© Mark Platten 2006



  radial piston engine

- Lightwave
- 3ds Max
- mental ray
- After Effects

This sequence - a personal project - still rates as on of my all-time favourite pieces of work.

As a technical exercise, it pushed my 3D abilities further in various directions than I had previously taken them. It also addressed a latent desire - unsatisfied by my day job at the time - to actually design objects and the systems in which those objects operated and interacted, with as much respect to time-honoured engineering principles in the real world - as I could achieve. In sheer production terms, it also taught me volumes about the need for economy and optimal interplay between 3D and post.

The genesis of the sequence lies in a long-felt feeling that the radial piston engine has a certain compelling aesthetic, not to mention its significant place in aviation history.

My hands-on experiences maintaining, dismantling and rebuilding motorcycle engines in my occasionally well-spent youth had taught me to appreciate the design of internal combustion engines. In a sense, this project was a form of homage to an earlier, pioneer spirits of the petroleum age.

Not long after I'd started working at
Ace Effects, I was delighted to discover that the company kept a couple of radial aeroplane engines fitted with propellors - caged in the interests of safety - in stock. These formidable machines were mounted on moveable trolleys for easy hire-out on set: serious quantities of wind on demand.

The fundamental mechanics of the engine provided the greatest challenges.

As each piston fires, it drives a conrod down upon an eccentrically rotating crankwheel, which links to a central driveshaft with diametrically opposed flyweight which counters out the opposing forces.

As the crankwheel is pushed orbitally around its arbitrary center by each piston, it transfers its momentum to the central shaft: simple yet succinct in its implementation.

The radial piston engine was around for decades before the advent of the jet engine. In the course of my researches, I was intrigued by the recent efforts of a Canadian engineering firm, CKE, to produce a commercial, 5-cylinder version of this engine.

The project began life proper as a simple mesh modelling exercise in Lightwave. This was just skin, with no internals.

When I decided to revisit and animate the model, I started by dragging the original meshes into 3DS MAX and using them as templates to build the engine's interior mechanism.

Having gone so far down that road, I was disappointed to find that Max couldn't handle the motion of the hierarchical linkages. I tried bones, I tried everything I could.

These stills don't do justice to the motion paths involved, nor do they elucidate the problems I encountered. Suffice to say, I ended up building each piston and conrod assembly as a separate animation, which was referenced in the master scene.
So, the mechanism doesn't actually link as a genuine hierarchy. The IK defeated me - maybe it defeated MAX's capabilities too. I'm in no doubt that it could be scripted, but this was strictly a bedroom project by a then - non-MAX scripter.

With hindsight, I now realise I could have used the wonderful parameter rewiring dialog which appeared with MAX 5.

'mental ray' was my renderer of choice, and it repaid my efforts with some efficient reflective surfaces. The rendering was intensive, but not unusually so, and my trusty twin Athlons took it all in their stride.

Combustion events within each chamber were orchestrated on a 'per-cylinder' basis, using Digimation's 'Phoenix'. The timings took a thick wad of blank paper and half a kilo of pencil lead to resolve.
With the 3d work complete, the compositing stage came as a welcome change from the tedium of watching a single workstation bear the brunt of all the rendering. Now I could start exploiting all the material I had created, and concentrate on refining its appearance.

I'd ended up with a number of different 3d passes of the sequence - from mechanical assemblies to outer housing - and I threw them all into After Effects to fight it out.

Showing each cylinder firing was an imperative. A separate Max scene, derived form the original master, contained a keyed system of Phoenix events.

Tracking objects placed at the centre of each combustion chamber provided co-ordinates in AE for lens flares; to emphasise each point of ignition.
From early on in the planning stage, I knew that the final sequence would include various cross-fades between the internal mechanism and the exterior of the engine, and my rendering strategy acommodated this. In this still - slightly later than the one above - a separate render of the externals has been faded back in, over a composite of the interior action.

What might I add in retrospect? A full accurate hierarchy, for one thing. Motion blur courtesy of Mental Ray, maybe some more daring camera Xforms with DOF too. And HDRI on the reflections and lighting, although my botched cubic mapping here didn't perform too badly.

These days, I do try and get out more...