Volume of Mesh Calculation With WebGL

//Created by Ken on Oct 20,2016 for volume compute when upload
function SignedVolumeOfTriangle(p1, p2, p3) {
var v321 = p3.X*p2.Y*p1.Z;
var v231 = p2.X*p3.Y*p1.Z;
var v312 = p3.X*p1.Y*p2.Z;
var v132 = p1.X*p3.Y*p2.Z;
var v213 = p2.X*p1.Y*p3.Z;
var v123 = p1.X*p2.Y*p3.Z;
var singnedVolume=(1/6)*(-v321 + v231 + v312 - v132 - v213 + v123);
return singnedVolume;
}

function VolumeOfMesh(points) {

var i= 0,vols=0;
var P1,P2,P3;
do
{
P1={X:points[i],Y:points[i+1],Z:points[i+2]};
P2={X:points[i+3],Y:points[i+4],Z:points[i+5]};
P3={X:points[i+6],Y:points[i+7],Z:points[i+8]};

vols+=SignedVolumeOfTriangle(P1, P2, P3);
i+=9;
}
while (i<points.length);

return customRound(Math.abs(vols)/1000,2);
}
function customRound(number,fractiondigits){
with(Math){
return round(number*pow(10,fractiondigits))/pow(10,fractiondigits);
}
}