Last May, Guy Williams has explained to us in details about the work of Weta Digital on IRON MAN 3. Now he talks about his work on THE HUNGER GAMES – CATCHING FIRE.
How did Weta Digital get involved on this show?
We have a great relationship with the VFX Supervisor on the show, Janek Sirrs. He called us up one day and asked if we could help him out with some creatures.
How was your collaboration with director Francis Lawrence?
Francis was great to work with. He kept us on point to make sure that we created a scene that flowed from calm to anxious with just the right timing and balance of each. He’s also a nice guy in general.
What was your feeling to work again with Production VFX Supervisor Janek Sirrs?
Janek is great. He has a great sense of humor and is fun to work with. He also has an amazing skill at pulling the right result out of people. He not only makes the work better, he makes you want to make it better.
What was their approach to the visual effects?
It had to be real. The key was to make a scene that served the story and flowed well in the cut. But critically, it had to feel real. All of the storytelling would be out the door if people were stuck trying to get past fake looking monkeys.
What was your role on this project?
I oversaw Weta Digital’s work on the show.
What has Weta Digital made on this movie?
We worked primarily on the Monkey attack sequence (although it would be more correct to say Baboon).
Did you create previz for the Monkey sequence?
No, by the time we came onto the show, there was already an excellent set of previs that had been created by Proof.
Can you explain some details about the monkeys creation and rigging?
The monkeys are a mix of a drill and a mandrill (both types of baboons). It is the body of a drill with the coloration and markings on the face of a mandrill. We built the model to match the design work and reference that had been created/gathered up to that point. We then used our in-house systems to add fur and also to add tissue/muscles. We had to modify our fur system to deal with wet fur (really wet, like dunked in the water wet).
How did you handle the animation?
Reference, reference, reference. We looked at as much reference of baboons as we could find to see not only how they moved across branches and uneven ground, but also to see how they acted. The ways they express agitation and anger was very important to get right so it felt like a real animal and not just good animation.
Can you tell us more about the fur creation?
We used our proprietary Fur system to put down a few grooms on the drill (main coat, under coat, facial hair…). The fur system can read parameters from the surface so we passed the shaders all sorts of info (from the color at the base of the hair to values that specify how much water that part of the surface has come into contact with). Our shader team worked hard to get the unique characteristics of baboon fur just right. The short undercoat has a softer downy kind of fur that is also very white whereas the top coat has coarse fur with a lot of color variation.
You can see the baboons at 0:54 sec.
How did you simulate the monkeys on-set and their interaction with characters and water?
For the on set portion, they used tried and tested techniques. They would throw a weighted bag into the water for a splash or have a performer in a suit for the actor to act to or wrestle with. These worked quite well. A lot of the specific water interaction with the kids and the monkeys was done later as CG fluid simulations.
Can you tell us more about the forest environment creation?
The forest location they had was excellent. There was a very limited need for us to replace plants. The rule of thumbs became that if a Monkey interacted with it, we would replace it in CG. Having said that, there were also a few shots that were completely digital. It made sense for us in those shots to replace everything so we could more easily control the camera to serve the shot.
How did you manage the vegetation animation and render?
We have a suit of tools dating all the way back to AVATAR for plant interaction. It has grown a lot since then but the idea remains that same. We use curves to simulate every part of the plant and then just let things collide naturally. As far as rendering goes, we use Renderman for all of our work. The jungle was lit with area lights and then indirect was used to move light around properly.
Have you adapted your pipeline for this show?
Not too much. We did add some hooks into the fur system for making it deal with being saturated to different degrees with water. We had the ability to have it super saturated, saturated and just wet (the fur would dry through these states over time). We also added the ability to make the fur read in a fluid field and move with it. The fur on the surface of the water would stick to the surface faithfully while the fur under the water would swim around in the fluid current.
What was the biggest challenge on this project and how did you achieve it?
Water and its interaction with the fur. We simulated the water to a very small feature size to get it to have the correct sense of scale. The feature size was smaller then a drop of water so we were able to get it all in one sim. This, in conjunction with the additions to the fur system, made it possible to put the monkeys and kids into digital water in a convincing manner.
Was there a shot or a sequence that prevented you from sleep?
There wasn’t really one. The project was challenging and had its fair share of speed bumps, but all in all, it went pretty smoothly.
What do you keep from this experience?
I was real pleased with how the monkeys turned out. The motion on them was excellent (thanks to our brilliant animation team and their supes, Eric Reynolds and Dan Barrett). Also, we had fun. The client was nice to deal with and the work was rewarding.
How long have you worked on this film?
4 months.
How many shots have you done?
85 shots.
What was the size of your team?
Around 200 people.
What is your next project?
Dah! I am afraid I can’t say at this time.
A big thanks for your time.
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© Vincent Frei – The Art of VFX – 2013
