Introduction of some graphics concepts, personal excerpts or sorting, as the entry quotes of personal articles;
ToneMapping：
Simply put, in order to make the image displayed on the monitor more realistic, the brightness greater than 1 is compressed in a certain way within the range of 0-1, so that we can observe it on the monitor;
Because people's perception of the world is close to logarithm, for example, the perception of brightness is roughly like this:
Specifically, it mainly calculates the current average brightness, and then selects a suitable brightness domain based on this average brightness; finally maps the entire scene to this brightness domain to get a correct calculation result; prevents the mapping of some pixels to the display The phenomenon of exposure;
With the development of shooting equipment, rendering methods, and display devices, HDR will gradually become standard; cameras and camcorders can capture the effects of HDR, and HDR pictures can be produced during the rendering process; these contents should be displayed on LDR equipment if necessary , You need the ToneMapping process to turn HDR into LDR; now high-end monitors and TVs can also directly display HDR content; however, unlike LDR, LDR is a certain range, and HDR is a very broad concept; Even if the two are HDR, their ranges may still be different; therefore, some people call this Variable Dynamic Range (VDR), variable dynamic range, because this H is not necessarily the other H; therefore, even in an HDR world , ToneMapping is still needed to change the dynamic range;
In fact, ToneMapping has been in existence since ancient times, and it is not a patent of computer graphics. In the early days, due to the limited contrast of the paint, Da Vinci and other masters would paint the content that needs to be expressed in very limited colors, even if the colors are not real; When the film was invented, the range of brightness that the film can express is limited, so the photographer will compress the highlight area and the shadow area in the direction of medium brightness, and develop the mapping relationship of the S curve; these are ToneMapping;
In the era of computer graphics development, there was only LDR at the earliest, and the color was 0-255; this situation has continued for a long, long time; in the late 1990s, the development of software and hardware made HDR a problem that can be considered; so The need for HDR to LDR has also emerged; after 2000, with the rapid advancement of GPU, game and movie special effects, ToneMapping has also undergone a series of evolutionary processes;