Underestimation of distance to closest obstacles when there are unobserved grids in an ESDF map

[jwkodes]

The value of esdf at a certain grid indicates the euclidean distance to the nearest observed obstacle. If say there is an object that is entirely textureless and becomes unobserved in depth maps, the grids that are in this obstacle will not be allocated, and the grids outside and around this obstacle will tend to underestimate the true distance to an actual obstacle.

Is there a easy way to deal with this issue? For example, on top of having the euclidean signed distance to the nearest observed obstacle, is there also a way to obtain the distance to the nearest unobserved grid?