Increased mesh decoders support from 1 color set to 2, and 2 UVs to 4 UVs

src/SharpGLTF.Core/Runtime/MeshDecoder.Schema2.cs

@@ -147,8 +147,12 @@ namespace SharpGLTF.Runtime
             // additional vertex attributes (color + UVs + Skinning)
 
             _Color0 = srcPrim.GetVertexAccessor("COLOR_0")?.AsColorArray() as IReadOnlyList<XYZW>;
+            _Color1 = srcPrim.GetVertexAccessor("COLOR_1")?.AsColorArray() as IReadOnlyList<XYZW>;
+
             _TexCoord0 = srcPrim.GetVertexAccessor("TEXCOORD_0")?.AsVector2Array() as IReadOnlyList<XY>;
             _TexCoord1 = srcPrim.GetVertexAccessor("TEXCOORD_1")?.AsVector2Array() as IReadOnlyList<XY>;
+            _TexCoord2 = srcPrim.GetVertexAccessor("TEXCOORD_2")?.AsVector2Array() as IReadOnlyList<XY>;
+            _TexCoord3 = srcPrim.GetVertexAccessor("TEXCOORD_3")?.AsVector2Array() as IReadOnlyList<XY>;
 
             _Joints0 = srcPrim.GetVertexAccessor("JOINTS_0")?.AsVector4Array() as IReadOnlyList<XYZW>;
             _Joints1 = srcPrim.GetVertexAccessor("JOINTS_1")?.AsVector4Array() as IReadOnlyList<XYZW>;
@@ -184,9 +188,12 @@ namespace SharpGLTF.Runtime
         internal readonly List<_MorphTargetDecoder> _MorphTargets = new List<_MorphTargetDecoder>();
 
         private readonly IReadOnlyList<XYZW> _Color0;
+        private readonly IReadOnlyList<XYZW> _Color1;
 
         private readonly IReadOnlyList<XY> _TexCoord0;
         private readonly IReadOnlyList<XY> _TexCoord1;
+        private readonly IReadOnlyList<XY> _TexCoord2;
+        private readonly IReadOnlyList<XY> _TexCoord3;
 
         private readonly IReadOnlyList<XYZW> _Joints0;
         private readonly IReadOnlyList<XYZW> _Joints1;
@@ -202,9 +209,12 @@ namespace SharpGLTF.Runtime
 
         public int VertexCount => _Geometry.VertexCount;
 
-        public int ColorsCount => _Color0 != null ? 1 : 0;
+        public int ColorsCount => (_Color0 != null ? 1 : 0) + (_Color1 != null ? 1 : 0);
 
-        public int TexCoordsCount => (_TexCoord0 != null ? 1 : 0) + (_TexCoord1 != null ? 1 : 0);
+        public int TexCoordsCount => (_TexCoord0 != null ? 1 : 0)
+            + (_TexCoord1 != null ? 1 : 0)
+            + (_TexCoord2 != null ? 1 : 0)
+            + (_TexCoord3 != null ? 1 : 0);
 
         public int JointsWeightsCount => (_Joints0 != null ? 4 : 0) + (_Joints1 != null ? 4 : 0);
 
@@ -267,6 +277,8 @@ namespace SharpGLTF.Runtime
         {
             if (set == 0 && _TexCoord0 != null) return _TexCoord0[vertexIndex];
             if (set == 1 && _TexCoord1 != null) return _TexCoord1[vertexIndex];
+            if (set == 2 && _TexCoord2 != null) return _TexCoord2[vertexIndex];
+            if (set == 3 && _TexCoord3 != null) return _TexCoord3[vertexIndex];
 
             return XY.Zero;
         }
@@ -274,6 +286,7 @@ namespace SharpGLTF.Runtime
         public XYZW GetColor(int vertexIndex, int set)
         {
             if (set == 0 && _Color0 != null) return _Color0[vertexIndex];
+            if (set == 1 && _Color1 != null) return _Color1[vertexIndex];
 
             return XYZW.One;
         }