Particle animation: isn’t that something to do with physics?

If you’re wondering how particle animations work, going back to their beginnings is a pretty good start. In 1982 cinema viewers were treated to one of the first on-screen particle simulations in Star Trek: Wrath of Khan. Kirk, Spock and Dr McCoy watch as one Dr Carol Marcus explains the genesis project in a pre-recorded presentation. The trio see the Genesis Demo as a simulation on a computer. In the magazine American Cinematographer, Alvy Ray Smith described the 67 second sequence as created from several different computer-generated components, including the particle animation of fire spreading across a planet created from code written by Bill Reeves. Beginning with a projectile (the genesis torpedo) speeding toward and hitting the planet surface, the sequence continues with a fire, initially at the point of explosion before spreading out. Immediately, other CG elements populate the imagery – fractal mountains, lakes, oceans of water, and finally an atmosphere looking like that of Earth complete the evolution of the new planet from its fiery origins.

The Genesis Demo set the foundation for the thirty-five years between now and then. Bill Reeves’ 1983 article ‘Particle Systems,’ is a great place for starting to get to grips with particle animation. Reeves writes in a very informative way, and you don’t need to be able to make sense of the equations to gain some insight into his software. As he explains, when creating a shape using particles, its dimensions are given by the volume of a particle cloud, meaning the specific boundaries of it’s shape are not fully defined (he uses the word determined). Because a particle cloud is continuously generated, objects created in this way are dynamic and fluid, as opposed to static. This makes particle animation ideal for ‘fuzzy systems’: smoke, fire, clouds, moving water, sparks, fog, snow, and dust. For particles animating the spread of fire across a planet, their motions and transformations are tied to the solution of equations. These form the basis of algorithms that mathematically model the physics of natural phenomena, water crashing down from a height, the swirl of snow or smoke. Reeves included a randomised (stochastic) input that controlled the emission of the particles, and the software also granted a model builder some control over how the physics of the system would play out. As Reeves explains it: ‘To control the shape, appearance, and dynamics of the particles within a particle system, the model designer has access to a set of parameters. Stochastic processes that randomly select each particle’s appearance and movement are constrained by these parameters.’ The Genesis Demo wasn’t the first time that particle animation was used for things like smoke and galaxies, but Reeves introduced randomness and a degree of creative control to the process.

Still: particle animation of fire used in the Genesis Demo

In the thirty five years since Star Trek: Wrath of Khan, particle animation software has developed, with packages like Houdini, Maya’s Particles and Blender widely used in visual effects for cinema, animation and games. These increasingly sophisticated systems still rely on solving equations to simulate an object such as water in Moana or sand in Mad Max: Fury Road’s toxic storm. Simulations are often widely applauded for their degrees of accuracy in the movements and transformations of particles. At the same time, developers constantly aim to enhance the control available to visual effects artists. While particle animation algorithms are designed around physics, visual effects are not just about simulating reality. Often, something dramatic is what’s needed, and that is where artistic control comes in. The challenge for software developers is too make their packages open to artistic control. The challenge for people interested in cultural politics is to understand the ways and the extent to which simulations are not altogether real.

William T. Reeves (1983) ‘Particle Systems: Technique for Modelling a Class of Fuzzy Objects.’ Computer Graphics 17 (3) 359-376.

Entangling with The Pirates! In an Adventure with Scientists!

I’m beginning a piece on the Aardman animation The Pirates! In an Adventure with Scientists! or Pirates! Band of Misfits, as it is known in the US. The Pirates!, though primarily a hand-crafted stop-motion animation, uses a lot of CGI, with some 80% of shots involving a digital touch too. Where the figures are stop-motion puppets crafted from clay (or silicon or even foam), and the sets are physically built in the Aardman studio in Bristol, a lot of details were removed using digital tools (rigs used for the complex acrobatics of action scenes, joins between the 3D printed and hand-sculpted elements of the figures’ faces, as well as glitches from dead pixels in the cameras). The partying pirate crowd and rows of seated scientists were populated with digital extras, Blood Island was digitally enhanced and the roofs of London sometimes digitally finished. From this list it’s clear that in The Pirates! physical and digital elements are consistently intertwined and nothing is ever quite as it seems on the surface.

So far so good, but where to go with this? Well, the idea of entanglement is something I’ve been wanting to explore more for a while. My starting point is Tim Ingold who has a fascinating way of describing how objects are different to things. Where objects are already described, solidified into categories, things are more fluid, knots of constituent threads trailing beyond the surface boundaries of a thing and becoming caught up with other threads. Things are entangled, ‘a meshwork of interwoven lines of growth and movement,’ changeable configurations of knots and threads.

Ingold is talking about things generally, and grounds his more abstract thinking with examples of things in the world, such as kites or trees. Kites are one thing when constructed inside a room, and become another when taken outside to fly or not, as the case may be. As I read about ‘kites-in-the-air,’ I think I grasp the point about things but find it hard not to let it slip again when musing about the possibilities the idea offers for moving image studies. Even so, Ingold’s description of things being entangled, of things having interwoven lines of growth and movement remains attractive when looking at how physical and digital elements are entwined in The Pirates!

curvy-pirateSurprisingly Curvaceous PirateThese very preliminary thoughts throw up an issue when using entanglement to think about entities in moving images already made. In one sense they are in keeping with a description of objects as completed works, already given categories, and often thought backwards – traced back to the intentions of their makers. Take the Surprisingly Curvaceous Pirate, a cross dressed woman who seems to have either escaped everyone’s notice or whose obvious pretence simply goes unmentioned. Thought backwards, Surprisingly Curvaceous Pirate’s origins lie in the five novel series on whose stories The Pirates! is based, but taken to a different level in the animation with the curves of her body and patently fake beard all part of the joke. In contrast to thinking backwards, Ingold encourages a process of thinking forwards, of trying to anticipate what might emerge in what he calls a gathering together of the threads of life, and be attentive to all the goings on that come together as a thing is made.

How might this work for the Surprisingly Curvaceous Pirate, or anything else in The Pirates!? One of things that intrigues me about the animation is its playfulness around disguise. But instead of trying to settle on what something is or isn’t, I’m going to look beneath the surface, to the knotted strings that pull together. The Surprisingly Curvaceous Pirate’s face is never revealed, but all the knots are there. In the same way, even though the boundaries of digital and physical elements of the image might appear settled, there are many knots to unpick.