Merge pull request #37 from B3zaleel/implement-MSFT_packing_occlusion…

…RoughnessMetallic-extension

Implement MSFT_packing_occlusionRoughnessMetallic Gltf extension

src/ThreeDModels/Format/Gltf/Extensions/MSFT_packing_occlusionRoughnessMetallic.cs

@@ -0,0 +1,143 @@
+using System.Text.Json;
+using ThreeDModels.Format.Gltf.Elements;
+using ThreeDModels.Format.Gltf.IO;
+using static ThreeDModels.Format.Gltf.IO.Utf8JsonReaderHelpers;
+
+namespace ThreeDModels.Format.Gltf.Extensions;
+
+/// <summary>
+/// Represents an object that specifies a packing of occlusion, roughness, and metallic in a single texture and a two channel normal map.
+/// </summary>
+public class MSFT_packing_occlusionRoughnessMetallic : IGltfProperty
+{
+    /// <summary>
+    /// A texture with packing Occlusion (R), Roughness (G), Metallic (B).
+    /// </summary>
+    public MsftTextureIndex? OcclusionRoughnessMetallicTexture { get; set; }
+    /// <summary>
+    /// A texture with packing Roughness (R), Metallic (G), Occlusion (B).
+    /// </summary>
+    public MsftTextureIndex? RoughnessMetallicOcclusionTexture { get; set; }
+    /// <summary>
+    /// A texture which contains two channel (RG) normal map.
+    /// </summary>
+    public MsftTextureIndex? NormalTexture { get; set; }
+    public Dictionary<string, object?>? Extensions { get; set; }
+    public object? Extras { get; set; }
+}
+
+public class MsftTextureIndex
+{
+    /// <summary>
+    /// The index of the texture.
+    /// </summary>
+    public int? Index { get; set; }
+}
+
+public class MsftPackingOcclusionRoughnessMetallicExtension : IGltfExtension
+{
+    public string Name => nameof(MSFT_packing_occlusionRoughnessMetallic);
+
+    public object? Read(ref Utf8JsonReader jsonReader, GltfReaderContext context, Type parentType)
+    {
+        if (parentType != typeof(Gltf))
+        {
+            throw new InvalidDataException("MSFT_packing_occlusionRoughnessMetallic must be used in a Gltf root.");
+        }
+        MsftTextureIndex? occlusionRoughnessMetallicTexture = null;
+        MsftTextureIndex? roughnessMetallicOcclusionTexture = null;
+        MsftTextureIndex? normalTexture = null;
+        Dictionary<string, object?>? extensions = null;
+        object? extras = null;
+        if (jsonReader.TokenType == JsonTokenType.PropertyName && jsonReader.Read())
+        {
+        }
+        if (jsonReader.TokenType == JsonTokenType.Null)
+        {
+            return null;
+        }
+        else if (jsonReader.TokenType != JsonTokenType.StartObject)
+        {
+            throw new InvalidDataException("Failed to find start of property.");
+        }
+        while (jsonReader.Read())
+        {
+            if (jsonReader.TokenType == JsonTokenType.EndObject)
+            {
+                break;
+            }
+            var propertyName = jsonReader.GetString();
+            if (propertyName == nameof(occlusionRoughnessMetallicTexture))
+            {
+                occlusionRoughnessMetallicTexture = MsftTextureIndexSerialization.Read(ref jsonReader, context);
+            }
+            else if (propertyName == nameof(roughnessMetallicOcclusionTexture))
+            {
+                roughnessMetallicOcclusionTexture = MsftTextureIndexSerialization.Read(ref jsonReader, context);
+            }
+            else if (propertyName == nameof(normalTexture))
+            {
+                normalTexture = MsftTextureIndexSerialization.Read(ref jsonReader, context);
+            }
+            else if (propertyName == nameof(extensions))
+            {
+                extensions = ExtensionsSerialization.Read<MSFT_packing_occlusionRoughnessMetallic>(ref jsonReader, context);
+            }
+            else if (propertyName == nameof(extras))
+            {
+                extras = JsonSerialization.Read(ref jsonReader, context);
+            }
+            else
+            {
+                throw new InvalidDataException($"Unknown property: {propertyName}");
+            }
+        }
+        return new MSFT_packing_occlusionRoughnessMetallic()
+        {
+            OcclusionRoughnessMetallicTexture = occlusionRoughnessMetallicTexture,
+            RoughnessMetallicOcclusionTexture = roughnessMetallicOcclusionTexture,
+            NormalTexture = normalTexture,
+            Extensions = extensions,
+            Extras = extras,
+        };
+    }
+}
+
+public class MsftTextureIndexSerialization
+{
+    public static MsftTextureIndex? Read(ref Utf8JsonReader jsonReader, GltfReaderContext context)
+    {
+        int? index = null;
+        if (jsonReader.TokenType == JsonTokenType.PropertyName && jsonReader.Read())
+        {
+        }
+        if (jsonReader.TokenType == JsonTokenType.Null)
+        {
+            return null;
+        }
+        else if (jsonReader.TokenType != JsonTokenType.StartObject)
+        {
+            throw new InvalidDataException("Failed to find start of property.");
+        }
+        while (jsonReader.Read())
+        {
+            if (jsonReader.TokenType == JsonTokenType.EndObject)
+            {
+                break;
+            }
+            var propertyName = jsonReader.GetString();
+            if (propertyName == nameof(index))
+            {
+                index = ReadInteger(ref jsonReader);
+            }
+            else
+            {
+                throw new InvalidDataException($"Unknown property: {propertyName}");
+            }
+        }
+        return new MsftTextureIndex()
+        {
+            Index = index,
+        };
+    }
+}