Fix MeshAccessor.Stream count for items not aligned to buffer start

Source/Engine/Graphics/Models/MeshAccessor.cs

@@ -18,13 +18,14 @@ namespace FlaxEngine
         {
             private Span<byte> _data;
             private PixelFormat _format;
-            private int _stride;
+            private int _stride, _count;
             private readonly PixelFormatSampler _sampler;
 
-            internal Stream(Span<byte> data, PixelFormat format, int stride)
+            internal Stream(Span<byte> data, PixelFormat format, int stride, int count)
             {
                 _data = data;
                 _stride = stride;
+                _count = count;
                 if (PixelFormatSampler.Get(format, out _sampler))
                 {
                     _format = format;
@@ -53,7 +54,7 @@ namespace FlaxEngine
             /// <summary>
             /// Gets the count of the items in the stride.
             /// </summary>
-            public int Count => _data.Length / _stride;
+            public int Count => _count;
 
             /// <summary>
             /// Returns true if stream is valid.
@@ -664,15 +665,16 @@ namespace FlaxEngine
         {
             Span<byte> data = new Span<byte>();
             PixelFormat format = PixelFormat.Unknown;
-            int stride = 0;
+            int stride = 0, count = 0;
             var ib = _data[(int)MeshBufferType.Index];
             if (ib != null)
             {
                 data = ib;
                 format = _formats[(int)MeshBufferType.Index];
                 stride = PixelFormatExtensions.SizeInBytes(format);
+                count = data.Length / stride;
             }
-            return new Stream(data, format, stride);
+            return new Stream(data, format, stride, count);
         }
 
         /// <summary>
@@ -684,7 +686,7 @@ namespace FlaxEngine
         {
             Span<byte> data = new Span<byte>();
             PixelFormat format = PixelFormat.Unknown;
-            int stride = 0;
+            int stride = 0, count = 0;
             for (int vbIndex = 0; vbIndex < 3 && format == PixelFormat.Unknown; vbIndex++)
             {
                 int idx = vbIndex + 1;
@@ -699,11 +701,12 @@ namespace FlaxEngine
                         data = new Span<byte>(vb).Slice(e.Offset);
                         format = e.Format;
                         stride = (int)layout.Stride;
+                        count = vb.Length / stride;
                         break;
                     }
                 }
             }
-            return new Stream(data, format, stride);
+            return new Stream(data, format, stride, count);
         }
 
         /// <summary>

Source/Engine/Graphics/Models/MeshAccessor.h

@@ -25,10 +25,10 @@ public:
     private:
         Span<byte> _data;
         PixelFormat _format;
-        int32 _stride;
+        int32 _stride, _count;
         PixelFormatSampler _sampler;
 
-        Stream(Span<byte> data, PixelFormat format, int32 stride);
+        Stream(Span<byte> data, PixelFormat format, int32 stride, int32 count);
 
     public:
         Span<byte> GetData() const;

Source/Engine/Graphics/Models/MeshBase.cpp

@@ -38,10 +38,11 @@ namespace
 #endif
 }
 
-MeshAccessor::Stream::Stream(Span<byte> data, PixelFormat format, int32 stride)
+MeshAccessor::Stream::Stream(Span<byte> data, PixelFormat format, int32 stride, int32 count)
     : _data(data)
     , _format(PixelFormat::Unknown)
     , _stride(stride)
+    , _count(count)
 {
     auto sampler = PixelFormatSampler::Get(format);
     if (sampler)
@@ -72,7 +73,7 @@ int32 MeshAccessor::Stream::GetStride() const
 
 int32 MeshAccessor::Stream::GetCount() const
 {
-    return _data.Length() / _stride;
+    return _count;
 }
 
 bool MeshAccessor::Stream::IsValid() const
@@ -368,22 +369,23 @@ MeshAccessor::Stream MeshAccessor::Index()
 {
     Span<byte> data;
     PixelFormat format = PixelFormat::Unknown;
-    int32 stride = 0;
+    int32 stride = 0, count = 0;
     auto& ib = _data[(int32)MeshBufferType::Index];
     if (ib.IsValid())
     {
         data = ib;
         format = _formats[(int32)MeshBufferType::Index];
         stride = PixelFormatExtensions::SizeInBytes(format);
+        count = data.Length() / stride;
     }
-    return Stream(data, format, stride);
+    return Stream(data, format, stride, count);
 }
 
 MeshAccessor::Stream MeshAccessor::Attribute(VertexElement::Types attribute)
 {
     Span<byte> data;
     PixelFormat format = PixelFormat::Unknown;
-    int32 stride = 0;
+    int32 stride = 0, count = 0;
     for (int32 vbIndex = 0; vbIndex < 3 && format == PixelFormat::Unknown; vbIndex++)
     {
         static_assert((int32)MeshBufferType::Vertex0 == 1, "Update code.");
@@ -399,11 +401,12 @@ MeshAccessor::Stream MeshAccessor::Attribute(VertexElement::Types attribute)
                 data = vb.Slice(e.Offset);
                 format = e.Format;
                 stride = layout->GetStride();
+                count = vb.Length() / stride;
                 break;
             }
         }
     }
-    return Stream(data, format, stride);
+    return Stream(data, format, stride, count);
 }
 
 MeshBase::~MeshBase()