Box3 now supports computing minimal bounds for setFromObject

Author: arikwex

src/math/Box3.d.ts

@@ -19,7 +19,7 @@ export class Box3 {
 	setFromBufferAttribute( bufferAttribute: BufferAttribute ): this;
 	setFromPoints( points: Vector3[] ): this;
 	setFromCenterAndSize( center: Vector3, size: Vector3 ): this;
-	setFromObject( object: Object3D ): this;
+	setFromObject( object: Object3D, minimal?: boolean ): this;
 	clone(): this;
 	copy( box: Box3 ): this;
 	makeEmpty(): this;
@@ -29,7 +29,7 @@ export class Box3 {
 	expandByPoint( point: Vector3 ): this;
 	expandByVector( vector: Vector3 ): this;
 	expandByScalar( scalar: number ): this;
-	expandByObject( object: Object3D ): this;
+	expandByObject( object: Object3D, minimal?: boolean ): this;
 	containsPoint( point: Vector3 ): boolean;
 	containsBox( box: Box3 ): boolean;
 	getParameter( point: Vector3, target: Vector3 ): Vector3;

src/math/Box3.js

@@ -144,11 +144,11 @@ Object.assign( Box3.prototype, {
 
 	},
 
-	setFromObject: function ( object ) {
+	setFromObject: function ( object, minimal = false ) {
 
 		this.makeEmpty();
 
-		return this.expandByObject( object );
+		return this.expandByObject( object, minimal );
 
 	},
 
@@ -237,7 +237,7 @@ Object.assign( Box3.prototype, {
 
 	},
 
-	expandByObject: function ( object ) {
+	expandByObject: function ( object, minimal = false ) {
 
 		// Computes the world-axis-aligned bounding box of an object (including its children),
 		// accounting for both the object's, and children's, world transforms
@@ -248,24 +248,39 @@ Object.assign( Box3.prototype, {
 
 		if ( geometry !== undefined ) {
 
-			if ( geometry.boundingBox === null ) {
+			if ( minimal && geometry.attributes != undefined && geometry.attributes.position !== undefined ) {
 
-				geometry.computeBoundingBox();
+				const position = geometry.attributes.position;
+				for ( let i = 0, l = position.count; i < l; i ++ ) {
 
-			}
+					_vector.set( position.getX( i ), position.getY( i ), position.getZ( i ) );
+					_vector.applyMatrix4( object.matrixWorld );
+					this.expandByPoint( _vector );
+
+				}
+
+			} else {
+
+				if ( geometry.boundingBox === null ) {
 
-			_box.copy( geometry.boundingBox );
-			_box.applyMatrix4( object.matrixWorld );
+					geometry.computeBoundingBox();
 
-			this.union( _box );
+				}
+
+				_box.copy( geometry.boundingBox );
+				_box.applyMatrix4( object.matrixWorld );
+
+				this.union( _box );
+
+			}
 
 		}
 
 		const children = object.children;
 
 		for ( let i = 0, l = children.length; i < l; i ++ ) {
 
-			this.expandByObject( children[ i ] );
+			this.expandByObject( children[ i ], minimal );
 
 		}
 

test/unit/src/math/Box3.tests.js

@@ -10,8 +10,11 @@ import { Mesh } from '../../../../src/objects/Mesh';
 import { BufferAttribute } from '../../../../src/core/BufferAttribute';
 import {
 	BoxGeometry,
-	BoxBufferGeometry
+	BoxBufferGeometry,
 } from '../../../../src/geometries/BoxGeometry';
+import {
+	SphereBufferGeometry,
+} from '../../../../src/geometries/SphereGeometry';
 import {
 	negInf3,
 	posInf3,
@@ -168,6 +171,30 @@ export default QUnit.module( 'Maths', () => {
 
 		} );
 
+		QUnit.test( "setFromObject/Minimal", ( assert ) => {
+
+			var a = new Box3( zero3.clone(), one3.clone() );
+			var object = new Mesh( new SphereBufferGeometry( 1, 32, 32 ) );
+			var child = new Mesh( new SphereBufferGeometry( 2, 32, 32 ) );
+			object.add( child );
+
+			object.rotation.setFromVector3(new Vector3(0, 0, Math.PI / 4.0));
+
+			a.setFromObject( object );
+			var rotatedBox = new Box3(
+				new Vector3( - 2 * Math.SQRT2, - 2 * Math.SQRT2, - 2 ),
+				new Vector3( 2 * Math.SQRT2, 2 * Math.SQRT2, 2 )
+			);
+			assert.ok( compareBox( a, rotatedBox ), "Passed!" );
+
+			a.setFromObject( object, true );
+			var rotatedMinBox = new Box3(
+				new Vector3( - 2, - 2, - 2 ),
+				new Vector3( 2, 2, 2 )
+			);
+			assert.ok( compareBox( a, rotatedMinBox ), "Passed!" );
+		} );
+
 		QUnit.test( "clone", ( assert ) => {