From 53e661378bae51240e7a4cb59227b99a882095bc Mon Sep 17 00:00:00 2001
From: Samuli Raivio <bqqbarbhg>
Date: Thu, 3 Oct 2019 15:12:53 +0200
Subject: Fix T70298: FBX IO: Apply squared crease transform when
 importing/exporting.

Blender maps crease sharpness from internal [0, 1] to OpenSubdiv's
[0, 10] by squaring the value (see `get_edge_sharpness()`).

Other software seems to treat FBX crease as linear times 10 using OpenSubdiv.

This commits attempts to make FBX exported by Blender consistent with the
results from FBX exported from Maya regarding crease intensity.

Differential Revision: https://developer.blender.org/D5930
---
 io_scene_fbx/__init__.py       | 2 +-
 io_scene_fbx/export_fbx_bin.py | 4 +++-
 io_scene_fbx/import_fbx.py     | 5 +++++
 3 files changed, 9 insertions(+), 2 deletions(-)

(limited to 'io_scene_fbx')

diff --git a/io_scene_fbx/__init__.py b/io_scene_fbx/__init__.py
index ec1afd09..7fdef2b0 100644
--- a/io_scene_fbx/__init__.py
+++ b/io_scene_fbx/__init__.py
@@ -21,7 +21,7 @@
 bl_info = {
     "name": "FBX format",
     "author": "Campbell Barton, Bastien Montagne, Jens Restemeier",
-    "version": (4, 17, 2),
+    "version": (4, 17, 3),
     "blender": (2, 81, 6),
     "location": "File > Import-Export",
     "description": "FBX IO meshes, UV's, vertex colors, materials, textures, cameras, lamps and actions",
diff --git a/io_scene_fbx/export_fbx_bin.py b/io_scene_fbx/export_fbx_bin.py
index e4d0feb3..b852adaa 100644
--- a/io_scene_fbx/export_fbx_bin.py
+++ b/io_scene_fbx/export_fbx_bin.py
@@ -1010,7 +1010,9 @@ def fbx_data_mesh_elements(root, me_obj, scene_data, done_meshes):
         for e in me.edges:
             if e.key not in edges_map:
                 continue  # Only loose edges, in theory!
-            t_ec[edges_map[e.key]] = e.crease
+            # Blender squares those values before sending them to OpenSubdiv, when other softwares don't,
+            # so we need to compensate that to get similar results through FBX...
+            t_ec[edges_map[e.key]] = e.crease * e.crease
 
         lay_crease = elem_data_single_int32(geom, b"LayerElementEdgeCrease", 0)
         elem_data_single_int32(lay_crease, b"Version", FBX_GEOMETRY_CREASE_VERSION)
diff --git a/io_scene_fbx/import_fbx.py b/io_scene_fbx/import_fbx.py
index 27e46076..9b8fbad1 100644
--- a/io_scene_fbx/import_fbx.py
+++ b/io_scene_fbx/import_fbx.py
@@ -1117,6 +1117,8 @@ def blen_read_geom_layer_smooth(fbx_obj, mesh):
         return False
 
 def blen_read_geom_layer_edge_crease(fbx_obj, mesh):
+    from math import sqrt
+
     fbx_layer = elem_find_first(fbx_obj, b'LayerElementEdgeCrease')
 
     if fbx_layer is None:
@@ -1151,6 +1153,9 @@ def blen_read_geom_layer_edge_crease(fbx_obj, mesh):
             fbx_layer_data, None,
             fbx_layer_mapping, fbx_layer_ref,
             1, 1, layer_id,
+            # Blender squares those values before sending them to OpenSubdiv, when other softwares don't,
+            # so we need to compensate that to get similar results through FBX...
+            xform=sqrt,
             )
     else:
         print("warning layer %r mapping type unsupported: %r" % (fbx_layer.id, fbx_layer_mapping))
-- 
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