Julian Johnson-Mortimer has been working with the crew at CineVision for some time now. This small, boutique shop has now had a chance to create dinosaurs and giant sea creatures for a National Geographic IMAX production. Bringing dinosaurs to life in 3D has its highs and lows, and requires steady, whole-team coordination.
Johnson-Mortimer's work has appeared in Ballistic Publishing's EXPOSÉ 2 and EXPOSÉ 4. His images also appear in the original EXPOSÉ book, produced in 2003.
Working at CineVision, the crew did about 85 shots for the ‘Sea Monsters IMAX’ show. The majority of these were living underwater and a handful tramped about on land. The above ground shots featured a Gorgosaurus, which was a 30 foot high relative of the Tyranosaurus Rex, as well as a family of Pteranodons, a featherless flying dinosaurs with a 25 foot wingspan.
The underwater shots ranged from deep water environments for the Tylosaur fight sequence, to clearer, warmer, shallow sequences featuring the Dolichorhynchops, affectionately called ‘Dollys,’ Styxosaurus and a variety of prehistoric fish species.
Click the image to play the Promotional reel for Sea Monsters IMAX.
Scientifically correct
It was a challenge for the CineVision team, getting the animations approved at times. “There was a panel of expert palaeontologists who supplied us with joint limit data and limb motion diagrams derived from fossils,” says Julian Johnson-Mortimer, working as modeler and texturer. “From there, we developed animated swim cycles that satisfied the experts. However, the animators were animating action shots that were supposed to convey some drama and tell a story. When creatures fight, play and die, the animator’s instinct is to do whatever is necessary to make the body shapes flow with rhythm in the frame, including taking some joints a little past their scientific limits.” What they found was that swim cycles tend to lose their usefulness when that happens. So each and every animation had to be given a lengthy review and approval process where they were signed off by the director and the panel of eleven experts.
Creature challenges
Robin Aristorenas, VFX Supervisor and Director at CineVision, talks about the live action water surface. “There were sweeping camera moves in a few shots and tracking the choppy surface was near impossible. When creatures were close to the camera it didn’t matter too much if the move was interpreted as a track or a nodal pan,” says Aristorenas, “but when we added elements that filled the space, right up to the surface, such as fish and plankton, it became very obvious where the camera really was. Even though the water was moving, any slight slip in the track became obvious. As a result, in one shot we had to stealthily replace the plate with a CG generated water surface.”
Also, lens measurements had to be taken with a pinch of salt. The refractive index of water meant that lens values on the CG cameras had to be offset from the real lens measurements. Objects appeared to have been shot with a longer lens.
“The underwater environment could be forgiving in other ways,” says Julian Mann, the Head of R&D at CineVision. “Gravity is a big deal when animating creatures on land. Slight errors of acceleration or balance stand out because our brains are so tuned to its affects, and because we are so much heavier than air. But underwater, we didn’t need to think about gravity except when animating bubbles. As it turns out, drag is the force to be reckoned with underwater. We noticed this early on with our Tylosaur animations. Sea creatures are generally shaped like missiles in order to reduce drag, and when they move, the most efficient way is to carve a channel through the water with their body following the path. When creatures with eel like tails propel themselves, there is a clear forward motion as a result of the sine action at the tail. In fact the sine motion in fish has evolved to minimize work, by making sure every part of the tail is pushing against the water all the time, opposite to the direction of travel. If the animation breaks these rules and the creature moves sideways or the sine wave doesn’t move fast enough to match the forward motion, then the audience can spot something is wrong just as they spot gravity violations above water.”
Stereo 3D
Working with stereo 3D was a big challenge and a big learning experience for the Cinevision crew. Production is fundamentally different to traditional CG, because you are working with the space in the theatre as opposed to just the screen. Julian Mann found himself talking about the position of creatures in terms of how many rows away they are. While this sounds obvious, it was very difficult to appreciate how many areas of the work were affected.
“Well, to begin with,” he explains, “the stereo image is a more immersive experience for the audience, and in many cases when you violate certain guidelines or make stereo errors, you seriously interfere with their perception and sense of balance. This can cause headaches and nausea!”
As an example, eye muscles can relax to focus on something in the distance faster than they can converge on something close up. So animators need to be aware of this during choreography and avoid bringing characters forward too fast, or bringing them into frame only a few feet away. A related problem is letting a character break the edge of frame at two different depths. If it’s head breaks the bottom of frame at five feet away and its tail breaks the side at 25 feet away, the viewer will get conflicting perceptions about where the image plane is, and again, they may begin to feel sick.
Working in stereo also means everything must fit within the real limits of the set, in CineVision’s case between the sea surface and the seabed. However, as a shot progresses, everyone is thinking about composition and action, and not stereo integrity. Creatures get moved for artistic reasons and end up swimming above the surface or below the seabed. “We built up a number of techniques to deal with this,” explains Mann, “including warping the plates to push the seabed down, moving the CG left and right cameras further apart to bring the CG closer, replacing parts of the plates with CG and in some cases re-projecting the plates onto 3D models and re-rendering. We built a stereo screening room before we started, so fortunately we were able to spot these problems early and nip them in the bud.”
