SIGGRAPH 2006 - Boston, MA - Sunday July 30 2006

HIGH DYNAMIC RANGE (“HDR”) TECHNOLOGY

HDR technology is the ability to display a wider range of light and dark colours on a screen. Both Valve and EA have produced videogames using HDR. Here is the scoop on what they had to say about HDR and their experiences using it.

Gary McTaggart – Valve Corporation

Gary believes it is important to use HDR because it can take people to very light and dark places in the game world. It can accurately create the bloom effects the human eye experiences when emerging from the dark into the light. It is also important for creating mood and realism in games. Finally, it can open up some really cool gameplay opportunities where you can hide in the dark where enemies can’t see you, or where they become blinded by dramatic increases in lighting.

In some ways, because it requires the use of fewer light sources, HDR cuts down on the amount of work lighters typically need to undertake. For example, using radiosity lighting from the sun causes light to bounce off surfaces around the game world. As such, lighters no longer have to place individual light sources in all parts of the world.

HDR was originally planned for use in Half-Life 2®, but time constraints meant that it had to wait for the expansion, The Lost Coast. Gary commented that it took Valve a while to figure out exactly how to implement HDR. This is because they had to find a way for it to support MSAA, and alpha blending, while also being generous with memory and performance.

Here’s the method they eventually settled on:

One thing Gary warned people to be careful of is managing the bloom amount and exposure range. This will ensure that playing the game remains an enjoyable experience.

Habib Zargarpour – EA Black Box

Habib was the Senior Art Director on Need for Speed: Most Wanted (“NFSMW”), a game that used HDR extensively.

The choice to implement HDR was made after many of the reference photographs (used to determine intended art style for the game) showed dramatic variations in the brightness of the lighting:

In addition to choosing to use HDR, the decision was also made to include dynamic time of day lighting in the game world, including full shadows for realism.

Many different exposure lengths were experimented with to get the sky looking right. A visual filter was then applied to give the game a yellow tint.

The results were impressive:

The various pitfalls Habib described can be summarized as follows:

• Unlike The Lost Coast, NFSMW was a console game. Attempting new lighting techniques on incremental versions of the new hardware was unpredictable.

• Don’t forget to limit the movement of the iris or you will receive unpredictable results.

• Setting the world too bright can cause the iris to overly darken some textures.

• Dynamic time of day lighting required every object in the game to be normal mapped.

• Trees made from flat cards looked much worse when lit with time of day lighting.

Conclusion

How will HDR change the way we experience videogames?

At first it’s just eye candy. Lighting bloom is this year’s solar flare. Everyone will have it because everyone else will have it, and it seems fairly easy to create.

Combined with real-time refraction and reflection, HDR makes water look absolutely incredible.

It seems to be the bright, rather than the dark end of the scale, that is more important because it often shows a greater level of detail in the game world. Any wet surfaces look incredibly life-like, and even dry surfaces show amazing detail when saturated by bright light. Examples seen were the head of an Ant Guard in The Lost Coast or the metallic paint surface of the BMW in NFSMW.

Although it’s just eye candy, HDR does arguably affect the mood of both The Lost Coast and NFSMW. Only time will tell just how important a role this technology will play in the evolution of videogames.

Hamish Millar

Web Editor

Vancouver ACM SIGGRAPH