Binary STL Mesh Inspector

How to use Binary STL Mesh Inspector

Find the triangle count, decoded vertex bounds and unpaired-edge evidence in a small binary STL before choosing a separate modeling tool. This inspector reads the actual fixed-length records, including files whose arbitrary binary header starts with solid. It produces an evidence report rather than a repaired model or a 3D preview.

1. Choose a local binary STL or load the original unit-tetrahedron example. Set the complete geometry JSON or per-facet CSV format.
2. Run the inspector. Review source-unit extents, the area approximation, degenerate/duplicate facets and edge-incidence counts together with their limitations.
3. Download the complete bounded report. Use separate modeling software for rendering, unit assignment, self-intersection checks or repairs. Reset clears the current result.

Good to know

• Binary STL only: exactly 84 + 50 × the declared triangle count, from 0 through 20,000 triangles and 84 through 1,000,084 bytes. Trailing bytes, truncated records, ASCII STL and nonfinite stored normals or vertices are refused atomically. A binary header beginning solid is accepted when the exact binary structure fits.
• Each decoded vertex coordinate has magnitude at most 1,000,000,000. IEEE float32 values are represented as numbers, with positive and negative zero both reported as 0. Vertex matching and extent endpoints use exact decoded values, without tolerance welding; extent-size differences use binary64 arithmetic. Empty files with a valid zero count have no extents and no applicable edge pairing.
• STL supplies no reliable physical scale. Every dimension uses unknown source units; area uses their square and algebraic volume their cube. No millimeter/inch choice, density, weight, building rule or engineering accuracy is inferred.
• Area and each displayed tetrahedron contribution are binary64 approximations. The total signed algebraic determinant fraction is exact for decoded float32 vertices relative to origin [0,0,0]. Open meshes depend on that origin and reversed winding changes the sign. This is not certified solid volume, even if every edge is paired.
• Edge incidence and edge-connected face components exclude zero-area facets. Duplicate triangles are counted regardless of winding but remain in area and determinant totals. More than two edge incidents and same-direction pairs are reported. Vertex-manifold links, T-junctions, self-intersections, overlapping shells and printer readiness are not checked.
• All 80 header bytes are included as hex, and each unsigned 16-bit attribute is retained without interpreting vendor color conventions. The summary shows at most 32 ascending attribute-count entries and declares omitted values; JSON includes the full count inventory. Stored normals are compared with geometric direction but are not trusted, normalized or repaired. JSON contains complete source coordinates and edge evidence; CSV contains all facet rows. Downloads may expose information in the selected source.
• One local File read has a 5-second deadline. A same-origin module Worker has 10 seconds to prepare and a separate 2-second computation deadline. Complete output is capped at 20 MiB. Reset discards the UI result; it does not claim immediate cancellation of an already reading File or already running computation. Pagehide stops waiting for the read and prevents it from later starting a Worker; it does not abort the browser's underlying File promise. An active Worker terminates after settlement, deadline or pagehide.
• No viewer, repair, STL rewrite, material interpretation, automatic storage, account, upload or remote geometry service is used. The original file is unchanged. Limits bound known buffers and record counts, not an asserted browser-heap guarantee.