glTF exporter: fix PBR values when emission node is used

io_scene_gltf2/__init__.py

@@ -4,7 +4,7 @@
 bl_info = {
     'name': 'glTF 2.0 format',
     'author': 'Julien Duroure, Scurest, Norbert Nopper, Urs Hanselmann, Moritz Becher, Benjamin Schmithüsen, Jim Eckerlein, and many external contributors',
-    "version": (3, 2, 8),
+    "version": (3, 2, 9),
     'blender': (3, 1, 0),
     'location': 'File > Import-Export',
     'description': 'Import-Export as glTF 2.0',

io_scene_gltf2/blender/exp/gltf2_blender_gather_materials.py

@@ -55,6 +55,12 @@ def gather_material(blender_material, export_settings):
         pbr_metallic_roughness=__gather_pbr_metallic_roughness(blender_material, orm_texture, export_settings)
     )
 
+    # If emissive is set, from an emissive node (not PBR)
+    # We need to set manually default values for 
+    # pbr_metallic_roughness.baseColor
+    if material.emissive_factor is not None and gltf2_blender_get.get_node_socket(blender_material, bpy.types.ShaderNodeBsdfPrincipled, "Base Color") is None:
+        material.pbr_metallic_roughness = gltf2_blender_gather_materials_pbr_metallic_roughness.get_default_pbr_for_emissive_node()
+
     export_user_extensions('gather_material_hook', export_settings, material, blender_material)
 
     return material

io_scene_gltf2/blender/exp/gltf2_blender_gather_materials_pbr_metallic_roughness.py

@@ -153,3 +153,14 @@ def __has_image_node_from_socket(socket):
     if not result:
         return False
     return True
+
+def get_default_pbr_for_emissive_node():
+    return gltf2_io.MaterialPBRMetallicRoughness(
+        base_color_factor=[0.0,0.0,0.0,1.0],
+        base_color_texture=None,
+        extensions=None,
+        extras=None,
+        metallic_factor=None,
+        metallic_roughness_texture=None,
+        roughness_factor=None
+    )

io_scene_gltf2/blender/exp/gltf2_blender_get.py

@@ -32,6 +32,21 @@ def get_object_from_datapath(blender_object, data_path: str):
     return prop
 
 
+def get_node_socket(blender_material, type, name):
+    """
+    For a given material input name, retrieve the corresponding node tree socket for a given node type.
+
+    :param blender_material: a blender material for which to get the socket
+    :return: a blender NodeSocket for a given type
+    """
+    nodes = [n for n in blender_material.node_tree.nodes if isinstance(n, type) and not n.mute]
+    nodes = [node for node in nodes if check_if_is_linked_to_active_output(node.outputs[0])]
+    inputs = sum([[input for input in node.inputs if input.name == name] for node in nodes], [])
+    if inputs:
+        return inputs[0]
+    return None
+
+
 def get_socket(blender_material: bpy.types.Material, name: str):
     """
     For a given material input name, retrieve the corresponding node tree socket.
@@ -46,13 +61,9 @@ def get_socket(blender_material: bpy.types.Material, name: str):
         if name == "Emissive":
             # Check for a dedicated Emission node first, it must supersede the newer built-in one
             # because the newer one is always present in all Principled BSDF materials.
-            type = bpy.types.ShaderNodeEmission
-            name = "Color"
-            nodes = [n for n in blender_material.node_tree.nodes if isinstance(n, type) and not n.mute]
-            nodes = [node for node in nodes if check_if_is_linked_to_active_output(node.outputs[0])]
-            inputs = sum([[input for input in node.inputs if input.name == name] for node in nodes], [])
-            if inputs:
-                return inputs[0]
+            emissive_socket = get_node_socket(blender_material, bpy.types.ShaderNodeEmission, "Color")
+            if emissive_socket:
+                return emissive_socket
             # If a dedicated Emission node was not found, fall back to the Principled BSDF Emission socket.
             name = "Emission"
             type = bpy.types.ShaderNodeBsdfPrincipled
@@ -61,11 +72,8 @@ def get_socket(blender_material: bpy.types.Material, name: str):
             name = "Color"
         else:
             type = bpy.types.ShaderNodeBsdfPrincipled
-        nodes = [n for n in blender_material.node_tree.nodes if isinstance(n, type) and not n.mute]
-        nodes = [node for node in nodes if check_if_is_linked_to_active_output(node.outputs[0])]
-        inputs = sum([[input for input in node.inputs if input.name == name] for node in nodes], [])
-        if inputs:
-            return inputs[0]
+        
+        return get_node_socket(blender_material, type, name)
 
     return None