Geomerics - Advancing Technology Through Innovation

The Enlighten Manifesto

"Most likely the single most important aspect of cinematography is lighting.  Lighting contributes considerably to the emotional response an audience has watching a motion picture." (Wikipedia)

No-one would claim the visual quality of video games has yet reached that of film, but the challenges faced by the cinematographer and the game artist are the same: to achieve consistent, realistic lighting that creates the desired mood. The cinematographer is typically forced to experiment with extra lights and occluders off-camera in order to achieve presentable results.  With current technology, the game artist is obliged to do the same, in what can be a frustrating and time-consuming process that ultimately only decreases the possibilities for interactivity.

With Enlighten, realism comes for free.  Light from all sources in the scene is accurately computed in real-time; and not just the first bounce, but the whole global solution.  With a fully immersive environment guaranteed, the artist is free to concentrate on quality.  And since the lighting calculations are fully configurable, he can even change the laws of physics... what the cinematographer wouldn't give for the possibilities offered by Enlighten!

Why is Real-Time Radiosity Important?

Current game lighting technology requires large numbers of lights. Artists use additional lights to fill in areas that, in reality, are lit by light reflected off other surfaces in the scene. With dynamically computed radiosity one can achieve far greater realism with only a handful of light sources. Enlighten brings physically correct dynamic lighting to this generation of game development. Enlighten computes all bounced lighting and global illumination in real time – the first time this has ever been possible. By removing the need for artists to painstakingly mimic realistic lighting, time to create artwork is dramatically reduced. And with frame rates over 100fps Enlighten can be incorporated into any game setting.

What is Global Illumination?

Whenever light shines on a surface, a portion of it is reflected.  This seemingly obvious fact is typically ignored in most games lighting models because it massively increases the complexity of the computations.  Most objects reflect incident light in a broad range of directions.  This ‘diffuse’ emission means that when a surface it lit, in can in principle light every other surface it can see; each surface it lights can also then relight the world, leading to an infinitely long iterative sequence that converges on the true physical lighting solution observed in reality.

If we add into the mix the potential of some surfaces to reflect in a highly ‘specular’ manner such as a mirrored surface, or to focus light and cause caustics such as a glass of water, then we enter the realm of ‘global illumination’. In essence, this is computing a physically correct lighting model for the entire world. Typically the domain of the high-end renderers used in the CGI and film industries, such solutions can take hours (or even days) to compute and hence are totally unsuitable to the real time needs of games.

What is Radiosity?

Various compromises have to be made in real time video game graphics. We typically split the subject of global illumination into two pieces: the highly specular and the purely diffuse.  Highly specular global illumination typically requires ray tracing and can usually only be included in games using a series of tricks or pre-computes. It is the diffuse part that is of most interest in terms of setting the mood of a scene. Diffuse global illumination goes under the name of ‘radiosity’.

Radiosity fully models the subtle effects arising from the diffuse inter-reflections of light between surfaces, and it dominates many real-world situations.  Shadows in exterior scenes are filled in by light reflecting from bright areas, and the ‘mood’ of a room is heavily influenced by the colours of the walls, a red wall makes the room feel warm and welcoming, a blue wall makes it feel cold and menacing.

The Potential of Real-Time Radiosity

The ability to compute radiosity effects in real time breaks a whole array of restrictions under which games are currently made. Without real-time radiosity the diffuse lighting solution is often computed off-line and layered on top of the geometry as a ‘light-map’.  Then if a light is turned on, or the sun is obscured, nothing happens! A noticeable example of this is when one is exploring scenes set in a dark room with a torch.  In reality we know how exploring such a room will cause a dull glow due to bounced light, but in practice games cannot achieve this effect.

The same goes for how characters are immersed into a scene.  If you do not know the correct radiant light in the vicinity of a character they end up being lit in an inconsistent manner and do not appear to be correctly placed in their world.

Artistic freedom

The ability to move lights around and rapidly see the effects on the world frees up artists to be far more creative.  Instead of being restricted to a limited set of lights and, typically, a limited colour palette as well, artists will be able to apply bright neon area lights and immediately explore the consequences for the look of a world. The design possibilities are almost endless once one can rely on the fact that the radiosity light will be computed in real time in the game.

Game play potential

Games use many tricks to increase the realism of their lighting. One is to use uniform flat colour palettes so that the lack of colour bleeding from the world onto characters is not so keenly noticed. This has led to a plethora of uniformly grey / brown shooters on the shelves today. Another is to fast but approximate solutions for soft shadows, but these still tends to look out of place unless the correct lighting environment is known.

A simple game that illustrates the need for radiosity is a painting game. Imagine a world in which you are free to roam and paint the walls of any room any colour you like – or to project lights or movies onto walls. Now think how flat that world would look if no radiosity lighting was included!