Dealing with the Ill-Conditioned Equations of Motion for Articulated Figures The paper discusses some of the challenges in designing an IK solver. The authors describe Singular Value Decomposition which carefully chooses the appropriate coordinate systems to reach the main system of equations we need to solve. Our goals are minimizing our deviation, and the amount of rotations needed by joints. . The paper also explains the effect of error in measurement. If we can accept some error on the end results, how does this translate to conditions in the joint space. The worst cases happen, when it is very easy to move in one direction, but very hard to move in the other (for example, if all the joints are totally stretched out). Finally the paper explains the "damped least square error" method to actually solve the problem.