egametang/ET · error · Exception

Invalid number of face vertices: 3 coordinates expected, fou

Error message

Invalid number of face vertices: 3 coordinates expected, found {v.Length}

What it means

Thrown by ObjImporter.ReadFace when a face ('f') line, after splitting, has fewer than 4 tokens — i.e., fewer than 3 vertex references. A valid polygonal face needs at least 3 vertices; the OBJ line is incomplete.

Source

Thrown at Packages/cn.etetet.recast/Scripts/Core/Share/Recast/ObjImporter.cs:103

            {
                throw new Exception("Invalid vector, expected 3 coordinates, found " + (v.Length - 1));
            }

            // fix - https://github.com/ikpil/DotRecast/issues/7
            return new float[]
            {
                float.Parse(v[1], CultureInfo.InvariantCulture), 
                float.Parse(v[2], CultureInfo.InvariantCulture), 
                float.Parse(v[3], CultureInfo.InvariantCulture)
            };
        }

        private static void ReadFace(string line, ObjImporterContext context)
        {
            string[] v = line.Split(' ', StringSplitOptions.RemoveEmptyEntries);
            if (v.Length < 4)
            {
                throw new Exception("Invalid number of face vertices: 3 coordinates expected, found " + v.Length);
            }

            for (int j = 0; j < v.Length - 3; j++)
            {
                context.meshFaces.Add(ReadFaceVertex(v[1], context));
                for (int i = 0; i < 2; i++)
                {
                    context.meshFaces.Add(ReadFaceVertex(v[2 + j + i], context));
                }
            }
        }

        private static int ReadFaceVertex(string face, ObjImporterContext context)
        {
            string[] v = face.Split("/");
            return GetIndex(int.Parse(v[0]), context.vertexPositions.Count);
        }

View on GitHub (pinned to 5cab01f7a8)

Solutions

1. Find the offending 'f' line in the OBJ and ensure it lists at least 3 vertices.
2. Re-export the mesh from the source DCC tool.
3. Pre-validate that every 'f' line has >= 3 vertex references before importing.

Example fix

// before
f 1 2

// after
f 1 2 3

foreach (var line in lines)
    if (line.StartsWith("f "))
    {
        var t = line.Split(' ', StringSplitOptions.RemoveEmptyEntries);
        if (t.Length < 4) throw new InvalidDataException($"Degenerate face: {line}");
    }

static bool IsValidFaceLine(string line)
{ var t = line.Split(' ', StringSplitOptions.RemoveEmptyEntries); return t.Length >= 4; }

try { ObjImporter.Load(chunk); }
catch (Exception e) when (e.Message.Contains("Invalid number of face vertices"))
{ /* fix offending 'f' line */ }

When it happens

Trigger: An 'f' line with only two references (e.g., 'f 1 2'); a degenerate face; a face line truncated by editing/export.

Common situations: Malformed OBJs from broken exporters; manual edits that dropped a vertex index; edge-case meshes with degenerate faces.

Related errors

• Invalid vector, expected 3 coordinates, found {v.Length - 1}
• 0 vertex index
• {e.Message}
• 如果项非string类型，则必需设置解析器
• condition number parse error: {text}

AI-assisted analysis of egametang/ET@5cab01f7a8 (2026-08-13). Data as JSON: /api/errors/a50e8ef95bddede5. Report an issue: GitHub.