Maximum diffraction order [1, 8] - the number of 'bends' in a diffraction path. A high diffraction order accommodates more complex geometry at the expense of higher CPU usage. Diffraction must be enabled on the geometry to find diffraction paths (refer to AkGeometryParams). Set to 0 to disable diffraction on all geometry. This parameter limits the recursion depth of diffraction rays cast from the listener to scan the environment, and also the depth of the diffraction search to find paths between emitter and listener. To optimize CPU usage, set it to the maximum number of edges you expect the obstructing geometry to traverse. For example, if box-shaped geometry is used exclusively, and only a single box is expected between an emitter and then listener, limiting uMaxDiffractionOrder to 2 may be sufficient. A diffraction path search starts from the listener, so when the maximum diffraction order is exceeded, the remaining geometry between the end of the path and the emitter is ignored. In such case, where the search is terminated before reaching the emitter, the diffraction coefficient will be underestimated. It is calculated from a partial path, ignoring any remaining geometry.
AkSpatialAudio.h の 60 行目に定義があります。