glTF exporter: support KHR_materials_unlit

6 files changed, 206 insertions, 24 deletions

diff --git a/io_scene_gltf2/__init__.py b/io_scene_gltf2/__init__.py
index 3e09c58f..ab73a475 100755
--- a/io_scene_gltf2/__init__.py
+++ b/io_scene_gltf2/__init__.py
@@ -15,7 +15,7 @@
 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": (1, 4, 30),
+    "version": (1, 4, 31),
     'blender': (2, 90, 0),
     'location': 'File > Import-Export',
     'description': 'Import-Export as glTF 2.0',
diff --git a/io_scene_gltf2/blender/exp/gltf2_blender_gather_materials.py b/io_scene_gltf2/blender/exp/gltf2_blender_gather_materials.py
index c346a831..f1260940 100755
--- a/io_scene_gltf2/blender/exp/gltf2_blender_gather_materials.py
+++ b/io_scene_gltf2/blender/exp/gltf2_blender_gather_materials.py
@@ -21,6 +21,7 @@ from io_scene_gltf2.blender.exp import gltf2_blender_gather_texture_info, gltf2_
 from io_scene_gltf2.blender.exp import gltf2_blender_search_node_tree
 
 from io_scene_gltf2.blender.exp import gltf2_blender_gather_materials_pbr_metallic_roughness
+from io_scene_gltf2.blender.exp import gltf2_blender_gather_materials_unlit
 from ..com.gltf2_blender_extras import generate_extras
 from io_scene_gltf2.blender.exp import gltf2_blender_get
 from io_scene_gltf2.io.exp.gltf2_io_user_extensions import export_user_extensions
@@ -28,7 +29,7 @@ from io_scene_gltf2.io.com.gltf2_io_debug import print_console
 
 
 @cached
-def gather_material(blender_material, mesh_double_sided, export_settings):
+def gather_material(blender_material, export_settings):
     """
     Gather the material used by the blender primitive.
 
@@ -39,12 +40,16 @@ def gather_material(blender_material, mesh_double_sided, export_settings):
     if not __filter_material(blender_material, export_settings):
         return None
 
+    mat_unlit = __gather_material_unlit(blender_material, export_settings)
+    if mat_unlit is not None:
+        return mat_unlit
+
     orm_texture = __gather_orm_texture(blender_material, export_settings)
 
     material = gltf2_io.Material(
         alpha_cutoff=__gather_alpha_cutoff(blender_material, export_settings),
         alpha_mode=__gather_alpha_mode(blender_material, export_settings),
-        double_sided=__gather_double_sided(blender_material, mesh_double_sided, export_settings),
+        double_sided=__gather_double_sided(blender_material, export_settings),
         emissive_factor=__gather_emissive_factor(blender_material, export_settings),
         emissive_texture=__gather_emissive_texture(blender_material, export_settings),
         extensions=__gather_extensions(blender_material, export_settings),
@@ -92,8 +97,8 @@ def __gather_alpha_mode(blender_material, export_settings):
     return None
 
 
-def __gather_double_sided(blender_material, mesh_double_sided, export_settings):
-    if mesh_double_sided:
+def __gather_double_sided(blender_material, export_settings):
+    if not blender_material.use_backface_culling:
         return True
 
     old_double_sided_socket = gltf2_blender_get.get_socket_old(blender_material, "DoubleSided")
@@ -152,11 +157,6 @@ def __gather_emissive_texture(blender_material, export_settings):
 def __gather_extensions(blender_material, export_settings):
     extensions = {}
 
