The VFX house created a city of gold and a secret lake in Mount Rushmore for Nicolas Cage to explore in National Treasure: Book of Secrets – but the work didn’t end there.


Asylum has reprised its role as key visual-effects facility on the Bruckheimer’s National Treasure, creating more than 500 VFX shots for the action adventure Book of Secrets.

National Treasure: Book of Secrets sees Nicolas Cage return as treasure hunter Ben Gates, on a mission to discover the truth behind the assassination of Abraham Lincoln, by uncovering the mystery within the 18 pages missing from assassin John Wilkes Booth’s diary.

This journey across America to Paris and London and back again leads Ben and his team to surprising revelations, and also puts them on the trail to some of the world’s most treasured secrets.

For Asylum, this meant visual-effects work that ran the gamut from relatively simple wire removal to designing and making full-blown CG environments.

“We were truly excited to be asked to work on the second film,” says Kathy Chasen-Hay, visual-effects supervisor at Asylum.

“The first National Treasure was a great experience for us. It’s also a compliment as well as a challenge when a director wants to come back a second time.

"We wanted Jon Turteltaub to see how much Asylum had grown since the first National Treasure, and I feel we got the opportunity to show him on the second film.”

National Treasure: Book of Secrets was a particularly complicated project, explains Chasen-Hay, with multiple iterations of shots created as the needs of the production grew.

The Asylum team used a wide variety of techniques, including photo-real CG, matte painting, compositing and rotoscoping to create the effects. However, they aimed for subtle, realistic effects that wouldn’t distract the viewer from the plot.

“Hopefully, none of the visual effects bring attention to themselves and are obvious to the viewer,” she says. According to Chasen-Hay, as the film’s production was continually evolving, the original storyboards were not an accurate representation of any particular sequence.

Instead, the Asylum team worked closely with the film’s art department, receiving updated conceptual and architectural drawings on a regular basis.

“Things changed quickly,” recalls Chasen-Hay. With that in mind, Asylum began previsualization work on the Balance Chamber sequence through to the discovery of the underground City of Gold.


The previs team worked for about six weeks, tweaking and improving the sequence as directed by the production crew. “While this previs was by no means a definitive map of the sequences, it did provide a template for filming and helped to raise and answer questions that had not been considered at that point,” says Chasen-Hay.

Ayslum had to create several key CG environments for the film. Among the most technically challenging to create was a huge lake hidden by Mount Rushmore.

To create the lake, the team blended shots of Mount Rushmore with shots of nearby Sylvan Lake. As the two locations were actually 20 miles apart, matching the lighting in the shots was critical – as was environmental cleanup, which involved removing all signs of civilization from the shots including roads and the crew, and adding the rocky backs of the presidents’ heads.

“We were always aware of the challenges presented by the other CG sequences. However, flying over Mount Rushmore to reveal the lake beyond struck me as a deceptively difficult shot,” says Chasen-Hay.

“At first read, the task of hooking together helicopter footage from entirely different locations, and incorporating 3D and 2D elements, was daunting.

"Attempting to match pitch, roll rotation and lighting of the different locations shot from a helicopter, was going to be very difficult. Fortunately, the pilot was adept at recreating his flight path and in conjunction with the aerial DP, we were able to get plates that approximated the same movement.

"Careful tracking and compositing took us the rest of the way,” she says – adding that this was far from being the only difficult shot.

Another sequence inspired by the Giant’s Causeway – the famed rock formations in Northern Ireland – proved to be similarly challenging.

In the scene, Gates’ parents, separated from the rest of the explorer party, swing across a chasm to continue their journey to the centre of the earth. A small portion of the environment, featuring the octagonal rock spires unique to Giant’s Causeway, was built on each side of the soundstage with a rope-like vine hanging from the stage ceiling.

The sequence was shot against blue screen from two camera angles simultaneously, and the size-to-be-determined cave was added digitally.

The final sequence, however, was different to the original production concept, as Jon Turteltaub, the director, felt that the octagonal spires took the audience out of the movie.

So the Asylum team recreated the environment so it looked like it was in the same underground space as the other underground sequences.


The underground City of Gold proved the most labour-intensive sequence for the effects team. The scale of the city made it too large to be built physically on an existing soundstage.

So the production crew built only those parts of the set that came into direct contact with the characters, with the rest added digitally in post-production.

Referencing Mayan, Aztec and Mesoamerican architecture, sculpture and art, the Asylum team incorporated many different looks to create the underground city.

