Fixed Skinning issue when using 8 Weights;

src/SharpGLTF.Core/Memory/MemoryAccessor.Validation.cs

@@ -182,12 +182,17 @@ namespace SharpGLTF.Memory
                 return;
             }
 
+            // check for WEIGHTS_0 + WEIGHTS_1
+
             if (weights0 == null) throw new ArgumentNullException(nameof(weights0));
 
+            if (weights0.Attribute.Encoding != weights1.Attribute.Encoding) throw new ArgumentException("WEIGHTS_0 and WEIGHTS_1 format mismatch.", nameof(weights1.Attribute));
+
             var len = weights0.Attribute.ItemByteLength;
             Span<Byte> dst = stackalloc byte[len * 2];
 
-            var zip = weights0.GetItemsAsRawBytes().Zip(weights1.GetItemsAsRawBytes(), (a, b) => (a, b));
+            var zip = weights0.GetItemsAsRawBytes()
+                 .Zip(weights1.GetItemsAsRawBytes(), (a, b) => (a, b));
 
             foreach (var (a, b) in zip)
             {
@@ -203,11 +208,11 @@ namespace SharpGLTF.Memory
             }
         }
 
-        private static bool _CheckWeightSum(Span<byte> dst, ENCODING encoding)
+        private static bool _CheckWeightSum(ReadOnlySpan<byte> src, ENCODING encoding)
         {
             if (encoding == ENCODING.UNSIGNED_BYTE)
             {
-                var weights = dst;
+                var weights = src;
 
                 int r = 0;
                 for (int j = 0; j < weights.Length; ++j) r += weights[j];
@@ -216,7 +221,7 @@ namespace SharpGLTF.Memory
 
             if (encoding == ENCODING.UNSIGNED_SHORT)
             {
-                var weights = System.Runtime.InteropServices.MemoryMarshal.Cast<Byte, UInt16>(dst);
+                var weights = System.Runtime.InteropServices.MemoryMarshal.Cast<Byte, UInt16>(src);
 
                 int r = 0;
                 for (int j = 0; j < weights.Length; ++j) r += weights[j];
@@ -225,7 +230,7 @@ namespace SharpGLTF.Memory
 
             if (encoding == ENCODING.FLOAT)
             {
-                var weights = System.Runtime.InteropServices.MemoryMarshal.Cast<Byte, Single>(dst);
+                var weights = System.Runtime.InteropServices.MemoryMarshal.Cast<Byte, Single>(src);
 
                 float nonZero = 0;
                 float sum = 0;

src/SharpGLTF.Core/Schema2/gltf.Accessors.cs

@@ -381,7 +381,7 @@ namespace SharpGLTF.Schema2
             if (attributes.TryGetValue("TANGENT", out Accessor tangents)) tangents._ValidateTangents(validate);
 
             if (attributes.TryGetValue("JOINTS_0", out Accessor joints0)) joints0._ValidateJoints(validate, "JOINTS_0", skinsMaxJointCount);
-            if (attributes.TryGetValue("JOINTS_1", out Accessor joints1)) joints0._ValidateJoints(validate, "JOINTS_1", skinsMaxJointCount);
+            if (attributes.TryGetValue("JOINTS_1", out Accessor joints1)) joints1._ValidateJoints(validate, "JOINTS_1", skinsMaxJointCount);
 
             attributes.TryGetValue("WEIGHTS_0", out Accessor weights0);
             attributes.TryGetValue("WEIGHTS_1", out Accessor weights1);

src/SharpGLTF.Toolkit/Geometry/VertexTypes/VertexSkinning.cs

@@ -230,7 +230,7 @@ namespace SharpGLTF.Geometry.VertexTypes
         [System.Diagnostics.DebuggerBrowsable(System.Diagnostics.DebuggerBrowsableState.Never)]
         Vector4 IVertexSkinning.WeightsLow => this.Weights0;
         [System.Diagnostics.DebuggerBrowsable(System.Diagnostics.DebuggerBrowsableState.Never)]
-        Vector4 IVertexSkinning.WeightsHigh => this.Joints1;
+        Vector4 IVertexSkinning.WeightsHigh => this.Weights1;
 
         #endregion
 

tests/SharpGLTF.Toolkit.Tests/Scenes/SceneBuilderTests.cs

@@ -15,7 +15,8 @@ namespace SharpGLTF.Scenes
 {
     using VPOSNRM = VertexBuilder<VertexPositionNormal, VertexEmpty, VertexEmpty>;
 
-    using SKINNEDVERTEX = VertexBuilder<VertexPosition, VertexEmpty, VertexJoints4>;
+    using SKINNEDVERTEX4 = VertexBuilder<VertexPosition, VertexEmpty, VertexJoints4>;
+    using SKINNEDVERTEX8 = VertexBuilder<VertexPosition, VertexEmpty, VertexJoints8>;
 
