Potree: fix vertical area measurements

app/static/app/js/vendor/potree/build/potree/potree.js

@@ -54099,14 +54099,16 @@
 		getArea () {
 			let area = 0;
 			let j = this.points.length - 1;
-
 			for (let i = 0; i < this.points.length; i++) {
+				let p0 = this.points[0].position;
 				let p1 = this.points[i].position;
 				let p2 = this.points[j].position;
-				area += (p2.x + p1.x) * (p1.y - p2.y);
+				let a = (p2.y - p0.y) * (p1.z - p0.z) - (p2.z - p0.z) * (p1.y - p0.y);
+				let b = (p2.x - p0.x) * (p1.z - p0.z) - (p2.z - p0.z) * (p1.x - p0.x);
+				let c = (p2.x - p0.x) * (p1.y - p0.y) - (p2.y - p0.y) * (p1.x - p0.x);
+				area += Math.sqrt(a * a + b * b + c * c);
 				j = i;
 			}
-
 			return Math.abs(area / 2);
 		};