We're now more than halfway through the new series of Doctor Who, starring Peter Capaldi as the latest version of the time traveller. And whatever you think of the new plotlines, characters and monsters, there's no question that the visual effects are as creepily convincing as ever.
That's largely down to the work of Milk, the lead VFX studio on the series, but others are playing their part too. And that includes axisVFX, the Bristol and Glasgow-based visual effects studio established by Grant Hewlett and Howard Jones.
We profiled axisVFX's Glasgow studio in issue 185 of 3D World magazine, but it was the company's West Country arm that got to work on the latest episode, which is set in Bristol. And here's how they went about it...
Powers of interpretation
Recent episode of Doctor Who, Flatline, contains 66 VFX shots from axisVFX including a new multi-dimensional menace called The Boneless.
The axisVFX crew created the visual effects for the shots as well as conceiving, designing and developing the look and performance of this new 'impossible creature'. (You'll have to watch the episode to find out why they're impossible, though – we're going to keep this post as spoiler-free as possible!).
The VFX company were granted wide powers of interpretation in deciding how the creatures should look and behave, explains axisVFX's 3D visual effects supervisor Grant Hewlett.
"The script described how these creatures move, grow and evolve over time but everyone who read the words on the page imagined it differently in their head," he says. "So this was our biggest challenge, visualising something that had never been seen before, something that initially had to be flat but at the same time become sinister, threatening and frightening."
Following meetings with Doctor Who's executive producers Steven Moffat and Brian Minchin and director Douglas Mackinnon, axisVFX's design and concept team started producing concept artwork, in consulation with VFX art director Ste Dalton.
Taking influences from everything from Ferro fluids to Francis Bacon, they created more than 30 different pieces of digital concept art, explains axisVFX's 2D visual effects supervisor Howard Jones.
"We then quickly moved from 2D concepts into doing test sequences utilising 3D tools in Houdini and 2D tools in Nuke, Jones adds. "These tests and explorations were led by our FX lead Joe Thornley-Heard."
From XBox to mocap
After testing a number of solutions for the Boneless, including using Kinetic cameras from the Xbox to recreate 3D creatures live with real actors, the team settled on a more flexible way of working.
Grant Hewlett and axisVFX's creative director Stu Aitken worked together to deliver a plan that involved 3D-scanning all the actors in costume, followed by a motion capture shoot directed by Douglas Mackinnon. Hewlett worked closely on-set with Mackinnon, providing on the spot technical and creative solutions including shooting plates.
"Due to the complex nature of the script and the demanding shooting schedule," says Hewlett, "I really had to get hands-on: shooting plates that would later become shots, suggesting alternatives to save valuable shooting time and re-designing shots as we went."
Lighting and rendering
The lighting and rendering team led by CG supervisor Sergio Caires used all of the reference materials shot on set to light the creatures accurately. These rendered passes were then finessed by the compositing team and added to the 2D effects that were being applied to the shots.
For the 2D version of the Boneless, Mackinnon brought in some sea slugs as reference, as he felt they moved in an appropriately unnerving way. VFX supervisor Grant Hewlett and lead FX artist Joe Thornley Heard worked together on creating a CG version of the slug.
"These could then be combined and driven by various fluid dynamic processes making them move together as one mass," says Hewlett.
Creating the 2D Boneless effect was a challenge for the compositing team led by Carl Chittneden. "Taking the creatures Joe created in Houdini," says Howard Jones, "we settled on a treatment where they would start out invisibly hidden in the textures of the surrounding environment, then gradually reveal themselves as they move, dragging and displacing those surfaces with them.
"We accomplished this by using the rendered passes from Joe’s Houdini 3D setup to smear and distort the original plate in a variety of ways within Nuke. The result was a subtle yet 'impossible' treatment of the boneless that felt unnerving and other-worldly."
As well as the Boneless creatures themselves the axisVFX crew also created other effects, including the flattening of various CG props and live action actors by the Boneless, a shape-shifting Tardis and energy based force fields and blasts.