 
     [Category("Toolkit.Scenes")]
@@ -230,22 +231,22 @@ namespace SharpGLTF.Scenes
             const int jointIdx1 = 1; // index of joint node 1
             const int jointIdx2 = 2; // index of joint node 2
 
-            var v1 = new SKINNEDVERTEX(new Vector3(-10, 0, +10), (jointIdx0, 1));
-            var v2 = new SKINNEDVERTEX(new Vector3(+10, 0, +10), (jointIdx0, 1));
-            var v3 = new SKINNEDVERTEX(new Vector3(+10, 0, -10), (jointIdx0, 1));
-            var v4 = new SKINNEDVERTEX(new Vector3(-10, 0, -10), (jointIdx0, 1));
+            var v1 = new SKINNEDVERTEX4(new Vector3(-10, 0, +10), (jointIdx0, 1));
+            var v2 = new SKINNEDVERTEX4(new Vector3(+10, 0, +10), (jointIdx0, 1));
+            var v3 = new SKINNEDVERTEX4(new Vector3(+10, 0, -10), (jointIdx0, 1));
+            var v4 = new SKINNEDVERTEX4(new Vector3(-10, 0, -10), (jointIdx0, 1));
 
-            var v5 = new SKINNEDVERTEX(new Vector3(-10, 40, +10), (jointIdx0, 0.5f), (jointIdx1, 0.5f));
-            var v6 = new SKINNEDVERTEX(new Vector3(+10, 40, +10), (jointIdx0, 0.5f), (jointIdx1, 0.5f));
-            var v7 = new SKINNEDVERTEX(new Vector3(+10, 40, -10), (jointIdx0, 0.5f), (jointIdx1, 0.5f));
-            var v8 = new SKINNEDVERTEX(new Vector3(-10, 40, -10), (jointIdx0, 0.5f), (jointIdx1, 0.5f));
+            var v5 = new SKINNEDVERTEX4(new Vector3(-10, 40, +10), (jointIdx0, 0.5f), (jointIdx1, 0.5f));
+            var v6 = new SKINNEDVERTEX4(new Vector3(+10, 40, +10), (jointIdx0, 0.5f), (jointIdx1, 0.5f));
+            var v7 = new SKINNEDVERTEX4(new Vector3(+10, 40, -10), (jointIdx0, 0.5f), (jointIdx1, 0.5f));
+            var v8 = new SKINNEDVERTEX4(new Vector3(-10, 40, -10), (jointIdx0, 0.5f), (jointIdx1, 0.5f));
 
-            var v9  = new SKINNEDVERTEX(new Vector3(-5, 80, +5), (jointIdx2, 1));
-            var v10 = new SKINNEDVERTEX(new Vector3(+5, 80, +5), (jointIdx2, 1));
-            var v11 = new SKINNEDVERTEX(new Vector3(+5, 80, -5), (jointIdx2, 1));
-            var v12 = new SKINNEDVERTEX(new Vector3(-5, 80, -5), (jointIdx2, 1));
+            var v9  = new SKINNEDVERTEX4(new Vector3(-5, 80, +5), (jointIdx2, 1));
+            var v10 = new SKINNEDVERTEX4(new Vector3(+5, 80, +5), (jointIdx2, 1));
+            var v11 = new SKINNEDVERTEX4(new Vector3(+5, 80, -5), (jointIdx2, 1));
+            var v12 = new SKINNEDVERTEX4(new Vector3(-5, 80, -5), (jointIdx2, 1));
 
-            var mesh = SKINNEDVERTEX.CreateCompatibleMesh("mesh1");
+            var mesh = SKINNEDVERTEX4.CreateCompatibleMesh("mesh1");
 
             #if DEBUG
             mesh.VertexPreprocessor.SetValidationPreprocessors();
@@ -317,22 +318,22 @@ namespace SharpGLTF.Scenes
             const int jointIdx1 = 1; // index of joint node 1
             const int jointIdx2 = 2; // index of joint node 2
 
-            var v1 = new SKINNEDVERTEX(new Vector3(-10, 0, +10), (jointIdx0, 1));
-            var v2 = new SKINNEDVERTEX(new Vector3(+10, 0, +10), (jointIdx0, 1));
-            var v3 = new SKINNEDVERTEX(new Vector3(+10, 0, -10), (jointIdx0, 1));
-            var v4 = new SKINNEDVERTEX(new Vector3(-10, 0, -10), (jointIdx0, 1));
+            var v1 = new SKINNEDVERTEX4(new Vector3(-10, 0, +10), (jointIdx0, 1));
+            var v2 = new SKINNEDVERTEX4(new Vector3(+10, 0, +10), (jointIdx0, 1));
+            var v3 = new SKINNEDVERTEX4(new Vector3(+10, 0, -10), (jointIdx0, 1));
+            var v4 = new SKINNEDVERTEX4(new Vector3(-10, 0, -10), (jointIdx0, 1));
 
