CadGaragePro 3D scans of trucks and 4x4s · 1:1 · mm

STL vs STEP vs OBJ (and DXF, PDF): Which File Do You Need?

Updated · CadGaragePro

Use STL (or OBJ) when you need the measured shape of a vehicle to design around, STEP when your CAD program needs solids or surfaces, and DXF with a PDF drawing when you are cutting and bending flat parts. Most bumper, rack and canopy jobs combine a scan mesh for reference with DXF files for the cut parts.

What does each file format store?

FormatWhat it storesMesh or solidUnits in the fileTypical useSize in our catalog
STLTriangles only: one normal and three corner points per facet (LoC: STL, binary)MeshNone (FreeCAD)Scan reference, 3D printing76.1 MB to 2,060 MB per scan on sale
OBJVertices, normals, texture coordinates and polygon faces (triangles, quads or larger); color and texture through a separate MTL file (LoC: Wavefront OBJ)Mesh (free-form surfaces are allowed but rare)None (FreeCAD)Colored or textured meshes1,758 MB and 1,898 MB (listings that pair OBJ with STL)
STEP (ISO 10303-21)Solids and surfaces (B-rep), assemblies, or triangles stored as faceted or tessellated geometry (Open CASCADE)Solid or surface, sometimes triangles in disguiseYes, declared in the file (Open CASCADE)Moving CAD models between programs248 MB to 665 MB per STEP listing
DXF2D lines, circles, polylines and splines on layers, with limited 3D (LoC: DXF)2D vectorCoordinates are unitless; the $INSUNITS header states the intended unit (ezdxf)Laser, plasma and waterjet cutting, flat patterns7.5 MB and 11.6 MB (whole plan bundles: DXF, PDF and STEP; the Ranger plan adds IGES)
PDFFixed pages of vector drawing, text and images, standardized as ISO 32000 (LoC: PDF)2D pageWhatever scale and dimensions the drawing statesDimensioned drawings, templates, assembly notesIncluded in the same plan bundles

Why are 3D scans delivered as STL?

A scan is a measured surface, and the simplest way to store a measured surface is as triangles. STL stores nothing else: the binary version is an 80-byte header, a 4-byte triangle count and 50 bytes per triangle (Library of Congress). There are no units, no color in the original specification and no feature history, so there is very little for an importer to misread.

The fixed 50 bytes per triangle makes file size predictable, and these STL-only listings match it:

  • Toyota Hilux N80 open tailgate scan: 1,521,721 triangles, 76.1 MB
  • Hilux N80 front section: 16,060,104 triangles, 803 MB
  • Hilux N80 full vehicle: 39,157,546 triangles, 1,958 MB
  • Isuzu D-Max 3rd gen full exterior: 4,418,118 triangles, 221 MB

Rule of thumb for binary STL: every million triangles adds about 50 MB.

  1. Check the scale after import. STL numbers carry no unit, so your software assumes one (FreeCAD, for example, assumes millimeters, per its import documentation). Measure the overall length and compare it with the scan extent: the Hilux N80 full-vehicle scan is 5,321 mm (209.5 in) long. A result 25.4 times too large or too small means the importer picked inches instead of millimeters, or the reverse.
  2. Work on a lighter copy. A 39-million-triangle vehicle is more than most design tasks need. Crop to the area you are designing around, then reduce it, for example with Blender’s Decimate modifier: in Collapse mode, a Ratio of 0.5 keeps half the faces. Keep the full-resolution file for checking critical mounting points.

Where does OBJ fit?

OBJ holds the same kind of mesh but can also carry texture coordinates, per-vertex color (by convention, not in the core format) and faces with more than three sides (LoC: Wavefront OBJ). For measuring and designing, the container does not change the geometry, so use whichever your software opens more comfortably. A few of our listings include OBJ: the Hilux N80 rear section ships as OBJ and STL (1,758 MB), and in the Toyota Tacoma 3rd gen bundle the bare ladder frame comes as OBJ (1,898 MB in total).

What does “STEP from a scan” really mean?

A STEP file made from a scanned vehicle has no sketches or feature tree, because the shape was measured, not modeled. What it contains depends on how the mesh was converted:

Kind of STEPWhat is insideGood forWatch out for
Surfaced (reverse-engineered)Smooth fitted surfaces joined into a body (advanced B-rep)Offsetting, trimming, sectioning, matching parts to body panelsThe surfaces approximate the scan; ask how closely they follow it
Mesh-wrapped (faceted)Every triangle turned into a flat CAD face (faceted B-rep, or advanced B-rep of flat planes)Opening the shape in CAD programs that will not import meshesMillions of tiny faces: heavy to work with, and offsets or fillets on it are rarely practical
TessellatedTriangles stored directly as tessellated geometry, not as B-rep facesViewing and measuring in software that reads itIt is still a mesh: you can measure it but not edit it like a solid

How to tell which one you have:

  • Click a single face. If the selection is one small triangle, the file is mesh-wrapped.
  • Read the entity names. NIST’s free STEP File Analyzer and Viewer lists every entity in a spreadsheet (names as in the Open CASCADE STEP documentation). faceted_brep_shape_representation allows only flat faces (STEP Tools) and tessellated_shape_representation holds stored triangles. advanced_brep_shape_representation is what fitted surfaces use, but its faces may also be plain planes (advanced_face, elementary_surface), so a body with hundreds of thousands of flat faces is still mesh-wrapped.

