如何投射可见光线threejs

Question

我想用相机的视野瞄准物体（因为用户会看着物体，而不是用鼠标指向它）。

我正在像这样从相机投射光线

rotation.x = camera.rotation.x;
    rotation.y = camera.rotation.y;
    rotation.z = camera.rotation.z;
    raycaster.ray.direction.copy( direction ).applyEuler(rotation);
    raycaster.ray.origin.copy( camera.position );

var intersections = raycaster.intersectObjects( cubes.children );

这让我到达了十字路口，但有时它似乎会迷路。所以我想添加瞄准（十字准线）。那将是光线末端或中间的物体（网格）上的某种东西。

如何添加？当我创建一条常规线时，它位于相机前面，因此屏幕会变黑。

Answer 1

您可以将由简单几何构造的十字准线添加到您的相机，如下所示：

var material = new THREE.LineBasicMaterial({ color: 0xAAFFAA });

// crosshair size
var x = 0.01, y = 0.01;

var geometry = new THREE.Geometry();

// crosshair
geometry.vertices.push(new THREE.Vector3(0, y, 0));
geometry.vertices.push(new THREE.Vector3(0, -y, 0));
geometry.vertices.push(new THREE.Vector3(0, 0, 0));
geometry.vertices.push(new THREE.Vector3(x, 0, 0));    
geometry.vertices.push(new THREE.Vector3(-x, 0, 0));

var crosshair = new THREE.Line( geometry, material );

// 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;

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

三.js r107

http://jsfiddle.net/5ksydn6u/2/

---

如果您没有特殊的用例需要像您一样从相机中检索位置和旋转，我想您的“徘徊”可以通过使用这些参数调用您的 raycaster 来解决。：

raycaster.set( camera.getWorldPosition(), camera.getWorldDirection() );
var intersections = raycaster.intersectObjects( cubes.children );

---

投射可见光线 然后，您可以通过使用箭头助手绘制箭头，在 3D 空间中可视化您的光线投射。在您的光线投射之后执行此操作：

scene.remove ( arrow );
arrow = new THREE.ArrowHelper( camera.getWorldDirection(), camera.getWorldPosition(), 100, Math.random() * 0xffffff );
scene.add( arrow );