-            var v5 = new SKINNEDVERTEX(new Vector3(-10, 40, +10), (jointIdx0, 0.5f), (jointIdx1, 0.5f));
-            var v6 = new SKINNEDVERTEX(new Vector3(+10, 40, +10), (jointIdx0, 0.5f), (jointIdx1, 0.5f));
-            var v7 = new SKINNEDVERTEX(new Vector3(+10, 40, -10), (jointIdx0, 0.5f), (jointIdx1, 0.5f));
-            var v8 = new SKINNEDVERTEX(new Vector3(-10, 40, -10), (jointIdx0, 0.5f), (jointIdx1, 0.5f));
+            var v5 = new SKINNEDVERTEX4(new Vector3(-10, 40, +10), (jointIdx0, 0.5f), (jointIdx1, 0.5f));
+            var v6 = new SKINNEDVERTEX4(new Vector3(+10, 40, +10), (jointIdx0, 0.5f), (jointIdx1, 0.5f));
+            var v7 = new SKINNEDVERTEX4(new Vector3(+10, 40, -10), (jointIdx0, 0.5f), (jointIdx1, 0.5f));
+            var v8 = new SKINNEDVERTEX4(new Vector3(-10, 40, -10), (jointIdx0, 0.5f), (jointIdx1, 0.5f));
 
-            var v9 = new SKINNEDVERTEX(new Vector3(-5, 80, +5), (jointIdx2, 1));
-            var v10 = new SKINNEDVERTEX(new Vector3(+5, 80, +5), (jointIdx2, 1));
-            var v11 = new SKINNEDVERTEX(new Vector3(+5, 80, -5), (jointIdx2, 1));
-            var v12 = new SKINNEDVERTEX(new Vector3(-5, 80, -5), (jointIdx2, 1));
+            var v9 = new SKINNEDVERTEX4(new Vector3(-5, 80, +5), (jointIdx2, 1));
+            var v10 = new SKINNEDVERTEX4(new Vector3(+5, 80, +5), (jointIdx2, 1));
+            var v11 = new SKINNEDVERTEX4(new Vector3(+5, 80, -5), (jointIdx2, 1));
+            var v12 = new SKINNEDVERTEX4(new Vector3(-5, 80, -5), (jointIdx2, 1));
 
-            var mesh = SKINNEDVERTEX.CreateCompatibleMesh("mesh1");
+            var mesh = SKINNEDVERTEX4.CreateCompatibleMesh("mesh1");
 
             #if DEBUG
             mesh.VertexPreprocessor.SetValidationPreprocessors();
@@ -706,5 +707,54 @@ namespace SharpGLTF.Scenes
             scene.AttachToCurrentTest("construction.glb");
         }
 
+        [Test(Description = "Creates a scene using 8 weight skins")]
+        public void CreateSkinnedSceneWith8Weights()
+        {
+            // create plane mesh
+
+            (int, float)[] binds = new[]
+            {
+                (0, 0.125f),
+                (1, 0.125f),
+                (2, 0.125f),
+                (3, 0.125f),
+                (4, 0.125f),
+                (5, 0.125f),
+                (6, 0.125f),
+                (7, 0.125f),
+            };
+
+            var v0 = new SKINNEDVERTEX8(new Vector3(1, 0, 1), binds);
+            var v1 = new SKINNEDVERTEX8(new Vector3(-1, 0, 1), binds);
+            var v2 = new SKINNEDVERTEX8(new Vector3(-1, 0, -1), binds);
+            var v3 = new SKINNEDVERTEX8(new Vector3(1, 0, -1), binds);
+
+            var mesh = SKINNEDVERTEX8.CreateCompatibleMesh();
+            var prim = mesh.UsePrimitive(MaterialBuilder.CreateDefault());
+
+            prim.AddTriangle(v0, v1, v2);
+            prim.AddTriangle(v0, v2, v3);
+
+            // create armature
+
+            var root = new NodeBuilder();
+            var n0 = root.CreateNode();
+            var n1 = n0.CreateNode();
+            var n2 = n1.CreateNode();
+            var n3 = n2.CreateNode();
+            var n4 = n3.CreateNode();
+            var n5 = n4.CreateNode();
+            var n6 = n5.CreateNode();
+            var n7 = n6.CreateNode();
+
+            // create scene
+
+            var scene = new SceneBuilder();
+
+            scene.AddSkinnedMesh(mesh, Matrix4x4.Identity, n0, n1, n2, n3, n4, n5, n6, n7);
+
+            scene.AttachToCurrentTest("output.gltf");
+        }
+
     }
 }