-# FIND_NORMALS[=n] pre-compute vertex normals at loading time
-# set to 1 for per-face normals, 2 for averaged normals
+# PRE_NORMALS[=n] pre-compute mesh normals at scene-loading time;
+# set to 1 for per-face normals, 2 for averaged normals,
+# or 3 to also enable caching the computed normals