stride3d/stride · error · ArgumentException

Cannot specify a semantic index when using the constructor…

Error message

Cannot specify a semantic index when using the constructor with explicit semantic index. Use the implicit semantic index constructor.

What it means

The explicit-index VertexElement constructor (semanticName, semanticIndex, format) requires the semantic name to be index-free; the index is supplied separately. If the name itself matches the semantic-index pattern (e.g. "TEXCOORD0"), the constructor throws to prevent ambiguity.

Solutions

1. Strip the numeric suffix from the name: new VertexElement("TEXCOORD", 0, format)
2. Or keep the name indexed and drop the explicit semanticIndex argument, using the implicit constructor

Example fix

// before
new VertexElement("TEXCOORD0", 1, PixelFormat.R32G32_Float)
// after
new VertexElement("TEXCOORD", 1, PixelFormat.R32G32_Float)

if (Regex.IsMatch(semanticName, @"\d+$") && useExplicitIndex)
    throw new ArgumentException("Strip the numeric suffix before using the explicit-index constructor");

try { new VertexElement(name, index, format); } catch (ArgumentException) { name = Regex.Replace(name, @"\d+$", ""); }

When it happens

Trigger: Calling new VertexElement("TEXCOORD0", 1, PixelFormat...) — i.e. passing an indexed semantic name together with an explicit semanticIndex argument.

Common situations: Mechanical code migration from the string-indexed constructor to the explicit-index constructor without stripping the numeric suffix; copy-paste of semantic names from FX files into the explicit overload.

Related errors

• Could not parse semantic index from the semantic name
• Duplicate s found with the same semantic name and index
• A overlaps with another element. Check the element's offset
• The 's offset and size makes it extend beyond the vertex…
• The offset of the is not a multiple of 4 bytes

AI-assisted analysis of stride3d/stride@96fad776d2 (2026-09-14). Data as JSON: /api/errors/bbc6d68fca0720d1. Report an issue: GitHub.

Appendix: source

Thrown at sources/engine/Stride.Graphics/VertexElement.cs:148

    /// </param>
    /// <exception cref="ArgumentException">
    ///   <paramref name="semanticName"/> is <see langword="null"/> or an empty <see langword="string"/>.
    /// </exception>
    /// <exception cref="ArgumentException">
    ///   Cannot specify a semantic index in the <paramref name="semanticName"/> when using this constructor.
    ///   Use the constructor with explicit semantic index instead (<see cref="VertexElement(string, PixelFormat)"/>).
    /// </exception>
    public VertexElement(string semanticName, int semanticIndex, PixelFormat format, int alignedByteOffset = AppendAligned)
        : this()
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(semanticName);

        // All semantics will be upper case
        semanticName = semanticName.ToUpperInvariant();

        var match = MatchSemanticIndex.Match(semanticName);
        if (match.Success)
            throw new ArgumentException("Cannot specify a semantic index when using the constructor with explicit semantic index. Use the implicit semantic index constructor.");

        // Convert to singleton string in order to speed up things
        // TODO: Stale comment? Use string.Intern?
        this.semanticName = semanticName;
        this.semanticIndex = semanticIndex;
        this.format = format;
        this.alignedByteOffset = alignedByteOffset;

        // Precalculate hashcode
        hashCode = ComputeHashCode();
    }


    /// <summary>
    ///   Gets the HLSL semantic name associated with this element, such as <c>"POSITION"</c>, <c>"TEXCOORD"</c>, or <c>"NORMAL"</c>.
    /// </summary>
    /// <remarks>
    ///   This name must match the semantic used in the Vertex Shader input signature.

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