area of planeA is 4 (2 * 2)

area of planeB is 4 (2 * 2)

area of overlapped area is 1

after planeA merged planeB, the area of planeA should be 7 (4 + 4 - 1)

- the result is 8 == 4 + 4

```
var geom = planeA.geometry;
var area = 0;
for (var i = 0; i < geom.faces.length; i++) {
var face = geom.faces[i];
var tri = new THREE.Triangle(geom.vertices[face.a], geom.vertices[face.b], geom.vertices[face.c]);
var area = area + tri.getArea();
}
console.log(area);
```

- the result is -8,

```
planeA.geometry.mergeVertices();
var area = THREE.ShapeUtils.area(planeA.geometry.vertices);
console.log(area);
```

Is there a utility method to calculate the area of a complex plane with three.js?

Thanks in advance.