io_scene_gltf2/blender/exp/material/gltf2_blender_gather_materials_unlit.py

   1 # SPDX-FileCopyrightText: 2018-2022 The glTF-Blender-IO authors
   2 #
   3 # SPDX-License-Identifier: Apache-2.0
   4
   5 from ....io.com.gltf2_io_extensions import Extension
   6 from ...exp import gltf2_blender_get
   7 from . import gltf2_blender_gather_texture_info
   8
   9 def detect_shadeless_material(blender_material, export_settings):
  10     """Detect if this material is "shadeless" ie. should be exported
  11     with KHR_materials_unlit. Returns None if not. Otherwise, returns
  12     a dict with info from parsing the node tree.
  13     """
  14     if not blender_material.use_nodes: return None
  15
  16     # Old Background node detection (unlikely to happen)
  17     bg_socket = gltf2_blender_get.get_socket(blender_material, "Background")
  18     if bg_socket is not None:
  19         return {'rgb_socket': bg_socket}
  20
  21     # Look for
  22     # * any color socket, connected to...
  23     # * optionally, the lightpath trick, connected to...
  24     # * optionally, a mix-with-transparent (for alpha), connected to...
  25     # * the output node
  26
  27     info = {}
  28
  29     for node in blender_material.node_tree.nodes:
  30         if node.type == 'OUTPUT_MATERIAL' and node.is_active_output:
  31             socket = node.inputs[0]
  32             break
  33     else:
  34         return None
  35
  36     # Be careful not to misidentify a lightpath trick as mix-alpha.
  37     result = __detect_lightpath_trick(socket)
  38     if result is not None:
  39         socket = result['next_socket']
  40     else:
  41         result = __detect_mix_alpha(socket)
  42         if result is not None:
  43             socket = result['next_socket']
  44             info['alpha_socket'] = result['alpha_socket']
  45
  46         result = __detect_lightpath_trick(socket)
  47         if result is not None:
  48             socket = result['next_socket']
  49
  50     # Check if a color socket, or connected to a color socket
  51     if socket.type != 'RGBA':
  52         from_socket = gltf2_blender_get.previous_socket(socket)
  53         if from_socket is None: return None
  54         if from_socket.type != 'RGBA': return None
  55
  56     info['rgb_socket'] = socket
  57     return info
  58
  59
  60 def __detect_mix_alpha(socket):
  61     # Detects this (used for an alpha hookup)
  62     #
  63     #                  [   Mix   ]
  64     #  alpha_socket => [Factor   ] => socket
  65     # [Transparent] => [Shader   ]
  66     #   next_socket => [Shader   ]
  67     #
  68     # Returns None if not detected. Otherwise, a dict containing alpha_socket
  69     # and next_socket.
  70     prev = gltf2_blender_get.previous_node(socket)
  71     if prev is None or prev.type != 'MIX_SHADER': return None
  72     in1 = gltf2_blender_get.previous_node(prev.inputs[1])
  73     if in1 is None or in1.type != 'BSDF_TRANSPARENT': return None
  74     return {
  75         'alpha_socket': prev.inputs[0],
  76         'next_socket': prev.inputs[2],
  77     }
  78
  79
  80 def __detect_lightpath_trick(socket):
  81     # Detects this (used to prevent casting light on other objects) See ex.
  82     # https://blender.stackexchange.com/a/21535/88681
  83     #
  84     #                 [   Lightpath  ]    [    Mix    ]
  85     #                 [ Is Camera Ray] => [Factor     ] => socket
  86     #                     (don't care) => [Shader     ]
  87     #      next_socket => [ Emission ] => [Shader     ]
  88     #
  89     # The Emission node can be omitted.
  90     # Returns None if not detected. Otherwise, a dict containing
  91     # next_socket.
  92     prev = gltf2_blender_get.previous_node(socket)
  93     if prev is None or prev.type != 'MIX_SHADER': return None
  94     in0 = gltf2_blender_get.previous_socket(prev.inputs[0])
  95     if in0 is None or in0.node.type != 'LIGHT_PATH': return None
  96     if in0.name != 'Is Camera Ray': return None
  97     next_socket = prev.inputs[2]
  98
  99     # Detect emission
 100     prev = gltf2_blender_get.previous_node(next_socket)
 101     if prev is not None and prev.type == 'EMISSION':
 102         next_socket = prev.inputs[0]
 103
 104     return {'next_socket': next_socket}
 105
 106
 107 def gather_base_color_factor(info, export_settings):
 108     rgb, alpha = None, None
 109
 110     if 'rgb_socket' in info:
 111         rgb = gltf2_blender_get.get_factor_from_socket(info['rgb_socket'], kind='RGB')
 112     if 'alpha_socket' in info:
 113         alpha = gltf2_blender_get.get_factor_from_socket(info['alpha_socket'], kind='VALUE')
 114
 115     if rgb is None: rgb = [1.0, 1.0, 1.0]
 116     if alpha is None: alpha = 1.0
 117
 118     rgba = [*rgb, alpha]
 119     if rgba == [1, 1, 1, 1]: return None
 120     return rgba
 121
 122
 123 def gather_base_color_texture(info, export_settings):
 124     sockets = (info.get('rgb_socket'), info.get('alpha_socket'))
 125     sockets = tuple(s for s in sockets if s is not None)
 126     if sockets:
 127         # NOTE: separate RGB and Alpha textures will not get combined
 128         # because gather_image determines how to pack images based on the
 129         # names of sockets, and the names are hard-coded to a Principled
 130         # style graph.
 131         unlit_texture, unlit_use_active_uvmap, _ = gltf2_blender_gather_texture_info.gather_texture_info(
 132             sockets[0],
 133             sockets,
 134             (),
 135             export_settings,
 136         )
 137         return unlit_texture, ["unlitTexture"] if unlit_use_active_uvmap else None
 138     return None, None