is not difficult to put it into a small world.We can add an elasticity formula to the logo so that it "naturally" bounces off the floor in a very regular fashion.It obeys the laws of gravity, the laws of kinetic energy, and the laws of friction that slow it down.We can also add hardness to it - like the hardness of plastic or the hardness of metal - so that it also reacts realistically to impact.There's a sense of realism to the end result, with the chrome logo bouncing back less and less as it hits the ground until it stops with a click.

We can continue to apply more laws of physics and formulas, such as elastic coefficients, surface tension, and rotation effects, and encode them into the environment.As we add more complexity to these artificial environments, they will become fertile ground for the growth of synthetic life. That's why these jurassic dinosaurs are so realistic.When they lift their legs, they overcome the weight of their virtual torso, and their muscles flex or sag.When the foot falls, gravity pulls on it, and the impact of landing is simultaneously reflected up the leg. The talking cat in Disney's "Scary Ghost," released in the summer of 1993, is also a virtual character similar to a dinosaur, but more realistic.The animators first made the appearance of a digital cat, and then used the cat in a photo as a reference to coat the digital cat with textured fur.If it weren't for its extraordinary ability to speak, it would be very similar to that cat.The movements of its mouth are mirrored from people.So, this virtual animal is actually a cat-human hybrid.

Moviegoers watched as autumn leaves were blown into the streets.What they didn't realize was that the scene was actually a computer-generated animation.The image looks real because there is a certain reality in the image: virtual leaves being blown onto virtual streets by a virtual gust of wind.Like Reynolds' swarm of virtual bats, there's really a lot of stuff that's actually being pushed by a force according to the laws of physics.Those virtual leaves have attributes, such as weight, shape, and surface area.When these leaves are released into a virtual gust of wind, they obey the same set of laws as the physical laws that real leaves obey.Therefore, in this virtual scene, the relationship between the various parts is as real as your body, hair and skin.Although the details of the leaves are not enough to see up close, the falling leaves don't require much painting.

Making animated characters obey their own laws of physics is the new recipe for realism.When the Terminator II droid emerged from a pool of molten chrome, it was shockingly realistic because it obeyed the real-world physics of liquids (such as surface tension).This is a puddle of "simulated" liquid. Case and his Apple colleague Gavin Miller devised computer programs to render the subtle details of a creek trickling down or raindrops falling in a pool.They hooked up the formulas of the various laws of hydrology to an animation engine, and transplanted these laws into the simulation world.In the video clip you can see, in soft light, a shallow wave sweeping across a dry sandy shore, breaking irregularly like a real wave, before receding, leaving behind wet sand.In fact, these are just equations.

For these digital worlds to be useful in the future, everything created has to be reduced to some kind of equation.Not just the dinosaurs and the water, but eventually the trees the dinosaurs gnawed on, the jeeps (in some scenes the jeeps are digital), the buildings, the clothes, the dining table, and the weather.These digital forms aren't just for filmmaking.In the near future, not only movies, but all manufactured products will be designed and produced through computer-aided design software.Today, car parts are already simulated on a computer screen, and the equations are sent directly to the factory's lathes and welding machines to turn those numbers into real shapes.A new industrial process called "auto-forming" takes data from computer-aided design and can generate three-dimensional prototypes directly from powdered metal or liquid plastic in a split second.An object is just some lines on the screen at one moment, and it is already a real thing that can be held in the hand or carried around the next moment.The automatic forming technology "prints" the real gear instead of a drawing of a gear.Emergency spares for factory machines are "printed" on-site in the workshop from crush-resistant plastic;In the near future, this printed part will become a real usable part.John Walker is the founder of AutoCAD, the world's most famous computer-aided design software. He told reporters: "What computer-aided design needs to do is to build models for objects in the real world in the computer. I believe that when the time is ripe, At the time, everything in the world, manufactured or not, could be modeled in a computer. It’s a very, very huge market. There’s everything here.”

Biology is certainly no exception.Computers can already model flowers.Prusinkevich is a computer scientist at the University of Calgary in Canada.He uses mathematical models of plant growth to create three-dimensional virtual flowers.Apparently, the growth process of most plants obeys a few simple laws.Flowering signals can be very complex, and the opening sequence of flowers on the same branch can also be affected by several interactive messages.But it is very simple to program these interacting signals. The mathematical model of plant growth was constructed in 1968 by the theoretical biologist Aristide Lindenmeier.His equation clearly shows the difference between a carnation and a rose: the difference between the two can be reduced to a set of variables for a digital seed.In this way, a complete plant can be represented by a single seed, which only occupies a few kilobytes on the hard disk.When the computer program decompresses the seed, a living flower grows on the screen—green shoots sprout first, then leaves unfold, a bud takes shape, and then, in due course, a flower blooms.Prusinkevich and his students rummaged through the botanical literature to learn how multi-headed flowers bloom, daisies take shape, and elms and oaks produce distinctive branches.They also collected hundreds of growth algorithms for seashells and butterflies.The resulting graphic results are convincing.Prusinkevich's computer-generated image of a blooming lilac could have been used as a photo in a botanical catalogue.

What started as a fun academic exercise at the academy, is now overwhelming Prusinkevich with calls from horticulturists wanting the software.Clients are willing to pay top dollar for software that can show them visually what their landscaping will look like ten years from now, or even as close as next spring. Prusinkevich discovered that the best way to mimic a living creature was to grow it.The growth laws he extracted from biology and applied to the virtual world are now being used to grow the trees and flowers in the movie.The environments they form are a perfect match for those dinosaurs and other digital characters.

Borderlands Software, a respected publisher of educational software for the PC, sells a physics teaching software that models various physical forces.When you launch the physics program in the educational software on your Mac, you can create a toy planet orbiting an on-screen sun.The virtual planet obeys the laws of the toy universe: gravity, motion, friction.By working with dynamics and gravity, students gain a direct feel for the physical processes in the solar system. How much can we cram into this system?Suppose we keep adding to this toy planet the laws of physics it has to obey, like electrostatic gravity, magnetism, friction, the laws of thermodynamics, volume, let's say we keep adding every feature we see in the real world In the software program, what kind of solar system can we finally get in the computer?If a computer is used to make a bridge model—including all forces such as steel tension, wind force, gravity, etc.—can we say that we already have a bridge in our computer?Also, can we add life into it? Physics is penetrating the digital world at a rapid pace, and life is penetrating even faster than physics.In order to see how far distributed life has penetrated into digital movies and what kind of consequences it has produced, I visited several top animation laboratories.