将对象附加到相机three.js

Question

我想将物体贴在相机或相机目标上。

我尝试使用crosshair.parent = camera;，但这不起作用：

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//Crosshair
var crosshair = new THREE.Mesh( new THREE.PlaneGeometry( 5, 5 ), mat_crosshair );
			// place it in the center
var crosshairPercentX = 50;
var crosshairPercentY = 50;
var crosshairPositionX = (crosshairPercentX / 100) * 2 - 1;
var crosshairPositionY = (crosshairPercentY / 100) * 2 - 1;

crosshair.position.x = crosshairPositionX * camera.aspect;
crosshair.position.y = crosshairPositionY;

crosshair.position.z = -0.3;
crosshair.rotation.y = 1.6;

camera.add( crosshair );
scene.add ( crosshair )

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有什么建议吗？