Merge pull request #15 from B3zaleel/implement-KHR_materials_clearcoa…

…t-extension

Implement KHR_materials_clearcoat Gltf extension

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

@@ -0,0 +1,126 @@
+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 the clearcoat material layer.
+/// </summary>
+public class KHR_materials_clearcoat : IGltfProperty
+{
+    /// <summary>
+    /// The clearcoat layer intensity (aka opacity) of the material.
+    /// </summary>
+    public float ClearcoatFactor { get; set; }
+    /// <summary>
+    /// The clearcoat layer intensity texture. These values are sampled from the R channel.
+    /// </summary>
+    public TextureInfo? ClearcoatTexture { get; set; }
+    /// <summary>
+    /// The clearcoat layer roughness of the material.
+    /// </summary>
+    public float ClearcoatRoughnessFactor { get; set; }
+    /// <summary>
+    /// The clearcoat layer roughness texture. These values are sampled from the G channel.
+    /// </summary>
+    public TextureInfo? ClearcoatRoughnessTexture { get; set; }
+    /// <summary>
+    /// A tangent space normal map for the clearcoat layer.
+    /// </summary>
+    public MaterialNormalTextureInfo? ClearcoatNormalTexture { get; set; }
+    public Dictionary<string, object?>? Extensions { get; set; }
+    public object? Extras { get; set; }
+}
+
+public class KhrMaterialsClearcoatExtension : IGltfExtension
+{
+    public string Name => nameof(KHR_materials_clearcoat);
+    public const float Default_ClearcoatFactor = 0.0f;
+    public const float Default_ClearcoatRoughnessFactor = 0.0f;
+
+    public object? Read(ref Utf8JsonReader jsonReader, GltfReaderContext context, Type parentType)
+    {
+        if (parentType != typeof(Material))
+        {
+            throw new InvalidDataException("KHR_materials_clearcoat must be used in a Material.");
+        }
+        float? clearcoatFactor = null;
+        TextureInfo? clearcoatTexture = null;
+        float? clearcoatRoughnessFactor = null;
+        TextureInfo? clearcoatRoughnessTexture = null;
+        MaterialNormalTextureInfo? clearcoatNormalTexture = 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(clearcoatFactor))
+            {
+                clearcoatFactor = ReadFloat(ref jsonReader);
+            }
+            else if (propertyName == nameof(clearcoatTexture))
+            {
+                clearcoatTexture = TextureInfoSerialization.Read(ref jsonReader, context);
+            }
+            else if (propertyName == nameof(clearcoatRoughnessFactor))
+            {
+                clearcoatRoughnessFactor = ReadFloat(ref jsonReader);
+            }
+            else if (propertyName == nameof(clearcoatRoughnessTexture))
+            {
+                clearcoatRoughnessTexture = TextureInfoSerialization.Read(ref jsonReader, context);
+            }
+            else if (propertyName == nameof(clearcoatNormalTexture))
+            {
+                clearcoatNormalTexture = MaterialNormalTextureInfoSerialization.Read(ref jsonReader, context);
+            }
+            else if (propertyName == nameof(extensions))
+            {
+                extensions = ExtensionsSerialization.Read<KHR_materials_clearcoat>(ref jsonReader, context);
+            }
+            else if (propertyName == nameof(extras))
+            {
+                extras = JsonSerialization.Read(ref jsonReader, context);
+            }
+            else
+            {
+                throw new InvalidDataException($"Unknown property: {propertyName}");
+            }
+        }
+        if (clearcoatFactor != null && (clearcoatFactor < 0.0f || clearcoatFactor > 1.0f))
+        {
+            throw new InvalidDataException("KHR_materials_clearcoat.clearcoatFactor must be in the range [0.0, 1.0].");
+        }
+        if (clearcoatRoughnessFactor != null && (clearcoatRoughnessFactor < 0.0f || clearcoatRoughnessFactor > 1.0f))
+        {
+            throw new InvalidDataException("KHR_materials_clearcoat.clearcoatRoughnessFactor must be in the range [0.0, 1.0].");
+        }
+        return new KHR_materials_clearcoat()
+        {
+            ClearcoatFactor = clearcoatFactor ?? Default_ClearcoatFactor,
+            ClearcoatTexture = clearcoatTexture,
+            ClearcoatRoughnessFactor = clearcoatRoughnessFactor ?? Default_ClearcoatRoughnessFactor,
+            ClearcoatRoughnessTexture = clearcoatRoughnessTexture,
+            ClearcoatNormalTexture = clearcoatNormalTexture,
+            Extensions = extensions,
+            Extras = extras,
+        };
+    }
+}