Render STL jewelry files with real metals and stones

What an STL file contains

STL describes a shape as a set of triangles and nothing else. It stores no colours, no materials, no units and, in practice, no part names. That is perfect for printing a wax or resin model, because a printer only needs the shape. For rendering, it means the studio receives one solid surface.

Every CAD program used in jewelry can export STL, including JewelCAD, Rhino, MatrixGold, 3Design, ZBrush and Blender, which is why STL is often the file a freelance designer or a factory sends you.

How STL works in the studio

An STL file opens as a single part that starts as metal. You can choose any of the 98 metal presets, from polished yellow gold and 22K gold to brushed white gold and platinum, and the whole piece takes that material. For metal-only designs such as plain bands, chains, cufflinks and many pendants, that is all you need.

Because an STL file has no separate parts, stones cannot get their own gem material. A ring with a diamond will render as one metal surface, including the diamond. If the stones matter in your images, ask for the file in a format that keeps separate named parts.

When to ask for OBJ, GLB or 3DM instead

Most CAD designers can export several formats in a minute, so it is worth asking. See our pages on GLB, OBJ and 3DM.

Print files are often heavy

STL files made for printing are exported at very high resolution, because a printer reproduces every facet. A single ring can easily reach tens of megabytes. Files can be up to 100 MB, and a lighter file opens faster in the studio. If your STL is over the limit, export it again at a lower resolution, or reduce it with a decimation tool. A render needs far fewer triangles than a 25 micron print.

Units and scale

STL files do not store units. A ring modelled in millimetres and the same ring in inches look identical to the studio, because it frames the camera around the model automatically. Units only matter for printing and casting, not for rendering.

Fixing common STL problems

1. Dark patches or holes. Some triangles face inwards. Repair the mesh in your CAD software or a mesh repair tool, then export again.
2. Faceted curves. The export resolution was too low. Increase it slightly for smooth shanks and bezels.
3. Supports included. Print supports sometimes stay in the file. Remove them before exporting a render copy.
4. Too large to upload. Lower the export resolution or decimate the mesh.

A practical workflow for STL

1. Upload the STL to your library. A preview is created right away.
2. Open it in the studio and choose a metal that matches the casting alloy.
3. Pick lighting, background and ground, then a pose such as three-quarter front.
4. Export stills for approval, or a 360° video to send to the client.

This makes STL files useful long before casting. A customer can approve a design from a realistic gold render instead of a grey printed wax. Read our guide to STL files for jewelry for more on preparing print files for renders.