I went to "The Science Behind Pixar Exhibition" at the California ScienCenter, and it was INSANELY COOL.
The exhibit hosted recorded interviews from Pixar employees on "What's it like to work at Pixar", hands-on demos on each part of the production pipeline––my favorite was the simulation demo: Pixar rendered clips from some of their movies with and without certain simulations (hair/fur, water, crowds) and gave the museum guest the power to switch back and forth between the same scene with and without the simulations.
The drive down to LA from SJ was 5 hours, but honestly I'd do it again just to see this exhibit alone. Maybe one day I'll be in one of the black boxes in the exhibit talking about what I do at Pixar... :)
To create this animation, I used Dragonframe and my DSLR to capture the frames, and After Effects to put the frames together and export as a video. The motion and physical posing was done using my bare hands. Unfortunately, I recorded an extensive amount of video and did not have the time to edit it all, so I chose the clip with the most movement as my animation.
Character Animation from Justin Tennant on Vimeo.
Gravity! It’s that invisible force keeping us all anchored to this lovely home we call Earth. The effects of gravity combined with other known properties of physics such as inertia and air resistance give us the physics of trajectories, otherwise known in the animation world as paths of actions. When we toss a ball up in the air, we expect it to rise and decelerate to a peak point, then fall and accelerate until we catch it, following a parabolic path. This is a fairly intuitive and natural property of physics: moving objects will display parabolic paths of actions due to the force of gravity, with their arc curves and lengths determined by their inertia and drag amount due to air resistance.
Say for instance, a ball is thrown in the air. Due to gravity, the ball quickly decelerates as it rises. As it reaches the apex height, instead of stopping, it continues rising for a few seconds at a constant slow velocity. Then suddenly, the ball drops as normal. Strange behavior, right? Such a deviation of standard “physics protocol” would be very visually noticeable - an observer would surely spot the odd floating ball, and maybe remark about forgetting to take their pills. Oddities like this don’t ever happen in real life (thank goodness), but they certainly do happen in fictional worlds artists create, like in films and movies. Sometimes erroneously, and sometimes intentionally, filmmakers have occasionally forgone the rules of paths of actions in their visual creations. This has resulted in clips and scenes that, had the clip or scene played out in real life, the moving objects would have had very different arcs, and thus, very different overall outcomes. Here we begin our analysis of three separate films, each chosen with one physics-defying scene that illustrates an improper path of action.
Los Angeles, CA – the year is 1994. A certain Hollywood actor Keanu Reeves is starring in an action thriller film Speed, in which a certain bus has been rigged with explosives. Keanu, an LA city cop, is told by the bomber via phone that if the bus accelerates to 50 mph or more, the bomb will activate, and if the bus then decelerates to 50 mph, the bomb will detonate. Keanu races to said bus, just barely making it aboard when the bus hits 50 mph. Plot and certain small events happen onboard the bus. What’s important to know is that Keanu manages to keep the bus above 50 mph through it all – nicely done Keanu.
Until the bus approaches this: the unopened 105 Freeway. Keanu learns that a portion of the freeway is incomplete – on the overpass the bus is heading towards, there is a sizable gap separating one side of the overpass from the other. With his keen Hollywood logic and LA cop bravery, Keanu forces the driver to put the petal to the metal in an attempt to jump the gap. The scene is tense, thrilling, and undoubtly entertaining – the bus slowly accelerates, approaches the gap, and… raises into the air? Huh? Let’s take another look at this scene.
