FBX: support new color attributes, and sRGB/Linear/None colors option (T98721)

FBX exporter code was only supporting "Face Corner - Byte Color"
attribute type, using the deprecated Mesh.vertex_colors API. Update
the to use the new attributes API, and to handle all the attribute
combinations.

An option to pick between sRGB (default, matches current behavior),
Linear (requested in T82847) or None (don't export/import any color
attributes) has been added to the exporter and the importer.

Reviewed By: Bastien Montagne
Differential Revision: https://developer.blender.org/D15942

1 files changed, 22 insertions, 7 deletions

diff --git a/io_scene_fbx/export_fbx_bin.py b/io_scene_fbx/export_fbx_bin.py
index f560b19c..a4a96bf5 100644
--- a/io_scene_fbx/export_fbx_bin.py
+++ b/io_scene_fbx/export_fbx_bin.py
@@ -1111,14 +1111,20 @@ def fbx_data_mesh_elements(root, me_obj, scene_data, done_meshes):
         me.free_normals_split()
 
     # Write VertexColor Layers.
-    vcolnumber = len(me.vertex_colors)
+    colors_type = scene_data.settings.colors_type
+    vcolnumber = 0 if colors_type == 'NONE' else len(me.color_attributes)
     if vcolnumber:
         def _coltuples_gen(raw_cols):
             return zip(*(iter(raw_cols),) * 4)
 
-        t_lc = array.array(data_types.ARRAY_FLOAT64, (0.0,)) * len(me.loops) * 4
-        for colindex, collayer in enumerate(me.vertex_colors):
-            collayer.data.foreach_get("color", t_lc)
+        color_prop_name = "color_srgb" if colors_type == 'SRGB' else "color"
+
+        for colindex, collayer in enumerate(me.color_attributes):
+            is_point = collayer.domain == "POINT"
+            vcollen = len(me.vertices if is_point else me.loops)
+            t_lc = array.array(data_types.ARRAY_FLOAT64, (0.0,)) * vcollen * 4
+            collayer.data.foreach_get(color_prop_name, t_lc)
+
             lay_vcol = elem_data_single_int32(geom, b"LayerElementColor", colindex)
             elem_data_single_int32(lay_vcol, b"Version", FBX_GEOMETRY_VCOLOR_VERSION)
             elem_data_single_string_unicode(lay_vcol, b"Name", collayer.name)
@@ -1129,9 +1135,16 @@ def fbx_data_mesh_elements(root, me_obj, scene_data, done_meshes):
             elem_data_single_float64_array(lay_vcol, b"Colors", chain(*col2idx))  # Flatten again...
 
             col2idx = {col: idx for idx, col in enumerate(col2idx)}
-            elem_data_single_int32_array(lay_vcol, b"ColorIndex", (col2idx[c] for c in _coltuples_gen(t_lc)))
+            col_indices = list(col2idx[c] for c in _coltuples_gen(t_lc))
+            if is_point:
+                # for "point" domain colors, we could directly emit them
+                # with a "ByVertex" mapping type, but some software does not
+                # properly understand that. So expand to full "ByPolygonVertex"
+                # index map.
+                col_indices = list((col_indices[c.vertex_index] for c in me.loops))
+            elem_data_single_int32_array(lay_vcol, b"ColorIndex", col_indices)
             del col2idx
-        del t_lc
+            del t_lc
         del _coltuples_gen
 
     # Write UV layers.
@@ -3021,6 +3034,7 @@ def save_single(operator, scene, depsgraph, filepath="",
                 use_custom_props=False,
                 bake_space_transform=False,
                 armature_nodetype='NULL',
+                colors_type='SRGB',
                 **kwargs
                 ):
 
@@ -3088,7 +3102,7 @@ def save_single(operator, scene, depsgraph, filepath="",
         add_leaf_bones, bone_correction_matrix, bone_correction_matrix_inv,
         bake_anim, bake_anim_use_all_bones, bake_anim_use_nla_strips, bake_anim_use_all_actions,
         bake_anim_step, bake_anim_simplify_factor, bake_anim_force_startend_keying,
-        False, media_settings, use_custom_props,
+        False, media_settings, use_custom_props, colors_type,
     )
 
     import bpy_extras.io_utils
@@ -3155,6 +3169,7 @@ def defaults_unity3d():
         "use_mesh_modifiers_render": True,
         "use_mesh_edges": False,
         "mesh_smooth_type": 'FACE',
+        "colors_type": 'SRGB',
         "use_subsurf": False,
         "use_tspace": False,  # XXX Why? Unity is expected to support tspace import...
         "use_triangles": False,