-    # KHR_materials_unlit
-
-    if gltf2_blender_get.get_socket(blender_material, "Background") is not None:
-        extensions["KHR_materials_unlit"] = Extension("KHR_materials_unlit", {}, False)
-
     # KHR_materials_clearcoat
 
     clearcoat_extension = __gather_clearcoat_extension(blender_material, export_settings)
@@ -351,3 +351,38 @@ def __gather_transmission_extension(blender_material, export_settings):
             transmission_extension['transmissionTexture'] = combined_texture
 
     return Extension('KHR_materials_transmission', transmission_extension, False)
+
+
+def __gather_material_unlit(blender_material, export_settings):
+    gltf2_unlit = gltf2_blender_gather_materials_unlit
+
+    info = gltf2_unlit.detect_shadeless_material(blender_material, export_settings)
+    if info is None:
+        return None
+
+    material = gltf2_io.Material(
+        alpha_cutoff=__gather_alpha_cutoff(blender_material, export_settings),
+        alpha_mode=__gather_alpha_mode(blender_material, export_settings),
+        double_sided=__gather_double_sided(blender_material, export_settings),
+        extensions={"KHR_materials_unlit": Extension("KHR_materials_unlit", {}, required=False)},
+        extras=__gather_extras(blender_material, export_settings),
+        name=__gather_name(blender_material, export_settings),
+        emissive_factor=None,
+        emissive_texture=None,
+        normal_texture=None,
+        occlusion_texture=None,
+
+        pbr_metallic_roughness=gltf2_io.MaterialPBRMetallicRoughness(
+            base_color_factor=gltf2_unlit.gather_base_color_factor(info, export_settings),
+            base_color_texture=gltf2_unlit.gather_base_color_texture(info, export_settings),
+            metallic_factor=0.0,
+            roughness_factor=0.9,
+            metallic_roughness_texture=None,
+            extensions=None,
+            extras=None,
+        )
+    )
+
+    export_user_extensions('gather_material_unlit_hook', export_settings, material, blender_material)
+
+    return material
diff --git a/io_scene_gltf2/blender/exp/gltf2_blender_gather_materials_pbr_metallic_roughness.py b/io_scene_gltf2/blender/exp/gltf2_blender_gather_materials_pbr_metallic_roughness.py
index a89b0ca1..a6a28fc4 100755
--- a/io_scene_gltf2/blender/exp/gltf2_blender_gather_materials_pbr_metallic_roughness.py
+++ b/io_scene_gltf2/blender/exp/gltf2_blender_gather_materials_pbr_metallic_roughness.py
@@ -61,8 +61,6 @@ def __gather_base_color_factor(blender_material, export_settings):
         base_color_socket = gltf2_blender_get.get_socket(blender_material, "BaseColor")
     if base_color_socket is None:
         base_color_socket = gltf2_blender_get.get_socket_old(blender_material, "BaseColorFactor")
-    if base_color_socket is None:
-        base_color_socket = gltf2_blender_get.get_socket(blender_material, "Background")
     if isinstance(base_color_socket, bpy.types.NodeSocket):
         rgb = gltf2_blender_get.get_factor_from_socket(base_color_socket, kind='RGB')
 
@@ -81,8 +79,6 @@ def __gather_base_color_texture(blender_material, export_settings):
         base_color_socket = gltf2_blender_get.get_socket(blender_material, "BaseColor")
     if base_color_socket is None:
         base_color_socket = gltf2_blender_get.get_socket_old(blender_material, "BaseColor")
-    if base_color_socket is None:
-        base_color_socket = gltf2_blender_get.get_socket(blender_material, "Background")
 
