In VFX we often spend a good amount of time tied up with the technical aspects of computer animation that sometimes artistic control can often be a secondary thought. VFX lighting used to be a vastly complex subject which was limited greatly by technical challenges. Lighting for film is a purely artistic decision, with almost no thought put into the technical aspects of light. Light acts the way light always has. A single light source will bounce around a room, illuminating everything it touches. A 100 watt bulb will emit roughly 3x10^20 photos per second, that is more photons per second than there are grains of sand on earth. Each one of those photons hit a surface and some of the energy is lost in the collision, but the photon bounces off until it hits another surface. This cycle continues until the photon has lost all of its energy. In computer animation we have to calculate this as accurately as possible. While computer have progressed tremendously over the last 25 years, this level of calculation is just not possible and is unlikely to be possible in the next few decades.

So how do we create create animation at all? We cheat! We use simplistic lighting models to approximate what happens with real light. While real light sources produce a gigantic number of photons, we can get good results with a relatively low number of light rays particularly if we only care about photons that reach the camera. Up until the last 5-6 years, the vfx industry generally only calculated the first bounce of light, and the secondary bounces were faked using various techniques. This approach is referred to as REYES (Render Everything You've Ever Seen), and was pioneered from Pixar, who created the Renderman Specification. This technical limitation meant that lighting was a complex subject which required a lot of planning and forethought. Lighting couldn't be as fluid as it can be in the real world, and moving lights around once a scene was lit required significant work.

Recently a new breed of Renderers have taken over the Industry. These are referred to as Raytrace Renderers. Raytrace renderers have existed and been used for many years, but they often used biased techniques to calculate light, or were too slow to use in large scale work. However with the advent of better lighting algorithms and increased computing power accurate Raytrace rendering is an option. One of the pioneers in this regard is a renderer called Arnold. This has been our renderer of choice for the last 3/4 years. Raytrace rendering removes the technical limitation, by calculating light as accurately as possible including multiple bounces very quickly.

This means the technical challenge behind lighting is gone, and we are free to move light around as we would in real life. Now we are left with merely the artistic challenge behind lighting.

Thoughts by,
Rich