Defect

I get to see a lot of scripts, breakdowns, and previs around the studio.  Every now and then I'll come across a shot that grabs me from the first moment I see it.  I'm a sucker for slow dramatic camera moves, heroic signature poses, or epic environments.  This is one of those special shots.

From the 2009 BAFTA award winning BBC mini-series The Day of the Triffids, this shot is also a great example of blending live action practical set pieces with visual effects enhancements to create a level a realism which would have been difficult to achieve with visual effects alone.  We were called upon to create the aftermath from a downed commercial airliner in the streets of London.  The plane tears a path through the city leaving a trail of destruction in it's wake.  We had to extend the two buildings on the right, one of which was destroyed in the crash, the crumbling and burning buildings, street and London skyline beyond.

Camera Projections in FusionOriginally our plan was to build a full CG model of the airplane which was to be featured in several shots, but after seeing the footage we decided that a simple multi-plane approach would be more flexible and cost effective.  I aligned several image planes based on the point cloud data I received from our matchmoving department.  I used three different camera projections for the set extension on the right, two for the buildings and one for the tree.  The airplane was made up of two more projections, one for the tail section and one for the fuselage.  And finally, the background building, street and city extension comprised of a multi-layered matte painting.  All of the camera Fusion Flowprojections were done using Fusion's 3D environment.  Once the geometry was aligned with the footage and all of the camera projections were set up, I could quickly swap out revisions from matte painter, Juan Garcia, without having to re-render layers in 3D.  This also allowed me to precomp many layers of fire and smoke elements onto still background images before re-projecting them onto the geometry.

I had great practical reference for the fire and interactive lighting from the footage.  Using filmed fire and smoke effects elements, I layered in pockets of fire and bounce light around the destroyed buildings.  I also added fire inside and around the downed aircraft and on the piles of debris lining the city streets, creating pools of light which revealed just enough detail to bring the environment to life.  I even used Fusion's procedural noise tool to create additional smoke layers for the composite.  Finally, layers of falling ash and paper helped to blend everything together.

There have been a number of articles describing how Spin VFX created the visual effects for the Screen Gems action thriller, Legion.  While they provide a really good overview, they don't cover any particular topic in detail.  I thought I'd give you a closer look at exactly how it was done, by breaking down an iconic shot from the film.  Along the way I'll talk about some of the challenges we faced while breathing life into Gabriel's computer generated wings.

Original Plate, Clean Plate, and Final CompositeThis is one of the shots that defined the look of the wings, and is one of my favorite shots from the diner fight sequence.  Gabriel (Kevin Durand) flies towards camera with a diving attack on Michael (Paul Bettany).  Inspired by the comic book superhero, this shot was often referred to as, 'the Thor shot.'  We started by rotoscoping the actor's upper-body, removing the wire rig, and replacing the missing ceiling tile which had been removed to accommodate the rig.  The matchmove department tracked the camera move, and object tracked the actor in order to 'attach' the wings to his back.  Based on 3D cyber scans of Kevin Durand, lead modeler Erin Nicholson built a low-resolution version of Gabriel in Maya to act as our digital stand-in.  Paying special attention to the upper-body, the layout department, led by Phil Dakin,  solved the camera and object tracks using PFTrack, and placed our Gabriel proxy model into the scene along with our tracked virtual camera.  Low-Resolution Proxy Model of GabrielAnimators carefully matched the actor's movements, which provided a solid foundation for the wing animation.  Animator Jongju Lee was assigned the task of providing the powerful yet graceful 'hero' wing animation.  Finally, rigging supervisor Glen Chang, ran a character effects pass to simulate the subtle effect of air rushing across the surface of the wings, causing the feathers to ruffle.  This added layer of detail really helped bring the wings to life.

HDRI Reference StillsOnce director Scott Stewart had approved the animation, the scene was passed to the lighting department.  Using HDRI reference photos of the set, lighting TD Paul George built a rig which accurately reproduced the physical lighting environment of the diner.  One of the challenging aspects of the wing design was striking a balance between natural looking feathers, and armoured ones capable of stopping bullets.  The small feathers along the top of the wings were softer and more organic, while the larger primary feathers at the wing-tips narrowed into hardened steel blades.  The wing textures were distressed, scratched and engraved with markings similar to those found on Gabriel's armour.  Ultimately, the task fell to the compositors to fine tune the final look and feel of the wings.  I used this shot to develop that look, and then built templates for the compositing team.  In order to give the artists maximum flexibility, we rendered multiple CGI passes as layered EXR files, Diffuse, Color, and Specular Lighting Passeswhich were later combined in Fusion to produce the final composite.  Among the layers were a number of utility channels including, a z-depth pass, various isolation mattes, and even a special iridescence pass, which created a subtle oily refraction effect on the wing surface.  Having this level of control presented it's own set of challenges.  For instance, how could we ensure that each artist produced a consistent look, allowing the shots to edit together seamlessly?

Fusion Template and Wing Macro Tool

By automating the process, we could ensure consistency among the compositors, and perhaps more importantly, we could build the individual shots much more efficiently.  I wrote a Fusion script, which both the lighters and compositors used to quickly build composites based on pre-defined templates.  They could simply select a sequence code, shot number, and lighting version, and the script would load the corresponding plate and CG wing layers into a basic comp.  The individual passes were piped into a custom wing macro tool, giving artists fine control over each of the components.  But, by limiting the artists to a fixed set of controls, we maintained continuity from shot to shot.  Since the roto and clean plates were completed ahead of time, once the lighting passes were rendered, we could quickly generate comps in a matter of seconds.  From there it was up to the compositing artists to integrate the wings seamlessly into the live-action plates.

Shadow Pass and Normal-MapThe digital Gabriel model was also used to cast shadows onto the wings, helping them to feel connected.  Atmospheric elements such as dust, and smoke were layered over the wings to provide interactivity with the environment.  Finally, a surface normal pass could be used to make last minute lighting adjustments in the comp, giving artists even more control.  Having this level of automation and control proved especially important during the final sequence of the film, where Michael returns to face Gabriel in the final battle.  This meant that the compositors had to integrate two sets of wings instead of only one.  Click below to watch the final shot, and be sure to check out my reel for more of my work on Legion.