The fact that the plot stipulates that the metropolis is supposed to be constructed entirely of gold was a challenge. “Gold has many distinct qualities that depend upon lighting and surface characteristics. All of these things came into play for the City of Gold,” says Chasen-Hay.

“The City of Gold sequence was a tough compositing task,” Chasen-Hay continues. “Many passes of CG gold for set replacement were rendered, and the compositing team had to blend these elements on a per-shot basis yet create an overall continuity for the sequence.

"Adding multiple layers of CG water and water elements, as well as the gold passes, atmospherics, set extension and re-mapping of gold and stone surfaces, made the City of Gold an extremely complex compositing job.”

National Treasure 2 is a film that illustrates the value of good compositing she adds. For the large CG sequences, compositors were working with dozens of layers of plate photography, element photography and digital elements.

The Asylum team used Flame, Inferno and Shake for compositing, and Maya and Houdini for 3D modelling. “Our rotoscope and paint departments were also crucial to the success of the compositing,” says Chasen-Hay.

As characters had to be completely extracted from the filmed backgrounds and composited into full CG backgrounds, the post requirements included lots of rotoscoping of fine hair detail and motion blur.

“The compositors had to match lighting and blend plates together that were not initially intended as visual effects,” she explains.

“The Noble Bird sequence, for example, required the compositors to perfectly blend the digitally-created image of the bird onto plate photography in extreme close-up shots.”

Tracking was critical to the success of these shots as was extensive clean up of the sets. Overall, says Chasen-Hay the Asylum team had to bring many skills to this production, along with meeting and exceeding the expectations of the clients – all of which, she says, was rewarding.



The City of Gold was almost entirely created digitally, as it was far too large to be built on a soundstage. These images show the CG process.


All that glitters

Among the biggest challenges of the City of Gold sequence was lighting the city, which featured many different surface textures.

“Shiny gold, pitted gold, clean gold, dirty gold, smooth gold, and wet gold looks were all built so that the lighters and compositors could blend elements on a shot by shot basis.

On-set lighting was a starting point but, in many instances, it was necessary to override the look of the lighting in the plates to enhance the dark and cavernous look of the CG city,” says Chasen-Hay.



A balancing act for Asylum

For the Balance Chamber sequence, Asylum had to make the actors appear as if they were 80 feet above the ground, standing precariously on a tilting platform. It was one of the most complicated shots the team worked on, according to Kathy Chasen-Hay, visual effects supervisor at Asylum.

Not only did the team have to produce full 3D rock wall extensions, it had to build a replica of the platform in 3D so the rock, roll and pitch of the platform itself could be manipulated as well.

“Initially, we had to create the 80-foot deep pit surrounding the balance platform. But as filming progressed, the sequence grew and the needs of visual effects grew with it,” says Chasen-Hay.

“In order to achieve the desired atmosphere, interactive dust was needed for almost every shot. This called for the development of a pipeline for digital dust hits, foot stomps, flashlight beams and ambient atmospherics that needed to match the actions of the actors.

"An element shoot provided a library of dust elements, which the compositors could use as well as the custom, per-shot elements created with particle systems. The sequence also grew to include the destruction of the balance platform itself.”

A scale model was built at Kerner Optical in San Rafael. Asylum augmented this model with digital dust and debris to enhance the sense of scale, and extensive compositing to match lighting and seamlessly blend it into the sequence.

To increase the drama of the sequence Asylum was asked to recreate the platform surface as a digital model that could break apart as Nicolas Cage leaps to safety.

Getting this digital element to work convincingly with the plates was an animation, lighting and compositing challenge. As the sequence evolved, new shots were added to heighten the suspense.

Actors were shot on bluescreen and composited into digital versions of the set. Near the end of the sequence, an idol is rolled onto the platform to offset the tilt.

On the shoot, a stone idol prop was used which was then replaced in post with a gold idol. Asylum has to carefully track the gold idol to match the movement of the set piece, as well as match the lighting. A CG breaking ladder-rung and wire removal work helped to complete the sense of danger demanded by the sequence.



The Noble Bird scene required Asylum’s artists to blend a digital image onto plate photography, in extreme close-up.

CREDITS

Project: National Treasure: Book of Secrets
Client: Walt Disney Studios/Jerry Bruckheimer Films
Studio: Asylum, www.asylumfx.com
Software: Apple Shake, Autodesk Maya, Autodesk Flame, Autodesk Lustre, Side Effects Houdini