You can also make a faceted body from any STL yourself. In Autodesk Fusion, open the Design workspace, Mesh tab, Modify > Convert Mesh. Faceted turns each mesh face into a body face, Prismatic merges groups of faces into single faces on mechanical shapes, and Organic (which requires the Fusion Design Extension) produces an organically shaped body (Autodesk).

Our STEP listings are not small files: the Ford Ranger Next Gen front is 518 MB, the rear 360 MB and the chassis 248 MB, and the Jeep Wrangler JK full vehicle is 665 MB. If a listing does not say which kind of STEP it contains and your workflow depends on it, message the shop before buying.

When do you need DXF and PDF?

DXF and PDF are for the flat parts you will actually cut and bend.

DXF for laser, plasma and waterjet. SendCutSend’s preflight checklist is a useful reference wherever you cut: built at 1:1 scale, preferably in inch or mm units, no open contours, text converted to outlines, all objects on one layer, and stray points and duplicate lines removed (SendCutSend). DXF coordinates are unitless and only the $INSUNITS header says what they mean (4 for millimeters, 1 for inches), so measure a known hole or edge after import before you send a job (ezdxf).

DXF for the press brake. A flat pattern is only correct for the material thickness, inside bend radius and K-factor it was unfolded with. Autodesk defines the K-factor as the neutral axis offset from the inside bend surface divided by the material thickness (Fusion sheet metal rule reference). If your material or tooling differs, unfold again from the 3D model with your own values instead of stretching the DXF.

PDF for people. A PDF fixes the page layout of vector drawings and text, which suits dimensioned drawings, bend directions, assembly order and weld notes. If you print a template from it, print at 100% scale and measure a known dimension before you mark steel.

Both plan listings in our catalog ship all three formats together. The Jeep Cherokee KJ front plan is 7.5 MB and the Ford Ranger Next Gen rear plan is 11.6 MB, each as DXF, PDF and STEP, and the Ranger plan also includes an 8.9 MB IGES file: small next to a scan, because flat profiles need far less data than millions of triangles. Some cutting services take 3D files too; SendCutSend lists .dxf, .dwg, .stp and .step among its accepted formats.

Which files do I need for a bumper, rack or canopy?

ProjectDesign aroundMake the parts withCatalog examples
Front bumperScan of the front end with the mounting points exposedDXF for plates and brackets, PDF drawingHilux N80 engine compartment with the front bumper and crash carrier removed (8,035,626 triangles, 402 MB); Jeep Cherokee KJ front plan (DXF, PDF, STEP)
Rear bumperScan of the rear crossmember and bumper mounting faceDXF, PDFJeep Cherokee XJ rear bumper area bundle (458 MB); Ford Ranger Next Gen rear plan (DXF, PDF, STEP, IGES)
Roof rackFull-vehicle exterior scan including the roofDXF for plates and mounts, PDFToyota Land Cruiser 200 with roof rails (2,060 MB); Toyota Land Cruiser Prado 150 with roof rails (1,947 MB)
Canopy or bed rackScan of the bed, rails and cab backDXF for sheet panels, PDFFord Ranger Raptor PX3 bed with bedliner and tailgate open (2,387,211 triangles, 119 MB); Hilux N80 rear section, bed inside and out (OBJ and STL)
Sliders and recovery pointsFrame scan or STEPDXF, PDFFord Ranger Next Gen chassis STEP (248 MB); Tacoma 3rd gen bare frame (OBJ)

Each plan page names the parts it builds (a rear bumper; a winch plate and skid plate); read the Etsy listing for the full parts list.

A simple way to decide:

  • Choose STL if your software handles meshes and you mainly need positions, mounting faces and clearances.
  • Choose STEP if your CAD program cannot use meshes or you need surfaces to build on, and confirm which kind of STEP it is.
  • Choose a plan (DXF, PDF and STEP; one plan adds IGES) if you want to cut and build an existing design rather than draw your own.

Front bumpers bolt to the vehicle’s crash structure and can sit near airbag crash sensors, so check the maker’s guidance and your local road rules before fitting one. Keep roof racks and their loads within the vehicle’s roof load rating, and have structural welds done by someone qualified for the material and process.

Sources

Scans mentioned in this guide