egametang/ET · critical · Exception

rcBuildPolyMesh: The resulting mesh has too many polygons {m

Error message

rcBuildPolyMesh: The resulting mesh has too many polygons {mesh.npolys} (max {MAX_MESH_VERTS_POLY}). Data can be corrupted.

What it means

The post-condition check at RecastMesh.cs:1206 verifies mesh.npolys does not exceed MAX_MESH_VERTS_POLY (65535) at the end of the primary rcBuildPolyMesh path. Exceeding it means the 16-bit polygon index fields overflowed, so the returned mesh may be corrupted.

Source

Thrown at Packages/cn.etetet.recast/Scripts/Core/Share/Recast/RecastMesh.cs:1206

                            mesh.polys[p + nvp + j] = 0x8000 | 2;
                        else if (mesh.verts[va + 2] == 0 && mesh.verts[vb + 2] == 0)
                            mesh.polys[p + nvp + j] = 0x8000 | 3;
                    }
                }
            }

            // Just allocate the mesh flags array. The user is resposible to fill it.
            mesh.flags = new int[mesh.npolys];

            if (mesh.nverts > MAX_MESH_VERTS_POLY)
            {
                throw new Exception("rcBuildPolyMesh: The resulting mesh has too many vertices " + mesh.nverts
                                                                                                 + " (max " + MAX_MESH_VERTS_POLY + "). Data can be corrupted.");
            }

            if (mesh.npolys > MAX_MESH_VERTS_POLY)
            {
                throw new Exception("rcBuildPolyMesh: The resulting mesh has too many polygons " + mesh.npolys
                                                                                                 + " (max " + MAX_MESH_VERTS_POLY + "). Data can be corrupted.");
            }

            return mesh;
        }

        /// @see rcAllocPolyMesh, rcPolyMesh
        public static RcPolyMesh MergePolyMeshes(RcTelemetry ctx, RcPolyMesh[] meshes, int nmeshes)
        {
            if (nmeshes == 0 || meshes == null)
                return null;

            using var timer = ctx.ScopedTimer(RcTimerLabel.RC_TIMER_MERGE_POLYMESH);

            RcPolyMesh mesh = new RcPolyMesh();
            mesh.nvp = meshes[0].nvp;
            mesh.cs = meshes[0].cs;
            mesh.ch = meshes[0].ch;

View on GitHub (pinned to 5cab01f7a8)

Solutions

Tile the navmesh (rcConfig.tileSize) so each tile's polygon count stays far below 65535.
Raise maxVertsPerPoly to reduce polygon count per contour.
Raise cellSize / contourSimplificationError to coarsen geometry.
If building a merged mesh (MergePolyMeshes), confirm inputs aren't already near the limit.

Defensive patterns

Strategy: validation

Try / catch

try { rcBuildPolyMesh(ctx, cset, nvp, out mesh); }
catch (Exception e) when (e.Message.Contains("too many polygons") && e.Message.Contains("Data can be corrupted")) {
    Log.Error($"Corrupt polymesh: {e.Message}");
    // discard mesh, re-bake with coarser config or smaller tiles
}

Prevention

Cap per-tile polygon count in bake config.
Never consume a mesh that triggered a 'Data can be corrupted' throw.
Run automated bake-size assertions on level content.

When it happens

Trigger: Fires immediately after the nverts check at :1200 in the same finalization block, when mesh.npolys > 65535 after all polygon storage is complete.

Common situations: Massively polygon-heavy navmesh from a huge or untiled level; low maxVertsPerPoly combined with dense contours; often co-occurs with error 302. Indicates the conservative maxTris guard (301) was not the binding constraint but the final 16-bit cap was.

Related errors

AI-assisted analysis of egametang/ET@5cab01f7a8 (2026-08-13). Data as JSON: /api/errors/b6ec65cfe79105b4. Report an issue: GitHub.