Evolution of an Airship

Posted Friday, October 26, 2012, 11:20 AM

When I decided to make my first short film, Eleanor Xandler: Temporal Detective, I knew immediately I would have to film the entire thing on greenscreen. I wanted to have real locations, but that was just so difficult and complicated to achieve as they had to be so specific in their look, and there was at least one part of the story that had to be on greenscreen anyway, that it made sense to just shoot everything in one place and fill in the backgrounds later.

There are flaws with this approach. When it's been done before in the past it has had a spotty success, and this is from professionals who really know what they're doing. Films like Sky Captain, the Star Wars prequels, Lord of the Rings, and King Kong, all have at least some greenscreen in every single shot, and a few environments that are entirely digital from top to bottom - and yet, to me, it's somehow glaringly obvious. Something about the compositing, the lighting, the staging, the artificiality, I'm not sure what, gives it away, at least to me. Even Avatar was convincing only a few times.

This gives me hope. My compositing skills are not ever going to be at professional level quality, but as, apparently, that can be a bit dodgy at the best of times I am in good company.

The first artificial background I have begun creating is for the opening sequence. I figure chronological order is as good a place to start as any. This means a cloud-filled sky, and a Steampunk Airship called The Wandering Star.

My first image is crude and simplistic. That's because I quickly slapped this model together in less than an hour, as a guide to show the cast and crew what we were filming. It oriented them somewhat, and gave them something to imagine was surrounding them as they stood in an endless sea of green.

After filming was complete I began to model the final version, carefully going through it step by step to include as much detail as I could. My normal approach to 3D modelling is to be a bit slapdash, to save time, cutting corners where things won't be seen, trying to find short-cuts to achieve the look I'm after. But this time I couldn't afford to be so cheap with my attention, and tried to give the model all the detail it needed, even if it meant hours of just pushing points around in a mundanely dull fashion.

The above image is a good start, but notice on the image below that there is an adjustment between the two. The windows are bigger, the railing is thicker and closer spaced. That's because I realised the scale was wrong.

I imagined the Wandering Star as a two-person vessel, that being Eleanor and her robot pilot Gadzooks. Therefore space to move could be minimal. She's not going to be playing Shuffleboard on the Lido Deck, after all, but she might have a passenger. I adjusted the scaling to a more logical size, from 25m down to 16m long. This is not only more realistic a scale, it also means she doesn't get too tiny in the shot when the framing shows the full profile of the airship.

I then added in the water tanks. Being steampunk, there needs to be steam. That means a lot of coppery brassy tanks and pipes and whatnot, so I put in the engines that drive the propellers. I also bought a plugin for Lightwave, a handy automatic rope generator that allows me to concentrate on the placement of the rope in a simple string, and it automatically fills in the twisty detail. The ropes do make the model polygon-heavy, which causes a bit of a slowdown, but it's well worth it. They add a level of realism that brings it to life, especially when twisted around the block-and-tackle.

Texturing is a complicated procedure, something I've never been very good at. You have to adjust so many factors to get things looking right that it gets bogged down in maths and angles and trickery that I frankly struggle under the weight of. Colour, diffusion, specularity, reflectivity, occlusion, transparency...

The brass and deck textures are relatively straight forward. Brass wraps around everything evenly, so it just has to be a golden metallic colour applied on all things I have deemed should be brassy. The deck is flat, and can have the texture projected directly from above. But the rest of the objects all have UV maps.

UV maps are when you unwrap an object, especially one with an unusual shape, so that it lays flat within a square page. That way you can apply the texture as a 2D image and it will apply itself to each individual polygon consistently. If you then subsequently move, rotate, or scale the object the texture remains fixed where you want it. But unwrapping each object into its UV shape is fiddly work. The weird shape of the airship's hull means I have to wrap a wooden plank texture that follows the curvature logically, with no distortion or irregularity. Laboriously adjusting the UV point by point is the only way to achieve that.

As I continued to apply the textures one by one I adjusted the model to fit. I'd suddenly have an idea of what should be wood, what brass, to give it that industrial elegance that steampunk requires. The rudder, for example, I was looking at in its plain wooden state and just thought it looked boring. So I added a brass strip and some bolts. Then another. Then some hinged joints. And some cog gearwheels. Suddenly it looked like it actually operated in a mechanical way, something quite elaborate yet logical. I am now tempted to adjust some of the other parts of the ship to match...

This is the final model of the ship, from the angle it will be seen most often, and in profile as it will rarely be seen at all.

Someone pointed out to me that the placement of the balloon causes an apparent imbalance that would make the rear of the ship topple backwards. But hey, it's science fiction. Technically the balloon isn't big enough to lift the vessel at all. I moved the balloon that far forward to give a sense of speed and dynamism to the design of the ship, though most of the time you won't see the ship from that side and it won't look quite so awkward in motion. But if it makes you feel any better, imagine there's a heavy counterweight in the forward hold.