Based on the first of J.K. Rowling's Harry Potter novels, Harry Potter and the Sorcerer's Stone follows the story of the young Harry Potter and the magical events that unfold around him. The much-anticipated film was directed by Chris Columbus for Warner Brothers Pictures and stars Robbie Coltrane, Richard Harris, John Hurt and Dame Maggie Smith.
Due to the nature of the story and the fantastical characters involved – such as giants, goblins and dragons – the novel required a whole host of visual effects in order to bring it to life on screen. The Moving Picture Company was asked to create 85 digital visual effects shots for the film. MPC's key effects include the shack on the rocks, the Chocolate Frog, the Golden Snitch and the screaming book. In addition to the special effects, MPC also used pioneering camera tracking technology, implemented for the first time in Europe, on Harry Potter.
When the Dursleys – Harry's aunt and Uncle – flee with Harry to a dilapidated shack, located on a rocky outcrop way out to sea, a storm is raging. MPC created a 3D hut for this scene and tracked the digital structure into a daylit helicopter aerial plate, colour corrected to a dark and stormy night. CG Supervisor and Lead Animator Chas Jarrett built the hut, based on concept art and photo-textures of Cotswold stone constructions. A digitally manipulated sky was added, with rolling clouds and lightening as well as CG rain and CG spray from the waves. A wet and glistening texture was then applied to the hut, before the shot was put together by 2D Supervisor, Greg Salter, in Cineon.
MPC also created the magical "Chocolate Frog," which comes to life after Harry unwraps it, jumping onto the train window and out of the train. Chas Jarrett modeled the Frog in 3D in Maya. Various chocolate textures were explored, the final one being based on a chocolate Easter bunny, very smooth with a slight sheen.
Another key sequence in the film is when Madam Hooch explains the rules of Quidditch, a magical aerial sports game for wizards, where the riders are on broomsticks and the aim is to capture the Snitch, (a darting, winged brass orb). MPC created a completely CG Snitch in Maya, which sprouts "humming" wings and flies about. A reflection of the Snitch was also added to Harry's glasses – to make the illusion complete. Later in the story, Harry is looking for information about his family history when a library book literally comes to life and a screaming face jumps out at him through the page. MPC took a greenscreen plate of the book, added in the pages and then created a 3D face. The face was then animated to scream violently and lurch through the page, tracked to the book in Maya.
The "Devil's Snare" – a plant with snakelike tendrils which comes to life and wraps itself around Harry, Hermione and Ron – was treated by MPC to add atmosphere to the scene and make the plant appear more sinister. The tendrils were rotoscoped and glistening highlights were added to provide a wet, slimy look. All of the shots were treated in Commotion and Shake.
MPC also created many other visual effects - including the CG smoke in the Remembrall, (a small crystal ball), several owl shots, where CG letters were required and countless wand effects. Throughout the film many spells are cast and MPC created numerous sparkling wand effects for these, each one adapted to reflect the type of spell. One example is the flashback sequence, when Hagrid recounts to Harry how his parents were killed. These effects were generated using 2D tools, creating mixtures of particle animation and adding 2D light effects and texture. When Neville is looking for a fight, Harry also casts a spell and freezes him. 2D manipulation was used in Cineon and Shake to create the cold, icy air effect that is expelled from the wand.
MPC's Camera Tracking System
MPC developed a camera tracking system in conjunction with BBC Resources. This system eliminates the need for post production tracking and marker removal and proved to be a great success on Harry Potter… A trademark shot in Harry Potter is the approach to Hogwarts, the school of witchcraft and wizardry. Hagrid and the children are approaching the castle at night by boat across a great lake, when the castle and its turrets come into view. Using an on-set camera tracking system of overhead retro-reflective markers and infrared motion capture reflectors, MPC's CG technical director, Peter Muyzers, interlocked the Super Technocrane move with a 3D Maya model of the Hogwarts miniature. This enabled the crew to previsualize and frame shots which showed the turrets and towers of Hogwarts on the greenscreen set, (against which the live action plate with Hagrid and the children in boats were filmed).
This camera tracking system is also used in the Forbidden Forest sequence for a very complex camera move, when Harry meets the centaur, Firenze. The live action with Harry, combined with the interaction with the CG centaur, necessitated previsualization. MPC facilitated this by installing 350 tracking markers above the forest set, reflecting infrared signals from the camera. A 3D model of the forest was built using the data produced and the crew was able to see the movements of the centaur, in real time, composited with the actor on the video playback.
Warner Bros Pictures