bin chunk は [1]。 field の順番を整理。GLB 仕様に関するコメントを追加。

Assets/UniGLTF/Runtime/UniGLTF/IO/GltfData.cs

@@ -1,6 +1,5 @@
 using System;
 using System.Collections.Generic;
-using System.Linq;
 
 namespace UniGLTF
 {
@@ -12,27 +11,33 @@ namespace UniGLTF
         /// </summary>
         public string TargetPath { get; }
 
-        /// <summary>
-        /// JSON source
-        /// </summary>
-        public string Json { get; }
-
-        /// <summary>
-        /// GLTF parsed from JSON
-        /// </summary>
-        public glTF GLTF { get; }
-
         /// <summary>
         /// Chunk Data.
         /// Maybe empty if source file was not glb format.
+        /// https://www.khronos.org/registry/glTF/specs/2.0/glTF-2.0.html#chunks
+        /// [0] must JSON
+        /// [1] must BIN
+        /// [2...] may exists.
         /// </summary>
         public IReadOnlyList<GlbChunk> Chunks { get; }
 
         /// <summary>
-        /// Bin chunk bytes
+        /// JSON chunk ToString
+        /// > This chunk MUST be the very first chunk of Binary glTF asset
+        /// </summary>
+        public string Json { get; }
+
+        /// <summary>
+        /// GLTF parsed from JSON chunk
+        /// </summary>
+        public glTF GLTF { get; }
+
+        /// <summary>
+        /// BIN chunk
+        /// > This chunk MUST be the second chunk of the Binary glTF asset
         /// </summary>
         /// <returns></returns>
-        public ArraySegment<byte> Bin => Chunks.First(x => x.ChunkType == GlbChunkType.BIN).Bytes;
+        public ArraySegment<byte> Bin => Chunks[1].Bytes;
 
         /// <summary>
         /// URI access