Use proper area light conversion factor depending on blender version

Author: bathal1

mitsuba-blender/io/exporter/lights.py

@@ -1,6 +1,7 @@
 from mathutils import Matrix
 import numpy as np
 from .export_context import Files
+import bpy
 
 def convert_area_light(b_light, export_ctx):
     params = {}
@@ -43,8 +44,11 @@ def convert_area_light(b_light, export_ctx):
     emitter = {
         'type': 'area'
     }
-    # Conversion factor used in Cycles, to convert to irradiance (don't ask me why)
-    conv_fac = 1.0 / (area * 4.0)
+    # Conversion factor used in Cycles
+    if bpy.app.version < (4, 0, 0):
+        conv_fac = 1.0 / (area * 4.0)
+    else:
+        conv_fac = 1.0 / (area * np.pi)
     emitter['radiance'] = export_ctx.spectrum(conv_fac * b_light.data.energy * b_light.data.color)
     params['emitter'] = emitter