Here's a minimap for your spelunking delight! It should prevent you from getting lost in the caves. Do mind your step while looking at the map though!☠🦠
It's generated realtime at a radius around the player so it'll stay updated if the terrain is destroyed. The data comes from Godot Tilemaps and I query them somewhat similar to a raycast using an algorithm meant to plot pixel lines (Bresenham's line drawing algo). So for each ray I query the line's points' coordinates (that match to the tilemap) and step through them starting from the player until I hit a wall or the maximum range of the ray.
Each physics sim frame there are 16 rays (evenly divided around a circle) but I jitter the overall orientation randomly so that any leftover gaps are filled.