function turnVectorArrayIntoNumberArray(arr){
  return flatten(arr.map(function(item){
    return [item.x, item.y, item.z];
  }));
}
Sets the x, y, and z component of the vector using two or three separate
variables, the data from a p5.Matrix, or the values from a float array.

@param {p5.Matrix|Array} [inMatrix] the input p5.Matrix or
                                    an Array of length 16