Any way to get a bounding box from a three.js Object3D?

问题:

I'm loading an OBJ file using Three.js and OBJLoader.js. This returns a Three.Object3D object, which has what you'd expect from a 3D model (position vector, up vector...)

What I can't figure out is how to get a bounding box for it-- is this possible?

回答1:

You don't need to iterate over all children of the object; there's a method in the library to do this: THREE.Box3#setFromObject: see the docs. For example, you can do:

var bbox = new THREE.Box3().setFromObject(obj); 

to get the bounding box of obj, including all of its children, and accounting for any translations, rotations, etc.

Note that the BoundingBox helper is intended to draw a bounding box in the scene, not for just calculating the bounding box of some object.

回答2:

If you want the bounding box position and size as the object appears in the scene, try the BoundingBoxHelper:

var helper = new THREE.BoundingBoxHelper(someObject3D, 0xff0000); helper.update(); // If you want a visible bounding box scene.add(helper); // If you just want the numbers console.log(helper.box.min); console.log(helper.box.max); 

The .boundingBox on the geometry doesn't account for translations, rotations, or scaling that may be applied to the parent mesh and etc. and I found it very difficult to adjust for that manually, but the helper does it for you.

回答3:

For any shape, on its geometry object, there is a boundingBox property. This property holds a THREE.Box3 object. This Box3 object consists of two THREE.Vector3 objects, min and max.

var geometry = new THREE.CylinderGeometry(...); var material = new THREE.LineBasicMaterial(...); var mesh = new THREE.Mesh(geometry, material);  var boundingBox = mesh.geometry.boundingBox.clone(); alert('bounding box coordinates: ' +      '(' + boundingBox.min.x + ', ' + boundingBox.min.y + ', ' + boundingBox.min.z + '), ' +      '(' + boundingBox.max.x + ', ' + boundingBox.max.y + ', ' + boundingBox.max.z + ')' ); 

For more complex shapes, like those loaded from JSON Object files, the bounding box property is undefined by default. It must be computed explicitly.

var loader = new THREE.ObjectLoader(); loader.load(imagePath, function(object){      geometry = object.children[0].children[0].geometry;  // substitute the path to your geometry      geometry.computeBoundingBox();  // otherwise geometry.boundingBox will be undefined      var boundingBox = geometry.boundingBox.clone();     alert('bounding box coordinates: ' +          '(' + boundingBox.min.x + ', ' + boundingBox.min.y + ', ' + boundingBox.min.z + '), ' +          '(' + boundingBox.max.x + ', ' + boundingBox.max.y + ', ' + boundingBox.max.z + ')' ); } 

回答4:

Yes you would need something like this:

if (object instanceof THREE.Object3D) {     object.traverse (function (mesh)     {         if (mesh instanceof THREE.Mesh)         {             mesh.geometry.computeBoundingBox ();             var bBox = mesh.geometry.boundingBox;              // compute overall bbox             minX = Math.min (minX, bBox.min.x);             minY = Math.min (minY, bBox.min.y);             minZ = Math.min (minZ, bBox.min.z);             maxX = Math.max (maxX, bBox.max.x);             maxY = Math.max (maxY, bBox.max.y);             maxZ = Math.max (maxZ, bBox.max.z);         }     });      var bBox_min = new THREE.Vector3 (minX, minY, minZ);     var bBox_max = new THREE.Vector3 (maxX, maxY, maxZ);     var bBox_new = new THREE.Box3 (bBox_min, bBox_max);      scene.add (object); } 

EDIT:

This method is before the BoundingBoxHelper() or BoxHelper() were available

文章来源: Any way to get a bounding box from a three.js Object3D?