void add( Object3D object ) {
 if ( object == this ) {
   print( 'THREE.Object3D.add: An object can\'t be added as a child of itself.' );
   return;
 }


 if ( object.parent != null ) {
   object.parent.remove( object );
 }

 object.parent = this;
 children.add( object );

 // add to scene
 Object3D scene = this;

 while ( scene.parent != null ) {
   scene = scene.parent;
 }

 if ( scene is Scene ) {
   scene.addObject( object );
 }

}

void applyMatrix ( Matrix4 matrix ) {
 this.matrix = matrix * this.matrix;

 this.scale = getScaleFromMatrix( this.matrix );

 Matrix4 mat = extractRotation(new Matrix4.identity(), this.matrix );
 this.rotation = calcEulerFromRotationMatrix( mat, this.eulerOrder );

 this.position = this.matrix.getTranslation();
}

clone() {

 // TODO

}

Object3D getChildByName( String name, bool doRecurse ) {
 int c;
 int cl = children.length;
 Object3D child, recurseResult;

 children.forEach((child){

   if ( child.name == name ) {
     return child;
   }

   if ( doRecurse ) {
     recurseResult = child.getChildByName( name, doRecurse );

     if ( recurseResult != null ) {
       return recurseResult;
     }
   }
 });

 return null;
}

localToWorld(Vector3 vector) => vector.applyProjection(matrixWorld);

void lookAt(Vector3 vector ) {
 // TODO: Add hierarchy support.

 makeLookAt(matrix, position, vector, up);

 if ( rotationAutoUpdate ) {
   rotation = calcEulerFromRotationMatrix( matrix, eulerOrder );
 }
}

void remove( Object3D object ) {

 int index = children.indexOf( object );

 if ( index != - 1 ){

   object.parent = null;
   children.removeAt(index);

   // remove from scene
   Object3D scene = this;

   while ( scene.parent != null ) {
     scene = scene.parent;
   }

   if (scene is Scene ) {
     scene.removeObject( object );
   }
 }
}

void translate( num distance, Vector3 axis ) {
 matrix.rotate3( axis );
 axis.normalize();
 position.add( axis.scale( distance ) );
}

void translateX( num distance ) => translate( distance, _vector.setValues( 1.0, 0.0, 0.0 ) );

void translateY( num distance ) => translate( distance, _vector.setValues( 0.0, 1.0, 0.0 ) );

void translateZ( num distance ) => translate( distance, _vector.setValues( 0.0, 0.0, 1.0 ) );

void updateMatrix() {

 if ( useQuaternion ) {
   setRotationFromQuaternion( matrix, quaternion );
 } else {
   setRotationFromEuler( matrix, rotation, eulerOrder );
 }

 matrix.setTranslation( position );

 if ( scale.x != 1.0 || scale.y != 1.0 || scale.z != 1.0 ) {
   matrix.scale( scale );
   boundRadiusScale = Math.max( scale.x, Math.max( scale.y, scale.z ) );
 }

 matrixWorldNeedsUpdate = true;
}

void updateMatrixWorld( {bool force: false} ) {

if (matrixAutoUpdate) updateMatrix();

 // update matrixWorld
 if ( matrixWorldNeedsUpdate || force ) {
   if ( parent != null ) {
     matrixWorld = parent.matrixWorld * matrix;
   } else {
     matrixWorld = matrix.clone();
   }

   matrixWorldNeedsUpdate = false;

   force = true;
 }

 // update children
 children.forEach((c) => c.updateMatrixWorld( force: force ) );

}

worldToLocal(Vector3 vector) {
 Matrix4 m = this.matrixWorld.clone();
 m.invert();
 m.transform3( vector );
}