What is the Fade Height option in Marlin?

Question

Going through the printer options, I came across the Fade Height option under Bed Leveling section.

What is it and what is its use in Marlin firmware?

Answer 1

Fade Height is used to specify the height above the bed at which the printer should stop fading the bed leveling correction. Bed leveling is gradually decreasing with each successive layer until fade height is reached. From this height, bed leveling compensation becomes turned off.

For example, if the bed is slightly warped or uneven, the printer may need to compensate by lowering the nozzle at the center of the bed but less so near the edges of the bed. By setting Fade height, the printer will gradually decrease the correction as it moves away from the center of the bed, resulting in more accurate print.

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According to Marlin docs:

With Fade height enabled, bed leveling correction is gradually reduced as the nozzle gets closer to the Fade height. Above the Fade height no bed leveling compensation is applied at all, so movement is machine true.