VFX Jargon: What are Dynamics and Simulations

February 19, 2016

VFX Jargon is a column in which we analyze and break down words in the biz so you don’t have to. This week we chat to Lead FX TD, Andres Berkstein, about what exactly dynamics and simulations are, and how they help achieve reality. Previously we spoke to Harimander Khalsa, Digital Effects Supervisor at Shade VFX about what the word “photoreal” means.

You’re responsible for creating fire, water, explosions, blood and all sorts of other awesomeness. What is the biggest challenge creating those effects

Each one of those components is a world of technical complexities unto itself. Some have deeper levels of difficulty than others, but the true challenge will always be to deliver the effect that is best suited for the shot and show. For instance, with blood, the greatest challenge is making it look and feel real while keeping to the parameters the client is looking for. Some directors want the blood to be thicker and viscose, others are looking for something different. Thankfully, here at Shade we have developed FX rigs that help the artist focus on the performance and not have to worry about the technical aspect as much.

How do you describe the work you do to people that don’t work in the VFX industry?

That’s a tough one, it ranges. Sometimes a conversation starts where I need to say, “No, I did not get to hang out with Tom Cruise even though I worked on his movie!” But once we get over that, I explain the two main areas of VFX, Computer Graphics and Compositing. The first one being a 3D world space in the computer where we can create extensions for sets, add assets like cars, create characters or do dynamics. And the latter being the assembly of the 2D image that gets projected, so that all the elements feel integrated with one another. From there, if I still haven’t confused people, I jump into explaining how the dynamics side of it works; how we use different types of software designed to recreate every material state and property from the real world and we apply them to simulate elements that need to have a specific performance for shots in a movie. Examples of those would be explosions, fire, smoke, destruction and water, just to name a few.

In the world of VFX, what does “dynamics and simulations” mean?

Dynamics is also commonly referred to as FX Animation. This is because it’s a discipline where we animate objects through controlled forces, which we call ‘fields’ in our industry. The clearest example of these forces would be gravity. Animations take place in a virtual world inside the computer software and in order for these forces to interact and move objects we have ‘solvers’, which are basically mathematical code that intends to control the virtual world in the same way the real world behaves. There are many types of solvers, depending on what effect we want to achieve; fluid solvers are based on fluid dynamics, for instance. Solvers take in different parameters depending on what type of effect we want to achieve. For instance, if we where to go into a destruction scenario, we would have to assign things like mass, friction and angular velocity to the objects, so that when the forces are applied they can interact accordingly.

What’s your favorite sequence you’ve created as Lead FX TD at Shade, and why?

There are some sequences I really like. We did the suit building for the upcoming Max Steel movie and that was a lot of fun, but my favorite is some really cool destruction we created for an upcoming episode of Black Sails. I really liked working on that because it’s a very complex shot with so many layers, and it required every department in CG, from Modeling to Animation, to work together with FX very closely and at the end you can see the amazing work that came out of that collaboration.

Are there core concepts, elements or phenomena involved, or is every job completely different?

Definitely there are. Even though FX is a very broad department encompassing several types of effects, its main goal is to make things look as if they were governed by real life rules. As I mentioned above, we use solvers that take in data that we as artists or TD’s use to control the world in which the simulations are taking place. The technical aspect of this is based in math, so we have constants as to how things work and how we do things, like for instance, using the velocity vector to propagate information from one solver to another. These workflows lay a ground floor from where we can build tools or rigs to control the simulations and give the FX artist time to focus on the artistry of the shot, which in turn has its own core concepts of style and aesthetic that are a constant to filmmaking.