Depth Passes
Finally, working in stereo IMAX means rendering two 4k images for every frame. "Apart from the obvious burden on storage, the network and the render farm, it also means compositors are working with a different set of constraints," explains Senior Compositor, Chris Panton. "Depth passes are needed for just about everything. Anything done in comp for the left eye has to be done for the right and matched in stereo, so hand tweaks are not an option. A mere tweek can’t patch things up and rotoscoping is out of the question. If it’s not key-able or rendered separately, you can’t isolate it. Some interesting stereo effects can be achieved by using stereo plates as the source. For example ‘god-rays’ can be extruded down from the bright spots of both the left and right sea surface elements. The resulting shafts of light are in 3D and help reinforce the illusion of depth. However, as they are separate elements, we can use depth passes from the CG creatures to occlude them in places too."
A fun challenge was breaking all the established ways of doing VFX every step of the way, so the crew tried an experiment with Sea Monsters. “The clients, Sean and Jack were in LA and the plan was that they would stay there,” VFX Supervisor Robin Aristorenas describes. “So we decided early on to work without boundaries. We found talented people around the world, rather than be limited to who was available in London; we set up online shot tracking, dailies and asset management; and we made a conscious decision to have direct communication between the director and the people working on the shots and we decided to have no producer, just coordinators. Too often in visual effects, messages get passed down a chain of supervisors and producers before getting to the artists and the result is that all the life gets filtered out of the system. We wanted to make everyone part of the network, where informal conversations could spring up as necessary. Skype made this possible and we relied heavily on it throughout. There would be times when one of us in London would be talking to an animator in Brisbane about a shot and if Sean’s icon said online, one of us could just drag it into the conversation and a conference call would start. We think the experiment paid off. We learned a lot about working with crew distributed over four continents and definitely want to push this way of working on our next project.”
Artificial life
For the bait ball scenes in the sequence, artificial life simulation software was written to make the fish schooling behaviour as realistic as possible. “Each fish was made aware of its neighbours, the environment and the other creatures in the scene, and equipped with a stack of sensors to measure these objects in different ways,” Julian Johnson-Mortimer explains. “For example, in a typical simulation, a fish would receive signals telling it how to align its speed with its neighbours, how to avoid collisions with them in the future, how to move to the centre of its neighbours and be less exposed, and how to avoid Tylosaurs with the least effort. These signals arrive at the fish’s brain but only the most important ones are acted on. If a Tylosaur arrives the fish thinks, “forget staying aligned and just get out of here quick.”
In addition there are constraints on how fast the fish can turn and accelerate, and the angle at which it can swim. The result, when thousands of fish are interacting with each other is sometimes very beautiful, but very unpredictable emergent behaviour. And not just unpredictable; this can be difficult to tweak for large scenes as the behaviour can change qualitatively if the number of fish changes, just as it would in a real bait ball. “So a piece of software we wrote late in the day was a tool to mutate the simulation parameters and distribute all the variant simulations to the render farm,” says Julian. “It then collected the caches and created hardware renders. When we started sending Sean 12 or 16 variations at a time, the approvals process went much more smoothly. The idea of batch mutating simulations is something we intend to develop further and use for physics simulations and renders too. We also wrote a fluid simulator for bubbles and turbulent motion that runs on the GPU. The results are similar to Maya’s fluids, but it runs about eight times as fast.”
CineVision visual effects
the artists
Robin Aristorenas: Helmsman
Chris Panton: Stereo Effects Oceanographer
Julian Mann: Artificial Life Developer
Julian Johnson Mortimer: Senior Paleoanatomist
Natalija Lomakina: Stereo Image Integrity Technician
Benjamin Folkman: Paleo kinematicist
Aaron Briggs: Paleo kinematicist
Gang Trinh: Paleo kinematicist
Olivier Junquet: Artificial Phenomenon Artist / TD
Fredrik Sundqvist: Artificial Phenomenon Artist / TD
Joel Anderson: Paleo Biomechanic
Skirma Jakaite: Paleo-block Kinematicist
Justas Giedraitis: Camera Integrity Technician
Zhang Jian: Shading & Rendering Architecture
Paul Brannan: Sub-aqua environmentalist
Mathew Cooling: Paleo anatomist
Alex Oliveira: Paleo anatomist
Tony Naqvi: Chaos Wrangler
Mushaf Khan: Entropy Wrangler
production management
Raminta Poskute: Resource Harmonizer
Byung-Joon Kil-Lim: Resource Harmonizer
Dainius Dapkevicius: Digital Asset Wrangler
Jeff Allen: Studio Principal Chef
Allison Hughes: Studio Guardian
Raquel Santa Engracia: Studio Guardian
