Pixar's latest film UP opens in the UK today. It tells the story of a retired widower called Carl who uproots his house and flies it to Venezuela, suspended from a canopy of helium balloons.
During the five years the film was in production, Pixar employed new rigging, animation, shading and rendering techniques to overcome the challenges the movie brought to the table.
Like the house in the film, the technology to create UP was anything but a light load. The challenges included defining intricate rigging and simulation to reproduce the balloons convincingly, and inventing a clever workaround to overcome the inherent difficulty of rendering iridescent feathers.
NEW PIXAR: UP is the latest movie from the CGI giant to grace our screens
The solution for Pixar was to develop new shading techniques that would push its industry-standard RenderMan rendering software to new heights. Supervising technical director Steve May explains: "The balloons were the biggest problem. Managing the complexity of the balloon canopy required some new techniques."
The solution was to use a physics-based simulation. In September 2007, FX technical directors Jon Reisch and Eric Froemling were tasked with transforming the canopy from the static model it was at that stage to a secondary character in its own right. "We needed to figure out a way to either simulate or animate the balloons. It required a massive effort to rewrite our rigid body pipeline from the ground up," says Reisch.
Reisch and Froemling started with the shape of the canopy, and a balloon was instanced on each of the points within that defined shape. Froemling set up the Open Dynamics Engine rigid body pipeline and wrote a Python layer on top of the ODE.
Then the Python procedural setup was abstracted into nodes in a Maya interface designed by Reisch. This enabled them to manage the amount of bounciness the balloons would have when they collided, and to vary the sizes of the individual balloons depending on where they were in the canopy.
TIME CONSUMING: Painstaking modelling has created a very impressive effect
The final balloon count was 10,2