A debugging tip

Figure 9.7: A table to help debug common viewpoint transform errors. Each $+$ means that the virtual world appears to move the correct way when performing the yaw, pitch, or roll. Each $-$ means it moves in the opposite way. The first case is correct. All others are bugs. ``L/R mix'' means that left and right-handed coordinate systems are getting mixed; the axis that was flipped is indicated.

Programmers often make mistakes when connecting the tracked orientation to the viewpoint. Figure 9.7 shows a table of the common mistakes. To determine whether the transform has been correctly applied, one should put on the headset and try rotating about the three canonical axes: A pure yaw, a pure pitch, and a pure roll. Let $+$ denote that the world is moving correctly with respect to a head rotation. Let $-$ denote that it seems to move in the opposite direction. Figure 9.7 shows a table of the eight possible outcomes and the most likely cause of each problem.