distance_to_closest_obstacle(pt, radius) cannot return properly while pt getting close to the ground about habitat-sim

[aclegg3]

Hey @Fanxing-LI

Interesting application. A few points of clarification about how the system works may help:

1. The navmesh (PathFinder) is an abstraction of the navigable area in a scene representing the agent as a cylinder and computing a mesh based on a voxelization of the scene geometry.
2. The distance_to_closest_obstacle function gives distance to the nearest mesh edge from the snapped point.
3. Pathfinder does not use the collision proxy for the asset, it only uses the NavMeshSettings which by default is computed from the agent's height and radius config.
4. The navmesh will not be a great representation if you want to the drone to be able to fly/hover over obstacles in addition to avoiding them.

It sounds like you have a clever way of using the navmesh for a drone to avoid walls and large obstacles, but you want vertical distance (e.g. to floor and maybe ceiling) in addition. One way to accomplish this is to setup some raycasts as sensors. For example, cast a ray from the center of your drone down the Y-axis and use the first hit distance (which isn't your drone). Similarly, you could setup rays in other directions for additional sensors.

Another option (if the world is mostly static, like scan scenes) would be to pre-compute a signed distance field in the space and then query from the cache for your drone's position.