How to prepare jewelry CAD files for rendering

Why preparation decides render quality

Most rendering problems start in the CAD file. Stones that render black, gold that bleeds into a diamond, faceted surfaces on a polished band and models that load at the wrong size are almost always file problems, not lighting problems. Ten minutes of preparation saves hours of fixing, whether you render yourself or send files to someone else.

This checklist works for any renderer. The notes about layer names and formats also explain exactly how RenderMyJewels reads your files, so most models are right the first time you open them.

The checklist

1. Every stone is a separate object from the metal.
2. Layers or objects have clear names, with stone words only on stones.
3. The model is at real-world size in millimetres.
4. Meshes are closed and normals face outwards.
5. The polygon count is reasonable for rendering.
6. Construction geometry, cutters and supports are removed.
7. Metal parts are grouped so you can colour them separately.
8. The file is exported in the right format.
9. One test file is checked before you export the whole range.

1. Separate every stone from the metal

A renderer needs to know which surfaces are metal and which are gem. If a stone is merged into the head or shank, it gets the same material as the metal and the sparkle is gone. Keep each stone as its own object, even in pavé. Group pavé stones by size if you like, but never boolean them into the metal.

Prongs should touch stones, not pass through them. Intersecting geometry creates dark seams and strange refractions. Check the seat of each stone too: a girdle buried deep in the metal or floating above the prongs looks wrong in close-ups.

2. Name layers so materials apply themselves

Clear names make materials quick to assign and prevent mistakes in large files. Use names that say what each part is.

RenderMyJewels reads these names when you upload. Layers or meshes whose names contain words such as Diamond, Gem, Stone, Ruby, Sapphire, Emerald, Pavé or Halo are treated as stones automatically. Other parts usually start as metal. You can switch any layer between metal, gem and hidden in the studio, but good names save that step.

A naming convention you can copy

One trap is worth knowing. Because stone words are matched anywhere in a name, a metal part called Halo or Stone Setting would be read as a stone. Call metal parts Frame, Bezel, Head or Setting instead, and keep stone words for stones.

3. Model at real-world scale

Jewelry CAD is usually modelled in millimetres. A ring that was exported in metres or centimetres can load tiny or huge, and lighting will not behave as expected. Check the units before export, and keep them consistent across your range so every model loads at a similar size. Consistent scale also makes it easier to show size honestly. See how to show jewelry scale.

4. Close the gaps and fix normals

Every surface needs a clear inside and outside. In a mesh, that direction is the normal. Inverted normals make metal look dark or inside out and turn stones black.

• Join surfaces into closed solids before meshing.
• Check for naked edges and close them.
• Unify normals so they all face outwards.
• Delete duplicate surfaces sitting on top of each other.

Duplicate surfaces are a common hidden problem. Two identical surfaces in the same place flicker or show a speckled pattern, usually after parts were copied between files.

5. Choose a sensible polygon budget

Renderers work with meshes. When you export from a NURBS modeller such as Rhino, curved surfaces are converted into triangles. Too few triangles and polished curves look faceted. Too many and files get heavy without looking any better.

As a rough guide, most rings and pendants look smooth well under 300,000 triangles. Spend triangles where reflections show, such as the outside of the band and the bezel, and keep stones at their true facet count. In Rhino, use a custom render mesh with a smaller maximum angle for smooth reflections on curved, polished surfaces.

6. Remove what should not render

Before export, delete or hide anything that is not part of the finished jewelry:

• construction curves and guide lines,
• stone cutters and boolean helpers,
• hidden duplicate parts and old versions,
• dimension annotations and text,
• support structures and sprues meant for printing or casting.

Exporting only selected objects or visible layers keeps files small and clean.

7. Group metal parts logically

Two-tone pieces are common, such as a white gold head on a yellow gold shank. If the head and shank are separate objects, you can give them different metals in seconds. If they are merged, you have to go back to CAD. Group parts the way the piece is made and finished, and you can show every metal combination later without touching the file again. See variants and colourways.

8. Pick the right export format

STL is the weakest choice for rendering because it stores a single mesh with no names or parts, so metal and stones cannot be told apart. If your workflow is built around STL for printing, export a GLB, OBJ or 3DM copy for rendering. See STL files for jewelry.

A note on glTF: a glTF that stores its data inside one file works fine. A glTF that points to a separate .bin file or texture folder cannot be read from a single upload, so export GLB instead.

In RenderMyJewels you can upload files up to 100 MB, or 200 MB for 3DM and FBX, and there is no limit on how many models you upload.

Exporting from Rhino and MatrixGold

Rhino

1. Show only the layers that belong to the finished piece.
2. Select the visible jewelry objects.
3. Use Export Selected and choose 3DM to keep layers, or GLB for a compact mesh.
4. For GLB, adjust the mesh settings so curved surfaces stay smooth.

MatrixGold

MatrixGold runs on Rhino, so the same export options apply. Gems placed with MatrixGold's gem tools are separate objects, which is exactly what a renderer needs. Rename gem layers with clear stone words before export. For a full walkthrough, see from Rhino to render.

Other CAD software

JewelCAD, 3Design, ZBrush and Blender all export formats that render well. Export OBJ, FBX or GLB where possible so parts stay separate, and check the scale on the first file. See the software guides for Rhino, MatrixGold, JewelCAD, 3Design, ZBrush and Blender.

Common file problems and quick fixes

Test before you export a whole range

Export one representative piece first, ideally the most complex. Upload it, check that stones and metal were picked up correctly, look at it from several angles and render a quick test image. Fix anything once in your template file before exporting the rest of the collection. When you are ready for the full range, the bulk uploader takes a whole folder at once and can read SKUs from file names. See the model library and bulk upload.

Summary

A render-ready jewelry file has separate, well-named stones and metal parts, real-world scale, closed meshes with outward normals, a sensible mesh density and nothing extra in it. Export 3DM or GLB for the best results and test one file before batching. Get this right and rendering becomes a quick materials and export job rather than a repair job.