angleCalc.js

function getMatrix4FromStreamedMatrix(streamedMatrix){
  var finalMatrix = new THREE.Matrix4()
  var divisor = 1
  var Rot1X = streamedMatrix[0]; 
  var Rot1Y = streamedMatrix[1] ;
  var Rot1Z = streamedMatrix[2] ;
  var Rot2X = streamedMatrix[3] ;
  var Rot2Y = streamedMatrix[4] ;
  var Rot2Z = streamedMatrix[5] ;
  var Rot3X = streamedMatrix[6] ;
  var Rot3Y = streamedMatrix[7] ;
  var Rot3Z = streamedMatrix[8] ;
  
// See answer here http://stackoverflow.com/questions/4833380/how-to-convert-a-3x3-rotation-matrix-into-4x4-matrix
  finalMatrix.set(  Rot1X, Rot1Y, Rot1Z, 0,
                    Rot2X, Rot2Y, Rot2Z, 0,
                    Rot3X, Rot3Y, Rot3Z, 0,
                    0, 0, 0, 1 )
  console.log('FINAL MATRIX ' + JSON.stringify(finalMatrix))
  return finalMatrix
}
var lowerLegRotMatrix = getMatrix4FromStreamedMatrix([-0.0726933181285858,0.95655220746994,0.282353401184082,0.0472477078437805,-0.279481798410416,0.958987742662429,0.996234536170959,0.0830524861812592,-0.0248785316944122])
var upperLegRotMatrix = getMatrix4FromStreamedMatrix([0.13940124027431,-0.10846203379333,-0.98427812103182,-0.0556552428752184,0.991554081439971,-0.117146134376526,0.988670787774026,0.0711105465888977,0.132187373004854])
// Calculate the upper device's forward vector
var upperLegForwardVector = new THREE.Vector3( 0, 1, 0)  // V
upperLegForwardVector = upperLegForwardVector.applyMatrix4(upperLegRotMatrix)
// Calculate the lower device's forward vector in global space
var lowerLegForwardVector = new THREE.Vector3( 0, 1, 0 )  // V
lowerLegForwardVector = lowerLegForwardVector.applyMatrix4(lowerLegRotMatrix)
console.log("DOT PRODUCT " + upperLegForwardVector.dot(lowerLegForwardVector))
 var angle = Math.acos(upperLegForwardVector.dot(lowerLegForwardVector))
console.log("ANGLE " + angle)
 var theta = 180 - (THREE.Math.radToDeg(angle))
 console.log("FINAL " + theta)