CGSociety

Lagoa released in Autodesk Softimage 2011.5.
Hear from the inventor, Thiago Costa of Lagoa Technologies.

Lagoa Liquids in action in a screenshot from Autodesk Softimage 2011.5.

CGSociety :: Technology Focus
14 October 2010, by Paul Hellard

During IBC in Amsterdam when the Autodesk Softimage 2011 Subscription Advantage Pack software was publicized, it was also announced that the Lagoa Multiphysics simulation technology would be brought into the Softimage workflow. Thiago Costa, inventor of the Lagoa solver, has come a long way from the streets of southern Brazil. In his home town there were beaches and fishing boats, but no web, so he says he figured out lots of things by himself. By his own admission, he "learned how to make silly things happen on the computer".

After more than two years in development, Thiago Costa has unveiled Lagoa Multiphysics, an exciting feature addition to Autodesk Softimage, the first application he targeted for his new solver.

Thiago has always been intrigued about the technology of arts. He enjoyed the mix of both disciplines and made his career lean in this direction.
He moved through photography, video, advertising and eventually moved to the west coast of the US, working with CafeFX on fluid motion on films like G.I. Joe: The Rise of Cobra as a lead effects artist. "There I experimented with physics to do facial deformation rigs and lead the other artists doing their shots," Thiago says. "I could then take some distance from visual accuracy at that point, and focused on the mechanics of things rather than trying to please the eye and please the numbers.

The Brazilian became really interested in this subject and started to imagine things at a molecular level. Working out how they behave to create the motion that was big enough for human eyes to see. "That was enough for me to spend months and nights experimenting with tools that had physics behaviors. I studied the language of Mathematics and read a lot," he said. "I had a good knowledge of physics and geometry; it wasn't like falling from the sky into my head, but more like finally embracing the language."

After the US, Thiago moved to Montreal where he now lives. "Learning French sounded interesting, so why not," were his thoughts.

Lagoa Multiphysics Engine 1.0 video

Lagoa Video
"Lagoa gives you freedom to imagine," explains Thiago. "When you watch the video you see things that move realistically, but you can’t pinpoint what the substance is. In the first sequence there’s a block falling on the ground and it’s just falling and flowing. A lot of people say it’s dirt, others say it’s water, some say it looks like an object fracturing or charcoal. It just looks like many things because it is many things at the same time."

"In my first video, I was modeling elasto-plastic behavior, inelastic collisions, and something for incompressibility distribution. When the system breaks into smaller parts the coupling of these systems makes a whole subset of motion arise naturally," he continues. "That was an early version of the solver and was all written in C++ and output as cached files. Later, the solver got more compartmentalized so it could be assembled in different ways in a 3D application. Since you only need a subset of what's implemented in Lagoa, it's better to have it as an open framework that can be customized so users will be able to expand on it as they need."

"When you write down your equations, you realize what's overlapping and you can start to think whether it is better to keep things in memory or to compute it again. Sometimes it's faster to compute it again depending on the platform that you are trying to run it in."

Thiago started by implementing Smoothed Particle Hydrodynamics solvers. His first introduction was from a paper by who was very helpful in guiding Thiago in simplifying the standard formulations.

"The funny thing is Simon uses a very simple technique that allows a very stable surface tension model to be built into a pressure algorithm. After many discussions with Simon about my algorithm, I was inspired to simplify my own equations in the same way. Later on when Lagoa was mature enough, I had a few simulations to show, so I brought Simon to my studio and he was impressed. I expanded a lot on what he had proposed initially and it was motivating to show early tests of Lagoa to researchers such as (who saw a very alpha version) and received positive feedback. That made me believe I was doing something right. "

Fulfilling needs
"At the end of the day, as much as an artist wants to paint a photoreal splash of liquid, and a programmer wants to write liquid simulation software, they have to agree they are both looking to do the exact same thing. It’s just a different challenge but if you can talk both languages, why not? I got more serious about coding when I started Lagoa."

In fact there’s not one equation that solves all the physics phenomena in the world so one has to be used many ways to try to solve many things. A lot of researchers get specialized on one thing, and others try to unify it. Thiago's challenge was to unify a few models and make them useable rather than some obscure scientific tool.

The Lagoa solver can turn a cloth into a liquid. In other simulation software like RealFlow there are entire solvers just set up for cloth. Others set up for the depiction of water. In Lagoa, the same solver that solves the liquids can solve cloth. There is not any difference between them. This makes the software very powerful and extensible. You can attach all kinds of solvers in the back-end or a TD could create a skin deformation tool based on all the computational physics that are already available in the system.

Research
Research about grains might never explain anything about water and might use another formulation that does liquids to try to explain how water and grains mix.

So Thiago had to go a bit deeper. His work had a lot to do with generalizing a few of those models and finding their overlaps. "If you study the movement of 'cloth', 'grain' or 'liquid', you will find that their mechanics are quite similar," Thiago explains. "What I was aiming for was a tool that could model many different physics phenomena and the most fitting name for that was Multiphysics since it uses multiple physics models under the same model. You then create a new problem which is the interface between those materials. So at some point you've got to let go of academic research and do your own experiments, otherwise you just spend time scratching your head trying to add a feature to something that was never planned to have it."

"What’s appealing about ICE is that it’s super fast to get something prototyped and working. If you only using C++ there's all the 'compile and run' steps that you can skip in ICE. It takes much more time to do the same thing in another application."

More research
"The most unique feature on Lagoa is probably the way pressure is solved across the whole simulation domain," Thiago explains. "Mapping regions of low and high pressure to distribute the volume and giving back an intersection-free velocity field in only one step that suits all media, took a long time to develop. What matters to me is not the equations people arrive at, but rather why and how it moves and what the physics explanations are behind it."

"There are a lot of papers out there that are not going to tell you anything you don't know already, but they might have a hint of research that matches with something else you have in mind. So it's worth reading all of them, but I've found that sometimes by doing my own visual experiments and designing equations on my own, I arrive at the same conclusions."

The name - Lagoa
"I’m from Brazil and Portuguese is my first language so was important for me to have a name that honors my origins somehow. Lagoa means 'small lake' in Portuguese and it’s also the name of a neighborhood I lived in Rio de Janeiro. I chose the word Multiphysics because of the formulation for physics, which are too specific sometimes, and some people have already developed SPH frameworks, while others have developed rigid body frameworks, fracturing tools, cloth tools, etc."

Softimage ICE
Thiago Costa has used Softimage for a long time and knows a lot of Softimage users. In fact, ICE was his primary research platform. "ICE is a great API for implementing solvers and you can keep developing externally but run into an application that's immediately useful for production." Being a beta tester for Softimage for a long time, he also got to know well a lot of developers as well as product management, who proved very helpful."

Beginnings
His high school chemistry teacher and geometry teacher told Thiago that he'd had enough with school and should do something else. "At that point I was already programming stuff but was having more fun with visual stuff. I was driven by things that were visually interesting," he says. "I got to work at many places in Brazil, I grew up in the south and lived in Rio for five years. I worked at the major TV channel and advertising industry and a little bit in film productions in Brazil. I kept in contact with a lot of people, a lot of Brazilian artists and people that inspired me as I was transitioning from art to programming."

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