是三个BSP不能对使用THREE.ExtrudeGeometry的元素进行操作吗？

Question

我创建了一辆汽车使用THREE.ExtrudeGeometry，以下是我的代码：

function setExtMaterial(drawFunc,options,meshMaterial){
    var geom = new THREE.ExtrudeGeometry(drawFunc(),options);
    var shape = THREE.SceneUtils.createMultiMaterialObject(geom, [meshMaterial]);
    return shape;
}
function drawShap1(){
        var shape = new THREE.Shape();
        shape.moveTo(10,10);
        shape.splineThru([
            new THREE.Vector2(10.2,11.8),
            new THREE.Vector2(12,12)
        ])
        shape.lineTo(18,12);
        shape.splineThru([
            new THREE.Vector2(19.8,11.8),
            new THREE.Vector2(20,10)
        ])
        shape.lineTo(20,4);
        shape.lineTo(10,4);
        shape.lineTo(10,10);
        return shape;
    }
    var options1 = {
        amount:25,
        bevelThickness:1,
        bevelSize:1,
        beveSegments:60,
        steps:60,
        curveSegments:60
    }
    var mesh2 = new THREE.MeshPhongMaterial({
        color:new THREE.Color('#FAF808')
    });
    var carBody = setExtMaterial(drawShap1,options1,mesh2);
    carBody.position.set(-10,-3,15);
    carBody.rotation.y = Math.PI/2;
    car.add(carBody);
    console.log(carBody)

现在我使用console.log('carBody')查看打印内容，结果是：

  

群组{uuid：＆＃34; 896051F5-8F4E-43C8-8EFE-B9FC4A07B7DE＆＃34;，名称：＆＃34;＆＃34;，输入：   ＆＃34; Group＆＃34;，parent：Object3D，children：Array 1 ...}

carBody是Group？！

现在我使用subtract（）：

function subtract(obj1,obj2,mesh,target){
        var o1BSP = new ThreeBSP(obj1);
        var o2BSP = new ThreeBSP(obj2);
        var r = o1BSP.subtract(o2BSP);
        var result = r.toMesh(mesh);
        result.geometry.computeFaceNormals();
        result.geometry.computeVertexNormals();
        target.add(result);
    }
var windowFront = new THREE.Mesh(new THREE.CubeGeometry(1,5,9),mesh1);
windowFront.position.set(16,6,0);
subtract(carBody,windowFront,mesh2,car);

当我使用threeBSP＆quot; subtract（）时，Chrome指出了这个信息：

我看看ThreeBSP.js的代码，似乎只有Geometry和Mesh可以使用subtract（）来创建这样的门：

如何在我们使用THREE.ExtrudeGeometry创建的元素上使用subtract（）。非常感谢任何帮助。