Merge pull request #14 from B3zaleel/implement-KHR_materials_anisotro…

…py-extension

Implement KHR_materials_anisotropy Gltf extension

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

@@ -0,0 +1,98 @@
+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 defines anisotropy.
+/// </summary>
+public class KHR_materials_anisotropy : IGltfProperty
+{
+    /// <summary>
+    /// The anisotropy strength. When anisotropyTexture is present, this value is multiplied by the blue channel.
+    /// </summary>
+    public float AnisotropyStrength { get; set; }
+    /// <summary>
+    /// The rotation of the anisotropy in tangent, bitangent space, measured in radians counter-clockwise from the tangent.
+    /// </summary>
+    public float AnisotropyRotation { get; set; }
+    /// <summary>
+    /// The anisotropy texture. Red and green channels represent the anisotropy direction in [-1, 1] tangent, bitangent space, to be rotated by anisotropyRotation.
+    /// </summary>
+    public TextureInfo? AnisotropyTexture { get; set; }
+    public Dictionary<string, object?>? Extensions { get; set; }
+    public object? Extras { get; set; }
+}
+
+public class KhrMaterialsAnisotropyExtension : IGltfExtension
+{
+    public string Name => nameof(KHR_materials_anisotropy);
+    public const float Default_AnisotropyStrength = 0.0f;
+    public const float Default_AnisotropyRotation = 0.0f;
+
+    public object? Read(ref Utf8JsonReader jsonReader, GltfReaderContext context, Type parentType)
+    {
+        if (parentType != typeof(Material))
+        {
+            throw new InvalidDataException("KHR_materials_anisotropy must be used in a Material.");
+        }
+        float? anisotropyStrength = null;
+        float? anisotropyRotation = null;
+        TextureInfo? anisotropyTexture = 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(anisotropyStrength))
+            {
+                anisotropyStrength = ReadFloat(ref jsonReader);
+            }
+            else if (propertyName == nameof(anisotropyRotation))
+            {
+                anisotropyRotation = ReadFloat(ref jsonReader);
+            }
+            else if (propertyName == nameof(anisotropyTexture))
+            {
+                anisotropyTexture = TextureInfoSerialization.Read(ref jsonReader, context);
+            }
+            else if (propertyName == nameof(extensions))
+            {
+                extensions = ExtensionsSerialization.Read<KHR_materials_anisotropy>(ref jsonReader, context);
+            }
+            else if (propertyName == nameof(extras))
+            {
+                extras = JsonSerialization.Read(ref jsonReader, context);
+            }
+            else
+            {
+                throw new InvalidDataException($"Unknown property: {propertyName}");
+            }
+        }
+        return new KHR_materials_anisotropy()
+        {
+            AnisotropyStrength = anisotropyStrength ?? Default_AnisotropyStrength,
+            AnisotropyRotation = anisotropyRotation ?? Default_AnisotropyRotation,
+            AnisotropyTexture = anisotropyTexture,
+            Extensions = extensions,
+            Extras = extras,
+        };
+    }
+}