glTF exporter: Fix division by zero when IOR is 1.0

io_scene_gltf2/__init__.py

@@ -4,7 +4,7 @@
 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": (3, 4, 32),
+    "version": (3, 4, 33),
     'blender': (3, 3, 0),
     'location': 'File > Import-Export',
     'description': 'Import-Export as glTF 2.0',

io_scene_gltf2/blender/exp/gltf2_blender_gather_materials_specular.py

@@ -120,9 +120,13 @@ def export_specular(blender_material, export_settings):
                 return np.array([c[0] / l, c[1] / l, c[2] / l])            
 
             f0_from_ior = ((ior - 1)/(ior + 1))**2
-            tint_strength = (1 - specular_tint) + normalize(base_color) * specular_tint
-            specular_color = (1 - transmission) * (1 / f0_from_ior) * 0.08 * specular * tint_strength + transmission * tint_strength
-            specular_extension['specularColorFactor'] = list(specular_color)
+            if f0_from_ior == 0:
+                specular_color = [1.0, 1.0, 1.0]
+            else:
+                tint_strength = (1 - specular_tint) + normalize(base_color) * specular_tint
+                specular_color = (1 - transmission) * (1 / f0_from_ior) * 0.08 * specular * tint_strength + transmission * tint_strength
+                specular_color = list(specular_color)
+            specular_extension['specularColorFactor'] = specular_color
     else:
         if specular_not_linked and specular == BLENDER_SPECULAR and specular_tint_not_linked and specular_tint == BLENDER_SPECULAR_TINT:
             return None, None