     alpha_socket = gltf2_blender_get.get_socket(blender_material, "Alpha")
     if alpha_socket is not None and alpha_socket.is_linked:
diff --git a/io_scene_gltf2/blender/exp/gltf2_blender_gather_materials_unlit.py b/io_scene_gltf2/blender/exp/gltf2_blender_gather_materials_unlit.py
new file mode 100644
index 00000000..b3012ea0
--- /dev/null
+++ b/io_scene_gltf2/blender/exp/gltf2_blender_gather_materials_unlit.py
@@ -0,0 +1,147 @@
+# Copyright 2018-2019 The glTF-Blender-IO authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from io_scene_gltf2.io.com import gltf2_io
+from io_scene_gltf2.blender.exp import gltf2_blender_gather_texture_info
+from io_scene_gltf2.blender.exp import gltf2_blender_get
+
+
+def detect_shadeless_material(blender_material, export_settings):
+    """Detect if this material is "shadeless" ie. should be exported
+    with KHR_materials_unlit. Returns None if not. Otherwise, returns
+    a dict with info from parsing the node tree.
+    """
+    if not blender_material.use_nodes: return None
+
+    # Old Background node detection (unlikely to happen)
+    bg_socket = gltf2_blender_get.get_socket(blender_material, "Background")
+    if bg_socket is not None:
+        return {'rgb_socket': bg_socket}
+
+    # Look for
+    # * any color socket, connected to...
+    # * optionally, the lightpath trick, connected to...
+    # * optionally, a mix-with-transparent (for alpha), connected to...
+    # * the output node
+
+    info = {}
+
+    for node in blender_material.node_tree.nodes:
+        if node.type == 'OUTPUT_MATERIAL':
+            socket = node.inputs[0]
+            break
+    else:
+        return None
+
+    # Be careful not to misidentify a lightpath trick as mix-alpha.
+    result = __detect_lightpath_trick(socket)
+    if result is not None:
+        socket = result['next_socket']
+    else:
+        result = __detect_mix_alpha(socket)
+        if result is not None:
+            socket = result['next_socket']
+            info['alpha_socket'] = result['alpha_socket']
+
+        result = __detect_lightpath_trick(socket)
+        if result is not None:
+            socket = result['next_socket']
+
+    # Check if a color socket, or connected to a color socket
+    if socket.type != 'RGBA':
+        from_socket = gltf2_blender_get.previous_socket(socket)
+        if from_socket is None: return None
+        if from_socket.type != 'RGBA': return None
+
+    info['rgb_socket'] = socket
+    return info
+
+
+def __detect_mix_alpha(socket):
+    # Detects this (used for an alpha hookup)
+    #
+    #                  [   Mix   ]
+    #  alpha_socket => [Factor   ] => socket
+    # [Transparent] => [Shader   ]
+    #   next_socket => [Shader   ]
+    #
+    # Returns None if not detected. Otherwise, a dict containing alpha_socket
+    # and next_socket.
+    prev = gltf2_blender_get.previous_node(socket)
+    if prev is None or prev.type != 'MIX_SHADER': return None
+    in1 = gltf2_blender_get.previous_node(prev.inputs[1])
+    if in1 is None or in1.type != 'BSDF_TRANSPARENT': return None
+    return {
+        'alpha_socket': prev.inputs[0],
+        'next_socket': prev.inputs[2],
+    }
+
+
+def __detect_lightpath_trick(socket):
+    # Detects this (used to prevent casting light on other objects) See ex.
+    # https://blender.stackexchange.com/a/21535/88681
+    #
+    #                 [   Lightpath  ]    [    Mix    ]
+    #                 [ Is Camera Ray] => [Factor     ] => socket
+    #                     (don't care) => [Shader     ]
+    #      next_socket => [ Emission ] => [Shader     ]
+    #
+    # The Emission node can be omitted.
+    # Returns None if not detected. Otherwise, a dict containing
+    # next_socket.
+    prev = gltf2_blender_get.previous_node(socket)
+    if prev is None or prev.type != 'MIX_SHADER': return None
+    in0 = gltf2_blender_get.previous_socket(prev.inputs[0])
+    if in0 is None or in0.node.type != 'LIGHT_PATH': return None
+    if in0.name != 'Is Camera Ray': return None
+    next_socket = prev.inputs[2]
+
+    # Detect emission
+    prev = gltf2_blender_get.previous_node(next_socket)
+    if prev is not None and prev.type == 'EMISSION':
+        next_socket = prev.inputs[0]
+
+    return {'next_socket': next_socket}
+
+
+def gather_base_color_factor(info, export_settings):
+    rgb, alpha = None, None
+
+    if 'rgb_socket' in info:
+        rgb = gltf2_blender_get.get_factor_from_socket(info['rgb_socket'], kind='RGB')
+    if 'alpha_socket' in info:
+        alpha = gltf2_blender_get.get_factor_from_socket(info['alpha_socket'], kind='VALUE')
+
+    if rgb is None: rgb = [1.0, 1.0, 1.0]
+    if alpha is None: alpha = 1.0
+
+    rgba = [*rgb, alpha]
+    if rgba == [1, 1, 1, 1]: return None
+    return rgba
+
+
+def gather_base_color_texture(info, export_settings):
+    sockets = (info.get('rgb_socket'), info.get('alpha_socket'))
+    sockets = tuple(s for s in sockets if s is not None)
+    if sockets:
+        # NOTE: separate RGB and Alpha textures will not get combined
+        # because gather_image determines how to pack images based on the
+        # names of sockets, and the names are hard-coded to a Principled
+        # style graph.
+        return gltf2_blender_gather_texture_info.gather_texture_info(
+            sockets[0],
+            sockets,
+            export_settings,
+        )
+    return None
diff --git a/io_scene_gltf2/blender/exp/gltf2_blender_gather_primitives.py b/io_scene_gltf2/blender/exp/gltf2_blender_gather_primitives.py
index fd325d48..a87a9db3 100755
--- a/io_scene_gltf2/blender/exp/gltf2_blender_gather_primitives.py
+++ b/io_scene_gltf2/blender/exp/gltf2_blender_gather_primitives.py
@@ -52,15 +52,12 @@ def gather_primitives(
 
