diff --git a/Assets/UniGLTF/Runtime/UniGLTF/IO/TextureConverter/MetallicRoughnessConverter.cs b/Assets/UniGLTF/Runtime/UniGLTF/IO/TextureConverter/MetallicRoughnessConverter.cs
index 4f6a9ad90..ee078b880 100644
--- a/Assets/UniGLTF/Runtime/UniGLTF/IO/TextureConverter/MetallicRoughnessConverter.cs
+++ b/Assets/UniGLTF/Runtime/UniGLTF/IO/TextureConverter/MetallicRoughnessConverter.cs
@@ -1,14 +1,27 @@
+#define SIMPLE_CONV
 using UnityEngine;
 
 namespace UniGLTF
 {
+    /// <summary>
+    /// 
+    /// * https://github.com/dwango/UniVRM/issues/212.
+    /// * https://blogs.unity3d.com/jp/2016/01/25/ggx-in-unity-5-3/  
+    /// * https://github.com/vrm-c/UniVRM/issues/388
+    /// 
+    /// Occlusion(glTF): src.r
+    /// Roughness(glTF): src.g -> Smoothness(Unity): dst.a (bake smoothnessOrRoughness)
+    /// Metallic(glTF) : src.b -> Metallic(Unity)  : dst.r
+    /// </summary>
     public class MetallicRoughnessConverter : ITextureConverter
     {
-        private float _smoothnessOrRoughness;
+        private readonly float _smoothnessOrRoughness;
+        private readonly float _smoothnessOrRoughnessInverse;
 
         public MetallicRoughnessConverter(float smoothnessOrRoughness)
         {
             _smoothnessOrRoughness = smoothnessOrRoughness;
+            _smoothnessOrRoughnessInverse = 1.0f / _smoothnessOrRoughness;
         }
 
         public Texture2D GetImportTexture(Texture2D texture)
@@ -25,43 +38,45 @@ namespace UniGLTF
 
         public Color32 Import(Color32 src)
         {
-            // Roughness(glTF): dst.g -> Smoothness(Unity): src.a (with conversion)
-            // Metallic(glTF) : dst.b -> Metallic(Unity)  : src.r
-
-            var pixelRoughnessFactor = (src.g * _smoothnessOrRoughness) / 255.0f; // roughness
-            var pixelSmoothness = 1.0f - Mathf.Sqrt(pixelRoughnessFactor);
-
-            return new Color32
+            var dst = new Color32
             {
                 r = src.b,
                 g = 0,
                 b = 0,
-                // Bake roughness values into a texture.
-                // See: https://github.com/dwango/UniVRM/issues/212.
-                a = (byte)Mathf.Clamp(pixelSmoothness * 255, 0, 255),
             };
+
+            // Bake _smoothnessOrRoughness into a texture.
+#if SIMPLE_CONV
+            dst.a = (byte)(255 - src.g * _smoothnessOrRoughness);
+#else
+            var pixelRoughnessFactor = (src.g * _smoothnessOrRoughness) / 255.0f; // roughness
+            var pixelSmoothness = 1.0f - Mathf.Sqrt(pixelRoughnessFactor);
+            dst.a = (byte)Mathf.Clamp(pixelSmoothness * 255, 0, 255);
+#endif
+            return dst;
         }
 
         public Color32 Export(Color32 src)
         {
-            // Smoothness(Unity): src.a -> Roughness(glTF): dst.g (with conversion)
-            // Metallic(Unity)  : src.r -> Metallic(glTF) : dst.b
 
-            var pixelSmoothness = (src.a * _smoothnessOrRoughness) / 255.0f; // smoothness
-            // https://blogs.unity3d.com/jp/2016/01/25/ggx-in-unity-5-3/
-            var pixelRoughnessFactorSqrt = (1.0f - pixelSmoothness);
-            var pixelRoughnessFactor = pixelRoughnessFactorSqrt * pixelRoughnessFactorSqrt;
-
-            return new Color32
+            var dst = new Color32
             {
                 r = 0,
-                // Bake smoothness values into a texture.
-                // See: https://github.com/dwango/UniVRM/issues/212.
-                g = (byte)Mathf.Clamp(pixelRoughnessFactor * 255, 0, 255),
                 b = src.r,
                 a = 255,
             };
+
+            // Bake divide _smoothnessOrRoughness from a texture.
+#if SIMPLE_CONV
+            dst.g = (byte)(255 - src.a);
+#else                
+            var pixelSmoothness = (src.a * _smoothnessOrRoughness) / 255.0f; // smoothness
+            var pixelRoughnessFactorSqrt = (1.0f - pixelSmoothness);
+            var pixelRoughnessFactor = pixelRoughnessFactorSqrt * pixelRoughnessFactorSqrt;
+            dst.g = (byte)Mathf.Clamp(pixelRoughnessFactor * 255, 0, 255);
+#endif                
+
+            return dst;
         }
     }
-
 }