mesh files use game space (right-handed, y up): obj/gltf import and export no longer mirror models, per-mesh handedness keeps meshes of old projects as they were, python tools follow (--export-space for the old files)

tools/geomlib.py

@@ -13,6 +13,24 @@ FUN_0042ac50 MAP, FUN_00406d30 texture table, FUN_00556510 tile renderer).
 import math
 import struct
 
+# ---------------------------------------------------------------- OBJ file space
+# OBJ files (geom_export/geom_import/geom_demo, the editor's Import mesh and OBJ/glTF export) are
+# right-handed, y up, in game space: file (x, y, z) = export (x, y, -z). The game shows export space
+# left-handed, so this is how Blender shows the level the same way round as the game. Converting
+# mirrors, so the corner order reverses (first corner kept: export (0,1,2) <-> file (0,2,1)).
+
+
+def to_file(p):
+    """Export-space point -> OBJ file point."""
+    return (p[0], p[1], -p[2])
+
+
+def file_order(seq):
+    """Corner order export <-> file (an involution)."""
+    seq = list(seq)
+    return seq[:1] + seq[:0:-1]
+
+
 # ---------------------------------------------------------------- WAD