Use physijs to give three.js Questions about adding physical effects？

Question

I created a ground, then I dug a gap in it, and finally added physical effects through physijs.

let Mesh = new THREE.Mesh(new THREE.BoxGeometry(800, 10, 800), material);
Mesh = new ThreeBSP(Mesh);

let Gap = new THREE.Mesh(new THREE.BoxGeometry(230, 10, 170), material);
Gap = new ThreeBSP(Gap);

Mesh = Mesh.subtract(Gap).toMesh(material);
Mesh = new Physijs.BoxMesh(Mesh.geometry, Mesh.material, 0);
scene.add(Mesh);

Then you create a collection with physical effects. The plan is to fall from the hole in the ground, and the result appears to be suspended in the hole. Why?

let geometry = new Physijs.BoxMesh(new THREE.CylinderGeometry(10, 15, 50, 25), material, 1);
geometry.position.set(0, 500, 0);
scene.add(geometry);

I'm building a house. I'm digging holes in the floor and walls to represent staircases and doors, and then I add physical effects to the floor and walls. In the plan, objects representing people can pass through these holes, but they are blocked. People are directly suspended above the holes in the stairway, and the door can't pass through, as if blocked by an invisible wall

Answer 1

Physijs.BoxMesh will just create a box with eight corners and flat planes in between. Have you looked into using Physijs.ConcaveMesh? I couldn't find any documentation, but you can see it in the source code.

Mesh = Mesh.subtract(Gap).toMesh(material);
Mesh = new Physijs.ConcaveMesh(Mesh.geometry, Mesh.material, 0);
scene.add(Mesh);