node_wrangler/operators.py

@@ -491,6 +491,7 @@ class NWPreviewNode(Operator, NWBase):
     def __init__(self):
         self.shader_output_type = ""
         self.shader_output_ident = ""
+        self.shader_viewer_ident = ""
 
     @classmethod
     def poll(cls, context):
@@ -513,10 +514,12 @@ class NWPreviewNode(Operator, NWBase):
             else:
                 self.shader_output_type = "OUTPUT_MATERIAL"
                 self.shader_output_ident = "ShaderNodeOutputMaterial"
+            self.shader_viewer_ident = "ShaderNodeEmission"
 
         elif shader_type == 'WORLD':
             self.shader_output_type = "OUTPUT_WORLD"
             self.shader_output_ident = "ShaderNodeOutputWorld"
+            self.shader_viewer_ident = "ShaderNodeBackground"
 
     def ensure_viewer_socket(self, node_tree, socket_type, connect_socket=None):
         """Check if a viewer output already exists in a node group, otherwise create it"""
@@ -559,6 +562,44 @@ class NWPreviewNode(Operator, NWBase):
             groupout.is_active_output = True
         return groupout
 
+    @staticmethod
+    def get_scene_intensity(context):
+        """Calculate intensity compensation based on scene exposure"""
+        intensity = 1.0
+        if context.scene.render.engine == 'CYCLES' and hasattr(context.scene, 'cycles'):
+            # Film exposure is a multiplier
+            intensity /= context.scene.cycles.film_exposure
+        # CM exposure is measured in stops/EVs (2^x)
+        intensity /= 2.0 ** context.scene.view_settings.exposure
+        return intensity
+
+    @staticmethod
+    def get_emission_node(base_node_tree):
+        for node in base_node_tree.nodes:
+            if "Emission Viewer" in node.name:
+                return node
+
+    def ensure_emission_node(self, context, base_node_tree, output_node):
+        emission_node = self.get_emission_node(base_node_tree)
+        if emission_node is None:
+            emission_node = base_node_tree.nodes.new(self.shader_viewer_ident)
+            emission_node.hide = True
+            emission_node.location = output_node.location + Vector((0, 40))
+            emission_node.label = "Viewer"
+            emission_node.name = "Emission Viewer"
+            emission_node.use_custom_color = True
+            emission_node.color = (0.6, 0.5, 0.4)
+            emission_node.select = False
+
+        # If Viewer is connected to output by user, don't change those connections (patch by gandalf3)
+        if (len(emission_node.outputs[0].links) == 0
+                or emission_node.outputs[0].links[0].to_node != output_node):
+            connect_sockets(emission_node.outputs[0], output_node.inputs[0])
+
+        # Set brightness of viewer to compensate for Film and CM exposure
+        emission_node.inputs[1].default_value = self.get_scene_intensity(context)
+        return emission_node
+
     @classmethod
     def search_sockets(cls, node, sockets, index=None):
         """Recursively scan nodes for viewer sockets and store them in a list"""
@@ -759,11 +800,24 @@ class NWPreviewNode(Operator, NWBase):
             active_node_socket_index = self.get_output_index(
                 active, output_node, base_node_tree == active_tree, 'SHADER'
             )
-            if active.outputs[active_node_socket_index].name == "Volume":
+
+            node_output = active.outputs[active_node_socket_index]
+            if node_output.name == "Volume":
                 output_node_socket_index = 1
             else:
                 output_node_socket_index = 0
 
+                # Use an emission node if needed to compensate for scene exposure
+                settings = context.preferences.addons[__package__].preferences
+                if (settings.use_viewer_exposure_compensation
+                        and self.get_scene_intensity(context) != 1.0
+                        and node_output.type != 'SHADER'):
+                    output_node = self.ensure_emission_node(context, base_node_tree, output_node)
+                    output_node_socket_index = 0
+                else:
+                    if (emission_node := self.get_emission_node(base_node_tree)) is not None:
+                        base_node_tree.nodes.remove(emission_node)
+
         # If there are no nested node groups, the link starts at the active node
         node_output = active.outputs[active_node_socket_index]
         if len(path) > 1:

node_wrangler/preferences.py

@@ -85,6 +85,11 @@ class NWNodeWrangler(bpy.types.AddonPreferences):
         ),
         default='CENTER',
         description="When merging nodes with the Ctrl+Numpad0 hotkey (and similar) specify the position of the new nodes")
+    use_viewer_exposure_compensation: BoolProperty(
+        name="Use Viewer Exposure Compensation",
+        default=False,
+        description="When using the viewer to preview colors in the shader editor, take the scene exposure into account to display the original color"
+    )
 
     show_hotkey_list: BoolProperty(
         name="Show Hotkey List",
@@ -109,6 +114,7 @@ class NWNodeWrangler(bpy.types.AddonPreferences):
         col = layout.column()
         col.prop(self, "merge_position")
         col.prop(self, "merge_hide")
+        col.prop(self, "use_viewer_exposure_compensation")
 
         box = layout.box()
         col = box.column(align=True)