     for internal_primitive in blender_primitives:
         material_idx = internal_primitive['material']
-        double_sided = False
         material = None
 
         if export_settings['gltf_materials'] == "EXPORT":
             try:
                 blender_material = bpy.data.materials[material_names[material_idx]]
-                double_sided = not blender_material.use_backface_culling
                 material = gltf2_blender_gather_materials.gather_material(blender_material,
-                                                                      double_sided,
                                                                       export_settings)
             except IndexError:
                 # no material at that index
diff --git a/io_scene_gltf2/blender/exp/gltf2_blender_get.py b/io_scene_gltf2/blender/exp/gltf2_blender_get.py
index 6a5152a6..58b835c0 100755
--- a/io_scene_gltf2/blender/exp/gltf2_blender_get.py
+++ b/io_scene_gltf2/blender/exp/gltf2_blender_get.py
@@ -231,7 +231,7 @@ def get_factor_from_socket(socket, kind):
     if fac is not None:
         return fac
 
-    node = __previous_node(socket)
+    node = previous_node(socket)
     if node is not None:
         x1, x2 = None, None
         if kind == 'RGB':
@@ -259,7 +259,7 @@ def get_const_from_socket(socket, kind):
             return socket.default_value
 
     # Handle connection to a constant RGB/Value node
-    prev_node = __previous_node(socket)
+    prev_node = previous_node(socket)
     if prev_node is not None:
         if kind == 'RGB' and prev_node.type == 'RGB':
             return list(prev_node.outputs[0].default_value)[:3]
@@ -269,16 +269,23 @@ def get_const_from_socket(socket, kind):
     return None
 
 
-def __previous_node(socket):
+def previous_socket(socket):
     while True:
         if not socket.is_linked:
             return None
 
-        node = socket.links[0].from_node
+        from_socket = socket.links[0].from_socket
 
         # Skip over reroute nodes
-        if node.type == 'REROUTE':
-            socket = node.inputs[0]
+        if from_socket.node.type == 'REROUTE':
+            socket = from_socket.node.inputs[0]
             continue
 
-        return node
+        return from_socket
+
+
+def previous_node(socket):
+    prev_socket = previous_socket(socket)
+    if prev_socket is not None:
+        return prev_socket.node
+    return None