Add traverse_transparent property to control sun light traversal through transparent objects

src/bonsai/bonsai/bim/module/light/prop.py

@@ -73,6 +73,8 @@ def update_sun_path_size(self, context):
 
 def update_display_shadows(self, context):
     if self.display_shadows:
+        if context.scene.BIMSolarProperties.traverse_transparent:
+            context.scene.BIMSolarProperties.traverse_transparent = False
         update_sun_path(self)
         context.scene.render.engine = "BLENDER_WORKBENCH"
         context.scene.display.shading.light = "FLAT"
@@ -86,6 +88,27 @@ def update_display_shadows(self, context):
         space = tool.Blender.get_view3d_space()
         space.shading.type = "SOLID"
 
+def update_traverse_transparent(self, context):
+    if self.traverse_transparent:
+        if context.scene.BIMSolarProperties.display_shadows:
+            context.scene.BIMSolarProperties.display_shadows = False
+        if context.scene.sun_pos_properties.sun_object is None:
+            bpy.ops.object.light_add(type="SUN", radius=1, align="WORLD", location=(0, 0, 0), scale=(1, 1, 1))
+            bpy.ops.object.move_to_collection(collection_index=0)
+            context.scene.sun_pos_properties.sun_object = bpy.context.active_object
+        update_sun_path(self)
+        context.scene.render.engine = "BLENDER_EEVEE_NEXT"
+        context.scene.display.shading.light = "FLAT"
+        context.scene.display.shading.show_shadows = True
+        context.scene.display.shading.show_object_outline = True
+        context.scene.display.shadow_focus = 1.0
+        context.scene.view_settings.view_transform = "Standard"  # Preserve shading colours
+        space = tool.Blender.get_view3d_space()
+        space.shading.type = "RENDERED"
+    else:
+        context.scene.render.engine = "BLENDER_WORKBENCH"
+        space = tool.Blender.get_view3d_space()
+        space.shading.type = "SOLID"
 
 def update_display_sun_path(self, context):
     if self.display_sun_path:
@@ -400,6 +423,14 @@ class BIMSolarProperties(PropertyGroup):
         description="Enables a visual style to display shadows easily",
         update=update_display_shadows,
     )
+
+    traverse_transparent: BoolProperty(
+        name="Enable Sun: Shadows and Light traversal of transparent objects",
+        default=False,
+        description="Enables a visual style so Sun light can traverse transparent objects and cast shadows (it toggles the render engine to EEVEE)",
+        update=update_traverse_transparent,
+    )
+
     display_sun_path: BoolProperty(
         name="Display Sun Path",
         default=False,

src/bonsai/bonsai/bim/module/light/ui.py

@@ -239,5 +239,11 @@ class BIM_PT_solar(bpy.types.Panel):
         row.prop(props, "display_shadows", icon="SHADING_RENDERED")
         row.prop(context.scene.display.shading, "shadow_intensity", text="Shadow Intensity")
 
+        row = self.layout.row(align=True)
+        row.prop(props, "traverse_transparent", icon="SHADING_RENDERED")
+        if props.traverse_transparent:
+            row = self.layout.row(align=True)
+            row.prop(context.scene.sun_pos_properties.sun_object.data , "energy", text="Sun Intensity")
+
         row = self.layout.row(align=True)
         row.operator("bim.view_from_sun", icon="LIGHT_HEMI")