"When the rangers exit into the North we see for the first time some idea of the sheer scale of the Wall," he continues. "This was created by matte painting to extend a physically snowed up area around the live action. Our aim was to create something that had a hint of man-made structure about it and had to appear completely insurmountable or unscalable as it was built to defend from the creatures of the North. The edge of the forest was introduced using stills of snowy pines and atmospheric mist and snow composited in to create depth and movement.

Winterfell itself is essentially a digital matte painting using some 2.5D with the towers that they decided early in planning would provide maximum scope for reusing the assets with minimal cost implication for producing variations of similar angles.

"The Red Keep lent itself to a 3D build. We took concept work as a template and rebuilt it. In texturing we needed to create a transition from the yellower stone of Malta to the red stone from which the castle's title is derived. It had to be grand and beautiful, imply wealth and power, be extraordinary to the world as we know it but at the same time not veer too far into the fantastical."

Another significant feature of the series is the Eyrie. This is an impenetrable fortress high up on a rock base. "We went through a number of iterations of the concept on this being one of the most fantastical pieces of the series," McInnes says. "There were several options considered as to how the access should work in conjunction with the practicalities and location of shooting the arrival of Catelyn and her entourage. Ultimately, we opted for them rounding a bend on the edge of a gorge where we see the Eyrie perched in the distance only accessible via a guarded rock arch bridge."

Game of Thrones is one of the earliest productions shot digitally with the Arri Alexa cameras. The VFX team was involved in establishing a workflow from acquisition to delivery and received copies of LUTs to use as a guide when lighting and compositing and to deliver cutting copy versions of VFX that would look similar to dailies. Their delivery was still ungraded LogC DPX to the DI so that it would match original camera media and had maximum latitude when it came to developing the final look of the show. McInnes says they were blown away by the results of keying and grading.

Maya and Nuke were the standard software at BlueBolt. The matte painters used Photo Shop and Mari. Mud Box was used for some additional finessing of the models and all rendering was done using 3Delight.

Coming up, McInnes promises fantastic-looking dragons, which will hatched in the final episode of the season, "Fire and Blood." "The one area we really took great care on [was] the dragons in episode 10. We insisted on storyboards, previs and a maquette in order to get the builds underway in advance, knowing the limited post schedule coming up."

Bill Desowitz is senior editor of AWN & VFXWorld.