Merge pull request #21 from B3zaleel/implement-KHR_materials_iridesce…

…nce-extension

Implement KHR_materials_iridescence Gltf extension

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

@@ -0,0 +1,149 @@
+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 an iridescence effect.
+/// </summary>
+public class KHR_materials_iridescence : IGltfProperty
+{
+    /// <summary>
+    /// The iridescence intensity factor.
+    /// </summary>
+    public float IridescenceFactor { get; set; }
+    /// <summary>
+    /// The iridescence intensity texture. The values are sampled from the R channel. These values are linear.
+    /// </summary>
+    public TextureInfo? IridescenceTexture { get; set; }
+    /// <summary>
+    /// The index of refraction of the dielectric thin-film layer.
+    /// </summary>
+    public float IridescenceIor { get; set; }
+    /// <summary>
+    /// The minimum thickness of the thin-film layer given in nanometers.
+    /// </summary>
+    public float IridescenceThicknessMinimum { get; set; }
+    /// <summary>
+    /// The maximum thickness of the thin-film layer given in nanometers.
+    /// </summary>
+    public float IridescenceThicknessMaximum { get; set; }
+    /// <summary>
+    /// The thickness texture of the thin-film layer to linearly interpolate between the minimum and 
+    /// maximum thickness given by the corresponding properties, where a sampled value of `0.0` represents 
+    /// the minimum thickness and a sampled value of `1.0` represents the maximum thickness.
+    /// </summary>
+    public TextureInfo? IridescenceThicknessTexture { get; set; }
+    public Dictionary<string, object?>? Extensions { get; set; }
+    public object? Extras { get; set; }
+}
+
+public class KhrMaterialsIridescenceExtension : IGltfExtension
+{
+    public string Name => nameof(KHR_materials_iridescence);
+    public const float Default_IridescenceFactor = 0.0f;
+    public const float Default_IridescenceIor = 1.3f;
+    public const float Default_IridescenceThicknessMinimum = 100.0f;
+    public const float Default_IridescenceThicknessMaximum = 400.0f;
+
+    public object? Read(ref Utf8JsonReader jsonReader, GltfReaderContext context, Type parentType)
+    {
+        if (parentType != typeof(Material))
+        {
+            throw new InvalidDataException("KHR_materials_iridescence must be used in a Material.");
+        }
+        float? iridescenceFactor = null;
+        TextureInfo? iridescenceTexture = null;
+        float? iridescenceIor = null;
+        float? iridescenceThicknessMinimum = null;
+        float? iridescenceThicknessMaximum = null;
+        TextureInfo? iridescenceThicknessTexture = 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(iridescenceFactor))
+            {
+                iridescenceFactor = ReadFloat(ref jsonReader);
+            }
+            else if (propertyName == nameof(iridescenceTexture))
+            {
+                iridescenceTexture = TextureInfoSerialization.Read(ref jsonReader, context);
+            }
+            else if (propertyName == nameof(iridescenceIor))
+            {
+                iridescenceIor = ReadFloat(ref jsonReader);
+            }
+            else if (propertyName == nameof(iridescenceThicknessMinimum))
+            {
+                iridescenceThicknessMinimum = ReadFloat(ref jsonReader);
+            }
+            else if (propertyName == nameof(iridescenceThicknessMaximum))
+            {
+                iridescenceThicknessMaximum = ReadFloat(ref jsonReader);
+            }
+            else if (propertyName == nameof(iridescenceThicknessTexture))
+            {
+                iridescenceThicknessTexture = TextureInfoSerialization.Read(ref jsonReader, context);
+            }
+            else if (propertyName == nameof(extensions))
+            {
+                extensions = ExtensionsSerialization.Read<KHR_materials_iridescence>(ref jsonReader, context);
+            }
+            else if (propertyName == nameof(extras))
+            {
+                extras = JsonSerialization.Read(ref jsonReader, context);
+            }
+            else
+            {
+                throw new InvalidDataException($"Unknown property: {propertyName}");
+            }
+        }
+        if (iridescenceFactor != null && (iridescenceFactor < 0.0f || iridescenceFactor > 1.0f))
+        {
+            throw new InvalidDataException("KHR_materials_iridescence.iridescenceFactor must be in the range [0.0, 1.0].");
+        }
+        if (iridescenceIor != null && iridescenceIor < 1.0f)
+        {
+            throw new InvalidDataException("KHR_materials_iridescence.iridescenceIor must be greater than or equal to 1.0.");
+        }
+        if (iridescenceThicknessMinimum != null && iridescenceThicknessMinimum < 0.0f)
+        {
+            throw new InvalidDataException("KHR_materials_iridescence.iridescenceThicknessMinimum must be greater than or equal to 0.0.");
+        }
+        if (iridescenceThicknessMaximum != null && iridescenceThicknessMaximum < 0.0f)
+        {
+            throw new InvalidDataException("KHR_materials_iridescence.iridescenceThicknessMaximum must be greater than or equal to 0.0.");
+        }
+
+        return new KHR_materials_iridescence()
+        {
+            IridescenceFactor = iridescenceFactor ?? Default_IridescenceFactor,
+            IridescenceTexture = iridescenceTexture,
+            IridescenceIor = iridescenceIor ?? Default_IridescenceIor,
+            IridescenceThicknessMinimum = iridescenceThicknessMinimum ?? Default_IridescenceThicknessMinimum,
+            IridescenceThicknessMaximum = iridescenceThicknessMaximum ?? Default_IridescenceThicknessMaximum,
+            IridescenceThicknessTexture = iridescenceThicknessTexture,
+            Extensions = extensions,
+            Extras = extras,
+        };
+    }
+}