Hellgate: London Designer Diary

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Written by BuckGB on May 5th, 2005

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I spend a lot of time profiling the game both for video and CPU performance. My goal is to keep the balance of features, cost and workload between processors in a Happy Place(tm). Every feature has a cost, a minimum hardware spec, a fallback method and a visual or performance benefit. For example, consider full-screen distortion effects like heat shimmering. Their cost is almost purely in pixel shading and texture and framebuffer bandwidth (transferring pixels to and from video memory). That means on computers with really high-end video cards where the CPU is the limiting factor, they are essentially free. Conversely, on the machine with an average video card where pixel-pushing is the bottleneck, they can be incredibly costly. A fallback for those cases would be a cheaper effect (perhaps reducing the number of passes on the effect or using a simple texture lookup in place of more interesting and complex per-pixel math) or getting rid of it altogether. The min-spec would obviously be defined as the point where the technique is unusable. If that's too high and the benefit of the effect is too low (say, it's only used on a tiny stained glass window high up in a wall that you never get close to), it may be dropped in favor of an effect with more bang-for-the-buck.

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