stride3d/stride · error · NotImplementedException

Sorting not implemented for multiple vertex buffers by…

Error message

Sorting not implemented for multiple vertex buffers by submeshdata

What it means

SortMeshPolygons only operates on meshes with exactly one vertex buffer; its polygon-sorting code is not implemented for multiple vertex buffers. This NotImplementedException is thrown when meshData.VertexBuffers.Length != 1.

Solutions

1. Re-interleave the mesh into a single vertex buffer before sorting
2. Exclude multi-buffer meshes from polygon sorting
3. Prefer GenerateTangentBinormal-style single-buffer meshes (IsSimple) in the pipeline feeding SortMeshPolygons

Example fix

// before
sort.SortMeshPolygons(multiStreamMesh, viewDir); // 2 vertex buffers
// after
var single = InterleaveVertexBuffers(multiStreamMesh);
sort.SortMeshPolygons(single, viewDir);

if (mesh.VertexBuffers == null || mesh.VertexBuffers.Length != 1)
    mesh = InterleaveToSingleVertexBuffer(mesh);

static bool IsSingleBuffer(MeshDraw mesh) =>
    mesh.VertexBuffers != null && mesh.VertexBuffers.Length == 1;

try { mesh.SortMeshPolygons(viewDir); }
catch (NotImplementedException) { /* re-interleave to one buffer or skip */ }

When it happens

Trigger: Calling SortMeshPolygons on a MeshDraw with 2+ VertexBuffers (e.g. separate position and attribute buffers, or multiple streams).

Common situations: Meshes using multi-stream vertex layouts; meshes from importers that split position data from attribute data; merging workflows that produced multi-buffer meshes.

Related errors

• Non-matching vertex buffer declarations.
• Can only merge TriangleList.
• The mesh Data needs to have index buffer
• meshData is not simple.
• msaaResolverShaderName

AI-assisted analysis of stride3d/stride@96fad776d2 (2026-09-14). Data as JSON: /api/errors/22a804f9e1507e15. Report an issue: GitHub.

Appendix: source

Thrown at sources/engine/Stride.Rendering/Extensions/PolySortExtensions.cs:25

using Stride.Core.Mathematics;
using Stride.Graphics;
using Stride.Graphics.Data;
using Stride.Rendering;

namespace Stride.Extensions
{
    public static class PolySortExtensions
    {
        public static unsafe void SortMeshPolygons(this MeshDraw meshData, Vector3 viewDirectionForSorting)
        {
            // need to have alreade an vertex buffer
            if (meshData.VertexBuffers == null)
                throw new ArgumentException();
            // For now, require a MeshData with an index buffer
            if (meshData.IndexBuffer == null)
                throw new NotImplementedException("The mesh Data needs to have index buffer");
            if (meshData.VertexBuffers.Length != 1)
                throw new NotImplementedException("Sorting not implemented for multiple vertex buffers by submeshdata");

            if (viewDirectionForSorting == Vector3.Zero)
            {
                // By default to -Z if sorting is set to null
                viewDirectionForSorting = -Vector3.UnitZ;
            }

            const uint PolySize = 3; // currently only triangle list are supported
            var polyIndicesSize = PolySize * sizeof(int);
            var vertexBuffer = meshData.VertexBuffers[0];
            var oldIndexBuffer = meshData.IndexBuffer;
            var vertexStride = vertexBuffer.Declaration.VertexStride;

            // Generate the sort list
            var sortList = new List<KeyValuePair<int, Vector3>>();

            fixed (byte* vertexBufferPointerStart = &vertexBuffer.Buffer.GetSerializationData().Content[vertexBuffer.Offset])
            fixed (byte* indexBufferPointerStart = &oldIndexBuffer.Buffer.GetSerializationData().Content[oldIndexBuffer.Offset])

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