三.js raycaster 交集 [英] Three.js raycaster intersection

问题描述

我编写了下面的代码来获得与 3d 形状的交点.它工作得很好，但如果有两个与形状的交点，它只会返回最远的交点，而我需要与形状最近的交点.我怎样才能找到最近的十字路口?

I wrote the code below to get intersection point with a 3d shape. It works well but if there are two intersection point with shape, it returns me only the farest intersection while I need the nearest intersection with the shape. How can I do to get the nearest intersection?

  /*here I create a cube*/

            var geometry0 = new THREE.Geometry()
            geometry0.vertices = [new THREE.Vector3(0.5, -0.5, 0.5), new THREE.Vector3(-0.5, -0.5, 0.5), new THREE.Vector3(-0.5, -0.5, -0.5), new THREE.Vector3(0.5, -0.5, -0.5), new THREE.Vector3(0.5, 0.5, 0.5), new THREE.Vector3(-0.5, 0.5, 0.5), new THREE.Vector3(-0.5, 0.5, -0.5), new THREE.Vector3(0.5, 0.5, -0.5)];
            geometry0.faces = [new THREE.Face3(3, 2, 1), new THREE.Face3(3, 1, 0), new THREE.Face3(4, 5, 6), new THREE.Face3(4, 6, 7), new THREE.Face3(0, 1, 5), new THREE.Face3(0, 5, 4), new THREE.Face3(1, 2, 6), new THREE.Face3(1, 6, 5), new THREE.Face3(2, 3, 7), new THREE.Face3(2, 7, 6), new THREE.Face3(3, 0, 4), new THREE.Face3(3, 4, 7)];
            geometry0.computeFaceNormals();
            geometry0.computeVertexNormals();
            var material0 = new THREE.MeshBasicMaterial({color: 0x39d2dbe7fff39d2, transparent: true, opacity: 0});
            mesh0 = new THREE.Mesh(geometry0, material0);
            egh0 = new THREE.EdgesHelper(mesh0, 0x000);
            egh0.material.linewidth = 2;
            scene.add(egh0);


            objects.push(mesh0);
            projector = new THREE.Projector();
            console.log(objects);
            mouse2D = new THREE.Vector3(0, 10000, 0.5);//controllare i valori



    /* here I create the ray */


document.addEventListener('click', onDocumentMouseClick, false);


        function onDocumentMouseClick(event) {

            event.preventDefault();

            mouse2D.x = (event.clientX / window.innerWidth) * 2 - 1;
            mouse2D.y = -(event.clientY / window.innerHeight) * 2 + 1;
             var vector = new THREE.Vector3( mouse2D.x, mouse2D.y, 0.5 );

            projector.unprojectVector( vector, camera );

            var raycaster = new THREE.Raycaster( camera.position, vector.sub( camera.position ).normalize() );


            var intersects = raycaster.intersectObjects( objects );

            if (intersects.length > 0) {
                console.log("ok");} 

如果我检查 intersects[0].point 我只能看到立方体的最远点面相交，而不是第一个(例如，如果你看着你面前的立方体并制作一条射线，这条射线在相交之前第一个面，然后与第一个面后面的第二个面相交.)此代码的目标是仅在您单击顶点时创建一个事件.所以在这之后我写了代码来计算从点击点和所有顶点的欧几里德距离并返回最接近点击点的顶点.如果您有其他想法仅在单击顶点时触发事件，欢迎使用.

If I check intersects[0].point I can only see the farest point face of cube intersected and not the first (for example,if you look at a cube in front of you and make a ray,this ray before intersect the first face and after intersect second face behind the first.) The goal of this code is to create an event only when you click on vertices. So after this I wrote code to calculate the euclidean distance from point of click and all vertices and return the vertice nearest to the point of click. If you have other idea to fire an event only when you click on vertices is welcome.

推荐答案

是的，光线投射的基本思想是我们投射一条垂直于平面的光线，我们找出了射线已经相交.

Yes, the basic idea of ray casting is that we project a ray perpendicular to the plane we find out the list of objects that the ray has intersected.

因此，访问第一个元素所需要做的就是添加以下代码.

So all you have to do to access the first element is adding the following piece of code.

var intersects = raycaster.intersectObjects(objects);

if (intersects.length > 0) {
       var firstIntersectedObject  = intersects[0];
       // this will give you the first intersected Object if there are multiple.
    }

这是我的另一篇SO帖子我已经以更详细的方式解释了一些事情，您可以参考它以更好地了解光线投射的功能.

Here is one of my other SO post in which I have explained things in a bit more detailed way, you can refer it to better understand how raycasting functions.

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