Tone mapping is not an exact science. Often, it is the process of experimenting with the parameters until you find something that works well and looks good.

We could improve the efficiency of the previous technique by implementing step 2 on the GPU using compute shaders (refer to Chapter 11, Using Compute Shaders) or some other clever technique. For example, we could write the logarithms to a texture, then iteratively downsample the full frame to a 1 x 1 texture. The final result would be available in that single pixel. However, with the flexibility of the compute shader, we could optimize this process even more.