爲什麼ArrowHelper沒有達到目標？

Question

爲什麼下面ArrowHelper的尖端不直接撞擊目標球體？它只是錯過了一點。以下方向計算不夠精確？

var geometry = new THREE.SphereGeometry(1, 16, 16); 
var material = new THREE.MeshNormalMaterial(); 
var mesh = new THREE.Mesh(geometry, material); 
mesh.type = "node"; 
mesh.position.set(30, -87, -11); 
scene.add(mesh); 

geometry = new THREE.SphereGeometry(1, 16, 16); 
material = new THREE.MeshNormalMaterial(); 
mesh = new THREE.Mesh(geometry, material); 
mesh.type = "node"; 
mesh.position.set(28, 44, -14); 
scene.add(mesh); 

var sourcePos = new THREE.Vector3(30, -87, -11); 
var targetPos = new THREE.Vector3(28, 44, -14); 
var direction = new THREE.Vector3().subVectors(targetPos, sourcePos); 
var arrow = new THREE.ArrowHelper(direction.clone().normalize(), sourcePos, direction.length(), 0xff0000); 
scene.add(arrow); 

這是該question直接跟進的問題（我把它打開，因爲有可能更好的算法，而ArrowHelper，但似乎不準確也由這裏所描述的ArrowHelper問題引起的）。

Answer 1

這是three.js r.58中處理箭頭指向大致「直線向上」或「直下」的情況下的精確問題。

我想你會發現它在其他情況下工作正常。

three.js r.58