Geologists and engineers calculate normal and shear stress from the orientation and magnitude of two of the three principal stresses using the Mohr diagram. This diagram graphically illustrates in two dimensions the complex mathematical relationships between the components that make up a traction. Software for graphing the Mohr diagram is provided in Visualizing Stress. However, before using the software to analyze various states of stress, the components that make up the Mohr diagram must be explored.