Added support for standalone metalness and roughness textures

Users now have another option to plug metalness and roughness textures into the corresponding channels, aside from using the same texture and separate RGB

io_ogre/ogre/materialv2json.py

@@ -188,6 +188,12 @@ def generate_pbs_datablock(self, material):
         }
         if tex_filename:
             datablock["metalness"]["texture"] = os.path.split(tex_filename)[-1]
+            datablock["metalness"]["value"] = 0.818  # default mtallic value according to the docs
+        else:  # Support for standalone metallic texture
+            tex_filename = self.prepare_texture(bsdf.metallic_texture)[0]
+            if tex_filename:
+                datablock["metalness"]["texture"] = os.path.split(tex_filename)[-1]
+                datablock["metalness"]["value"] = 0.818
 
         # Set up normalmap parameters, only if texture is present
         tex_filename = self.prepare_texture(bsdf.normalmap_texture)[0]
@@ -206,6 +212,12 @@ def generate_pbs_datablock(self, material):
         }
         if tex_filename:
             datablock["roughness"]["texture"] = os.path.split(tex_filename)[-1]
+            datablock["roughness"]["value"] = 1.0 # default roughness value according to the docs
+        else:  # Support for standalone roughness texture
+            tex_filename = self.prepare_texture(bsdf.roughness_texture)[0]
+            if tex_filename:
+                datablock["roughness"]["texture"] = os.path.split(tex_filename)[-1]
+                datablock["roughness"]["value"] = 1.0
 
         # Set up specular parameters
         logger.debug("Specular params")