stride3d/stride · error · ArgumentException

destination length does not match the amount of indices cont

Error message

destination length does not match the amount of indices contained within the index buffer buffer ({destination.Length} / {IndexBufferHelper.Binding.Count})

What it means

The index-buffer reader validates that the destination Span<Vector3> has exactly as many entries as the index buffer's Binding.Count (number of indices, since each index yields one vertex position). When the spans differ, an ArgumentException is thrown because partial or oversized reads are not supported. Note the message text references the vertex-buffer wording due to a shared message template, but the check compares against index count.

Solutions

1. Size the destination span to IndexBufferHelper.Binding.Count before calling Read
2. Recreate the destination array from the actual index buffer count rather than the vertex count
3. If you intended fewer outputs, adjust the index buffer binding Count accordingly
4. Log both destination.Length and Binding.Count to confirm which one is stale

Example fix

// before
var positions = new Vector3[vertexCount];
reader.Read<Color4, Vector3>(ptr, elementCount, stride, positions);
// after
var positions = new Vector3[indexBufferHelper.Binding.Count];
reader.Read<Color4, Vector3>(ptr, elementCount, stride, positions);

if (destination.Length != indexBufferHelper.Binding.Count)
    destination = new Vector3[indexBufferHelper.Binding.Count];

static bool IndexSpanMatches(Vector3[] dest, IndexBufferHelper ib) => dest.Length == ib.Binding.Count;

try { reader.Read<C, V3>(ptr, count, stride, destination); }
catch (ArgumentException ex) { logger.Error(ex, "Index read destination size mismatch"); throw; }

When it happens

Trigger: Calling Read on the index reader with a destination span sized differently from the index buffer's binding count, e.g. allocating the span from the vertex count while the index buffer is larger (indexed geometry), or vice versa.

Common situations: Reading triangle indices for a mesh where indexCount != vertexCount (typical for indexed meshes); reusing a destination buffer from a previous smaller/larger mesh; off-by-one after deduplicating vertices.

Related errors

• destination length does not match the amount of vertices con
• Invalid Z slice index
• MipLevels must be <= {maxMips}
• Width/Height/Depth must be power of 2
• Image format not supported

AI-assisted analysis of stride3d/stride@96fad776d2 (2026-09-14). Data as JSON: /api/errors/2f49c5e68db116c1. Report an issue: GitHub.

Appendix: source

Thrown at sources/engine/Stride.Graphics/VertexBufferHelper.cs:384

        var offset = element.Offset;
        var count = Binding.Count;
            
        fixed (byte* ptrSr = DataInner)
        {
            byte* firstElement = ptrSr + offset;
            reader.Write<TConverter, TSource>(firstElement, count, stride);
        }
    }

    public struct CopyAsTriangleList : IReader<Vector3>
    {
        public required IndexBufferHelper IndexBufferHelper;
        
        public unsafe void Read<TConverter, TSource>(byte* sourcePointer, int elementCount, int stride, Span<Vector3> destination)
            where TConverter : IConverter<TSource, Vector3> where TSource : unmanaged
        {
            if (destination.Length != IndexBufferHelper.Binding.Count)
                throw new ArgumentException($"{nameof(destination)} length does not match the amount of indices contained within the index buffer buffer ({destination.Length} / {IndexBufferHelper.Binding.Count})");

            fixed (Vector3* destPtr = destination)
            {
                Vector3* dest = destPtr;
                if (IndexBufferHelper.Is32Bit(out var indices32, out var indices16))
                {
                    foreach (var index in indices32)
                    {
                        TConverter.Convert(*(TSource*)(sourcePointer + index * stride), out *dest);
                        dest++;
                    }
                }
                else
                {
                    foreach (var index in indices16)
                    {
                        TConverter.Convert(*(TSource*)(sourcePointer + index * stride), out *dest);
                        dest++;

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