How Valve are bringing horror movie visuals to Left 4 Dead

Color grading
In the movie industry, exposed film can be run through a colour grading process to apply tints and colour changes to the picture. L4D will employ similar effects. The game reduces the strength of colours in an environment while keeping teammates saturated and noticeable. “We use that to enhance gameplay,” explains Mitchell, “it’s not merely a stylistic thing.”

Film grain
Just as you’d see on a projected film, grain is a low-level visual noise, a sort of subtle static effect that will be laid over L4D’s action. Grain won’t be an overbearing effect, but it will be extra strong in darker parts of the screen, to imply more detail to the eye. Grainy dark alleyways also add a level of horror movie tension, and lend a feeling of thickness to the shadows.

Contrast enhancement
This effect sneaks into action in the more well-lit areas of the game. Contrast enhancement is something you’ll have come across if you’ve dragged photos from your digital camera into Photoshop – adjusting the contrast helps to more clearly define the light and dark areas of an image. L4D’s contrast enhancement won’t be too different, except it’ll be carried out on a frame-by-frame basis.

Vignetting
In vignetting the corners of the screen are darkened slightly. This happens with certain film lenses, but it often creates a pleasing effect. In L4D it’s used to frame the screen, and again, it’s subtle and effective. Combined with the other effects, it creates a unique look and feel to the game. What’s more, it’s not computationally expensive – you won’t take a performance hit.

Above: A shot before Valve’s expanded resources came along to give L4D a visual kick

Above: The sharper contrast and more prominent shadows provide a more eerie look

Aug 18, 2008