Cinesite, as the main supplier of effects for Harry Potter & The Goblet of Fire, completed 230 digital effects shots, as well as building all the models and Directing the model unit. Cinesite's key sequences included major complex composites, a full CG owl - Hedwig, CG candles, CG butterflies, CG rain, CG snow, CG raven and a CG ferret that transforms to Malfoy. A magic wand effect with interactive clouds and lighting, size enhancements for various characters including Hagrid, full CG ceiling replacement for the magic ceiling to create an ice effect. Portrait shots with live action element treatment which is then tracked back into a plate with the person over the background for each two layer shot.

Many shots filmed in the Great Hall of Hogwarts required the addition of large crowds of candles, floating in formation. Candles were filmed on the tables where the actors were sitting, with one filmed in the extreme foreground for a shot where the camera passed close by; this was used as a reference for the creation of the computer generated candles. Cinesite effects artists filmed candle and flame elements themselves to create several additional models which gave an individual feel to each candle, with randomised characteristics.

In order to give a realistic impression of the great size of the half-Giant born Hagrid and Madame Olympe Maxime Cinesite completed various shots which involved resizing Robbie Coltrane and Frances de la Tour. Live action was often filmed with a chroma key frame in the space which Hagrid would occupy, serving both as tracking marker for the compositors and an eye-line reference for the actors. The tracking data from the live action was fed into the motion control unit, which recreated the camera move when filming the separate footage of Hagrid. The Hagrid element was then composited into the shots in a larger scale.

Mad Eyed Moody looses his temper with Malfoy (Tom Felton) transforming him into a Ferret, tossed around in mid air under the spell of Mad Eye. The ferret had to exactly match the practical ferret featuring in the sequence and was modelled in Maya based on stills of the real ferret, measurements and lighting reference from the shoot. The transformation is initiated when Malfoy is sent into a spin from Mad Eyes blast, rotating on the spot like a twister he drills down into the floor changing in a blur to the ferret - particle and practical elements were manipulated in inferno for the final effect. Both Malfoy and several of the ferrets were filmed back at Leavesden on motor driven turn tables against blue screen which was re-sped and repositioned to match the original Oxford shoot some months earlier.