At the moment the bus’s front wheels approach the edge of the gap, the entire front of the bus suddenly rises up, as if there was a perfectly angled ramp placed conveniently on one side of the gap. But in the shot displaying the gap, there is no ramp to be found. Could it have been an act of God, a helping hand from an otherworldly deity, who ever so slightly tugged an invisible string attached to the front of the bus, leading Keanu and his people to safety? Perhaps so. But in reality, if the bus were to approach the gap with no ramp in sight, the bus would have no lifting force to propel its front up as seen in the movie. Rather, the inertia of the bus would cause it to continue moving straight forward past the edge of the gap. At the same time, the heavy weight of the bus (aka gravity) would cause the bus’s pitch (aka lateral axis) to tilt downwards, along with its velocity, leading to a parabolic path of action headed downward for the bus and subsequently the bus missing the other end of the gap. Had this scene been filmed with a bus really physically jumping the gap, we would be in tears, knowing that Keanu Reeves and Sandra Bullock never would have survived the jump, which would mean we would never get The Matrix, The Proposal, The Heat, or Gravity.
Cue our next movie – Mac and Me, a fully-featured McDonald™’s sponsorship film released back in 1988. Considered by none to be a necessary spiritual successor to E.T. the Extra-Terrestrial, Mac and Me is without a doubt a delightful watch. In a certain Academy-award deserving scene, our main wheelchair-bound character Eric Cruise (played by Jade Calegory) spots the visiting alien outside his home and tries to chase after him. Instead, Eric loses control of his wheelchair and begins to quickly descend down a hill. He then reaches the end of the hill, and unfortunately the beginning of a sharp cliff. Eric flies off the cliff and falls down to the lake below, where more Academy-award deserving acting continues.
Hold the phone though – we see the angle of the hill in one shot, the width of the lake in another, and in the falling scene, Eric is dropping straight down? That’s not quite right. Had Eric really continued his descent off the hill and down the ravine, his path of action would have been in a parabolic arc, due to his high inertia (from his high speed). Realistically, Eric would not have landed in the lake; rather, his parabolic path would have lead him into the rocks on the far side of the ravine. The filmmakers wouldn’t have the kindness to end Eric’s suffering early, and they knew they couldn’t end the film without getting to the McDonald™’s birthday party scene. Thus, we are gifted with this iconic falling scene, forever locked in history.
We are now at our final movie, and final scene, to be analyzed. Kung Fury, an independent short film released in 2015, is without doubt, the coolest martial-arts cyberpunk movie released that year. Regardless of how much I encourage everyone to watch this movie, it certainly has select scenes that some would say “stretch” the rules of reality.
In an early character backstory-building scene, our main hero and city cop Kung Fury loses his partner to a sudden ninja attack. In a series of lightning and cobra strikes, Kung Fury is gifted with the power of kung fu, and proceeds to smack the living daylights out of the enemy ninja. Specifically, Kung Fury kicks the ninja into the air, then jumps up to follow the ninja’s ascent. A second shot shows Kung Fury approach the ninja in mid-air, kicking them downwards, and continues flying up into the air. The final shot of the scene shows the ninja landing on an appropriately gas-filled tanker truck, causing it to explode, while Kung Fury lands in the foreground in an impressive classic Jean-Claude Van Damme split pose.
I will come out and say that if this scene were portrayed realistically, there would be many, many things that could not and would not happen as shown in the film. Putting that aside and nitpicking just this one scene however, we can assume that Kung Fury has an impressive jumping and kicking ability. Still, no highly skilled jumper could ever jump in the air, kick another person to the ground, and continue ascending into the air without a natural parabolic path of action. It’s just not fathomable. We see no realistic deceleration in the ascent, no acceleration in the descent, and no peak/apex of Kung Fury’s arc. Kung Fury’s weight should have at least slowed him to a stop at some given height, and then descended and accelerated due to gravity. Here's the full scene:
To conclude, in looking at all three of these films and their erroneous scenes, some of them we can forgive in the name of good, fun film. In the effort to provide a thrilling moment, to continue the plot, or to give a good laugh, sometimes forgoing science and physics is necessary in telling a good story. Had all of these films been shot with realistic physics shown, each moving object should have visually indicated a parabolic path of action. However, we are given some scenes that look a little funny, or are actually really funny, but all are undeniably entertaining.