How to prepare CAD files for 3D rendering
Send STEP or native CAD at full precision, include the parts you cannot see, supply artwork as vector with dielines, and say what the real-world dimensions and finishes are. Engineering CAD is built for manufacturing, not for a camera — the gap between those two jobs is where most rendering delays come from.
Which formats actually work
STEP (.stp/.step) is the safest interchange format and the one to send if you are unsure — it preserves true surfaces rather than an approximation of them. IGES works but is older and more prone to gaps. Native Solidworks, Rhino, CATIA and Creo files are all usable and often better than an export, because nothing has been converted yet. OBJ and FBX are fine when the model is already a mesh, though a mesh exported at low resolution cannot be recovered — curves become visible facets and no amount of smoothing will put the geometry back.
Why engineering geometry needs work before it renders
CAD is built to be manufactured, and that produces geometry a camera dislikes. Perfectly sharp edges are the biggest one: nothing in the physical world has a zero-radius edge, and a real edge catches a thin highlight along its length. A model without edge treatment reads as computer-generated instantly, and adding it back is real work. Assemblies also tend to arrive with interpenetrating parts, mirrored components with flipped normals, and hundreds of fasteners that will never be seen but still have to be processed. None of this is a problem — it is expected — but it is why "we already have the CAD" does not mean the build is free.
The checklist
- STEP or native CAD, exported at the highest available precision
- Real-world dimensions, or a drawing with them on it — scale is not always reliable in an export
- Assemblies with parts named, not a single merged solid
- Internal parts included if anything is transparent or will be cut away
- Label and packaging artwork as vector (AI, PDF, EPS) with the dieline
- A finish list: gloss, matte, soft-touch, anodised, brushed, foil — per part
- Pantone or hex values for every colour that has to be exact
- Reference photographs of the physical product if one exists
- Any existing product photography you want the renders to match
What to send when there is no CAD
Most projects that start without CAD still go ahead — it just moves cost into modelling. Photographs of the physical product from six angles (front, back, both sides, top, bottom) plus a dimensioned drawing or even a tape measure and a note is enough to build from accurately. For packaging, a flat dieline plus the container dimensions is often better than a photograph, because the vessel is a known shape. Send whatever exists rather than waiting until something better does; the quote gets more accurate with more information, not less.
The things that most often delay a project
A merged solid with no part separation, so nothing can be assigned a different material. Artwork supplied as a flat JPEG of the finished pack rather than as vector with a dieline, which means the label cannot be wrapped correctly and type goes soft. Missing colour references, which turns a two-day approval into a week of back and forth. And a model exported as a low-resolution mesh, which is the only item on this list that cannot be fixed without going back to the source.
Questions
What is the best CAD format to send for rendering?
STEP, exported at the highest precision your software offers. It preserves true surface geometry rather than a faceted approximation, and every rendering pipeline reads it.
Do you need the internal components?
Only if they will be seen — which includes anything behind transparent housing, anything in an exploded or cutaway view, and anything visible through an opening. If the product is opaque and stays assembled, the outer shell is enough.
Can you work from a low-poly or game-ready mesh?
Sometimes, but it is the worst starting point. Detail removed at export cannot be recovered, and curved surfaces come back as visible facets. If the original CAD still exists anywhere, send that instead.
How should we send packaging artwork?
Vector — AI, PDF or EPS — with the dieline, so it can be wrapped onto the container properly. A flat JPEG of a finished pack cannot be applied accurately to a curved surface and the type will not hold up.
We have no CAD at all. Can you still render our product?
Yes. Photographs from six angles plus dimensions are enough to model accurately, and a physical sample is better still. It shifts cost into the build stage, which is worth knowing before you compare quotes.