Behind the scenes of Hotel Transylvania 3D

Currently playing in cinemas nationwide, Hotel Transylvania 3D is Sony Picture's latest computer animated movie. Lead Stereoscopic Supervisor Von Williams describes some of the processes behind bringing famous horror characters out of the screen.

Genndy Tartakovsky's feature directorial debut tells a story of Dracula (voiced by Adam Sandler), who, as a hotelier, provides a sanctuary for the world's monsters (such as Frankenstein's monster, a Werewolf family and the Invisible Man), to take a rest from human civilisation. However, when a traveller named Jonathan visits unexpectedly, an over protective Dracula tries to protect his daughter Mavis from falling in love with him before it is too late.

Despite mixed reviews, the movie set a new box office opening weekend record, earning over £26 million in the US and Canada – the highest ever September opening weekend. As with most computer animated movies, has also been released in 3D. 2D to 3D box office ratio figures are not currently available but Sony will be hoping for a higher 3D box office achieved than the dismal 32% of Disney's Brave.

A RealD representative recently achknowledged this decline, saying "Animated family films are performing toward the lower end… This has been consistent for some time as we see more sensitivity with family films".

Von Williams was the Lead Stereo Supervisor for Hotel Transylvania, having previously served as a Stereographic Layout Artist on features such as Aardman's Arthur Christmas, Tim Burton's Alice in Wonderland and Cloudy with a Chance of Meatballs. It was his responsibility to produce a 3D movie that would encourage the crowds to dig a little deeper into their pockets for those 3D tickets.

Supervising a team of 5 stereoscopic controllers and 50 – 60 lighting artists, Von Williams had one year to produce the 3D version, a major challenge:

"One year of production makes it difficult, so a lot of the focus is on the 2D movie." he conceded.  "For other movies, we can really take our time on the 3D but with Hotel Transylvania, it was a really pushed schedule; We didn't have a lot of time to take things back and forth. Fortunately for me, when the movie was finished, I was completely happy and so were Sony."

You might be surprised to hear that two separate movies were produced at the same time – the 2D and 3D version. Von William's stereoscopic team started with a rough layout of the entire animation which included the cameras, environments and characters. This was used to create a depth script.

A depth script is what a stereoscopic team uses to plan the level of depth per scene, shot by shot. When an element pops out of the screen, it is known as negative parallax and when an element appears behind the scene, it is referred to as positive parallax. The difference between the most extreme positive and negative parallax is known as the depth budget.

Stereoscopic Supervisors like Von Williams have to judge early on what will satisfy a diverse audience:

"Persuading people to see a 3D movie is always a difficult challenge. You will get one third of the audience saying 3D gives them headaches; another third wanting more extreme 3D and another will say it is just right so you are trying to please all these groups." said Von Williams.  "With a movie like Hotel Transylvania, we are not pushing the 3D to the extreme.  Stereo can really adjust the emotion and the intensity of the film. If you want something more intense, we will increase the stereo. For more emotional moments, we might want to calm it down a little bit so that's how we are blocking out our depth script all the way."

There is a sequence where Dracula flies a table, chasing Jonathan through a hallway, Star Wars X-Wing style. The depth for this scene was increased to provide a greater perspective of the length of the hallway and generate fun theme park style excitement during the moment.

The team created Dracula's fantasy virtual hotel using Autodesk Maya – a high end software toolset used by animators on most big budget computer generated movies. Maya was used to create the 'second eye' on Hotel Transylvania and increase or decrease the depth of each shot. Compositing (bringing several layers together into one scene) was achieved using The Foundry's NUKE software and Pixar's RenderMan was deployed to render out the files.

Rendering is a processor and time demanding process that 'builds up' every frame of the movie as it will be seen in the theatre. Render farms are employed to speed up the process where hundreds of computers generate each part of the movie in parallel. This time is doubled for a 3D movie as each eye is rendered as a separate file.

Despite many headlines shouting the downfall of 3D movies, releasing a 3D version of a movie can still provide healthy returns, albeit not on the scale of the Avatar days. Estimations vary but 30% is regarded as the average increase in the cost of producing a 3D movie in comparison to a 2D movie.

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However, an animated movie like Hotel Transylvania, costs considerably less to release in 3D according to Von Williams, making the business case even more viable:

"Because we are creating the 2D and 3D version at the same time, the cost to the budget is minimal, approximately 3%. When the lighters render the elements for the left eye they also render the right eye at the same time. As soon as the 2D shot is approved they have everything that they need for the 3D version. There were some occasions when the 2D shot would get approved in the morning, and the 3D shot would be approved in the afternoon review".

Although the post conversion and re-release of other computer animated movies like Finding Nemo and The Lion King was very successful for Disney, unlike live action movies, conversion of CG movies from 2D to 3D is more expensive than producing an original 3D version.

Aside for increasing the sense of feeling of 'being there' and enhancing emotions such as sadness, claustrophobia and fear, Von Williams' role as Stereoscopic Supervisor included ensuring the 3D was comfortable for the audience. 3D does not work well during fast paced, quickly cut action sequences for a long period of time, so the 2D version of Hotel Transylvania was edited at a slower pace to allow for a successful 3D version. One of the first 3D movies of the digital age was The Polar Express. The motion capture computer animated movie was never intended to be screened in 3D but fortunately, director Robert Zemeckis edited his movies at a slower pace than average meaning the 3D worked.

Hotel Transylvania also uses 'floating windows'. To create 3D, the left and right images are slightly offset. This difference is usually seen at the edge of frame. For most shots that difference is cut off because what is rendered is slightly larger than what is seen on the screen. However, there are some shots where that separation is larger than what is covered by the mask and that is when floating windows are created.  You may not notice it but a small boarder is added to each side of the screen, blocking out the difference between the left and right eye. If you watch Hotel Transylvania 3D in the cinema, see if you can notice the floating windows!

But what about that initial moment when you sit down, place your cola drink in its holder and don those slightly smudged glasses – you can't stop thinking about the 3D right?

"The audience is going to be aware of the 3D in the first 10 or 15 minutes." agrees Von Williams. "But I feel that the audience are expecting to see 3D from the opening of the movie. The audience has just made a decision to pay extra money for the 3D experience. Also, most theatres run movie trailers before the film that are in 3D. Those trailers are trying to show how amazing the 3D will be in their film. So, the audience is already immersed into 3D before our film begins, and we have to deliver to their expectations."

Hotel Transylvania is currently playing in cinemas nationwide in 2D and 3D.

All images copyright and courtesy of Sony Pictures Animation.

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