Real-Time Rendering, Third Edition, 3rd Edition

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854 18. Graphics Hardware

the latency when requesting access to texel data. One technique for hiding

this type of latency is described on page 847.

A different type of latency is that from reading back data from GPU to

CPU. A good mental model is to think of the GPU and CPU as separate

computers working asynchronously, with communication between the two

taking some effort. Latency from changing the direction of the flow of

information can seriously hurt performance. When data is read back from

the accelerator, the pipeline often has to be flushed before the read. During

this time, the CPU is idle. An example of a read-back mechanism that does

not produce a stall is the occlusion query. See Section 14.6.1. For occlusion

testing, the mechanism is