A basic line with distance collider. It's called a pill collider because of the pill shape it.

PillCollision.js

import { Vector3, Object3D, BufferGeometry, Math as M, Group, LineBasicMaterial, Line, Line3, CylinderBufferGeometry, BufferAttribute, SphereBufferGeometry  } from "three";

export function Pill(start, end, radius) {
	Object3D.call(this);

	this.radius = radius;
	this.type = "Pill";
	this._start = start;
	this._end = end;
	var geometry = new BufferGeometry();
	var line = new BufferGeometry();
	this.line = line;
	this.geometry = geometry;

	var vertices = new Float32Array([
		start.x,
		start.y,
		start.z,
		end.x,
		end.y,
		end.z
	]);
	this.line.addAttribute("position", new BufferAttribute(vertices, 3));

	this.delta = function(target = new Vector3()) {
		return target.copy(this.end).sub(this.start);
    };

	Object.defineProperty(this, "start", {
		get: function() {
			var arr = line.attributes.position.array;
			return this.localToWorld(this._start.set(arr[0], arr[1], arr[2]));
		}
	});

	Object.defineProperty(this, "end", {
		get: function() {
			var arr = line.attributes.position.array;
			return this.localToWorld(this._end.set(arr[3], arr[4], arr[5]));
		}
	});
	
	
}

Pill.prototype = Object.assign(Object.create(Object3D.prototype), {
	constructor: Pill
});

export function PillHelper(pill) {
	Object3D.call(this);

	this.type = "PillHelper";
	this.pill = pill;
	var start = pill.start;
	var end = pill.end;
	var radius = pill.radius;
 
	var cylinder = new CylinderBufferGeometry( radius, radius, start.distanceTo(end), 8,1, false );
	var sphere = new SphereBufferGeometry( radius, 8, 4 );
	var sphere2 = new SphereBufferGeometry( radius, 8, 4 );
			sphere.translate(0,-start.distanceTo(end)*0.5,0);
			sphere2.translate(0,start.distanceTo(end)*0.5,0);
	this.material = new LineBasicMaterial({ color: Math.random() * 0xffffff });
	var l3 = new Line3(start, end);
	var center = l3.getCenter(new Vector3())
	this.group = new Group();
	this.group.add(new Line(sphere, this.material));
	this.group.add(new Line(sphere2, this.material));
	this.group.add(new Line(cylinder, this.material));
	this.group.position.copy(center);
	this.group.lookAt(start);
	this.group.rotateX(M.degToRad(90))
	this.add(this.group)
	this.update = function () {
		this.position.copy(this.pill.position);
		this.rotation.copy(this.pill.rotation);
		this.scale.copy(this.pill.scale)
	} 
	this.update();
}

PillHelper.prototype = Object.assign(Object.create(Object3D.prototype), {
	constructor: PillHelper
});

function clamp(n = 0, min = 0, max = 1) {
	if (n < min) return min;
	if (n > max) return max;
	return n;
}

export function testPill(pill1, pill2, c1 = new Vector3(), c2 = new Vector3()) {
	var dist = closestPoint(pill1, pill2, c1, c2);
	var radius = pill1.radius + pill2.radius;
	//console.log(dist, radius * radius);
	return dist <= radius * radius;
}

var d1a = new Vector3();
var d2a = new Vector3();

export function closestPoint(line1, line2, c1 = new Vector3(), c2 = new Vector3()) {
	var d1 = line1.delta(d1a);
	var d2 = line2.delta(d2a);
	var r = line1.start.clone().sub(line2.start);

	var a = d1.dot(d1);
	var e = d2.dot(d2);
	var f = d2.dot(r);

	var s = 0;
	var t = 0;

	if (a <= Number.EPSILON && e <= Number.EPSILON) {
		var s = 0;
		var t = 0;
		c1.copy(line1.start);
		c2.copy(line2.start);
		var dist = c1.clone().sub(c2);
		return dist.dot(dist);
	}

	if (a <= Number.EPSILON) {
		s = 0;
		t = f / e;
		t = clamp(t);
	} else {
		var c = d1.clone().dot(r);
		if (e <= Number.EPSILON) {
			t = 0;
			s = clamp(-c / a);
		} else {
			var b = d1.clone().dot(d2);
			var denom = a * e - b * b;
			if (denom != 0) {
				s = clamp((b * f - c * e) / denom);
			} else {
				s = 0;
			}

			t = (b * s + f) / e;

			if (t < 0) {
				t = 0;
				s = clamp(-c / a);
			} else if (t > 1) {
				t = 1;
				s = clamp((b - c) / a);
			}
		}
	}

	c1.copy(line1.start.clone().add(d1.multiplyScalar(s)));
	c2.copy(line2.start.clone().add(d2.multiplyScalar(t)));

	var dist = c1.clone().sub(c2);
	return dist.dot(dist);
}