Now that we added HDR rendering support, you may have noticed that our average luminance value is very unstable when the content of the HDR image changes due to camera movement or changes in the scene. This instability results in noticeable changes to the tone mapping range which changes the brightness of the LDR image.
When we move from a bright to a dark area, our eyes need some time to gradually adapt to these changes. This recipe adds a similar adaptation to our average luminance calculation to smooth those kinds of transitions.
Adding adaptation will require an additional buffer to store the previous frame's luminance. This buffer should have the exact same descriptor values as the average luminance buffer we added in the preceding recipe. Similar to the average luminance buffer, the new buffer will also require a UAV and SRV. On each frame we render, we will store the average luminance into one of the buffers and read the previous frames average luminance from...