if (inVector.equals(outVector)) { //TODO: allow for some small difference?
cutVector = outVector.rightNormal();
} else {
cutVector = outVector.subtract(inVector);
cutVector = cutVector.normalize();
}
//make sure that cutVector points to the right, which is equivalent to:
//y component of the cross product (inVector x cutVector) is positive.
//If this isn't the case, invert the cut vector.