Web-based — works everywhere
No download, no Windows VM on your Mac, no installer that fights a new OS version. Open a browser, sign in, and your designs are there. Updates ship continuously instead of never.
GemDiagram vs GemCAD
GemCAD is the program nearly every faceter learned on — the de-facto standard, with thousands of cutting designs saved in its format. But it's a retired Windows desktop app with flat wireframe diagrams. GemDiagram runs in your browser on any OS, opens your existing GemCAD files, and renders them as realistic 3D stones with full color, fire, and refraction.
Coming from GemCAD? Your files come with you
Already have GemCAD files? Open a .gem or .asc straight in GemDiagram — drag it in and watch it render in 3D. The tiers, angles, indices, and (where present) the refractive index come across; if the file names no material, GemDiagram snaps to the closest of its 22 built-in materials by RI. Imports open read-only — click Save to keep it as an editable .facet file.
GemDiagram vs GemCAD, feature by feature
An honest, side-by-side look. Where a row is marked “coming soon” or carries a plan name, that reflects exactly what GemDiagram ships today.
| Feature | GemDiagram | GemCAD |
|---|---|---|
| Runs in your browser — nothing to install | ✓ | ✗ |
| Works on Mac, Windows, Linux & Chromebook | ✓ | Windows desktop only |
| Realistic ray-traced render (color, fire, refraction) | ✓ | ✗ |
| Live 3D preview while you design | ✓ | Wireframe / 2D diagrams |
| Rough Planner — best-yield orientation search | ✓ | ✗ |
| Cutting Assistant — step-by-step at the machine | ✓ | ✗ |
| Opens your existing GemCAD files | .gem, .asc | — |
| PDF cutting report | ✓ | ✓ |
| Frosted-facet preview | Pro | ✗ |
| Screenshot & video export | Studio / Pro | ✗ |
| Client Preview link to show buyers their stone | Pro | ✗ |
| Actively maintained & updated | ✓ | ✗ |
| Price | Free tier, paid from $20/mo | Free (legacy freeware) |
Why cutters switch to GemDiagram
See the actual stone, not a wireframe
GemDiagram's Realistic render ray-traces color, dispersion (fire), and internal refraction so you judge how a design will really look — then Ray Studio lets you trace individual light rays through it.
Plan the rough, not just the facets
The Rough Planner searches orientations for best yield from a piece of rough, and the Cutting Assistant walks the cutting sequence tier by tier at the machine — workflow GemCAD never covered.
Show clients the result
Export screenshots and video, and (Pro) generate a Client Preview link that shows a buyer their rough with the finished gem inside it plus a rotating render — something no desktop faceting tool offers.
Where GemCAD still has the edge
No tool wins on everything. Here's where GemCAD is the stronger choice.
A massive existing design library
Decades of published cutting designs exist as .gem/.asc files. GemDiagram opens them — but GemCAD is where most of that catalogue was authored.
Fully offline native app
GemCAD runs entirely on your machine with no account. If you work somewhere with no internet and want a self-contained desktop binary, that's its home turf.
What cutters already know
It's the tool a generation of faceters trained on. The muscle memory and community know-how around GemCAD are real.
Common questions
Yes. Import a
.gem or .asc file from the top bar and it renders in 3D immediately. The geometry (tiers, angles, indices) and any refractive index come across; save it as a .facet file to edit it in GemDiagram.GemDiagram's Free plan previews designs in 3D at no cost and without a card. Importing, editing, and exporting your own files is included from the Starter plan at $20/month.
GemCAD is a Windows desktop application; modern Mac users typically need a Windows emulator. GemDiagram runs in any browser, so it works natively on macOS, Windows, Linux, and Chromebooks.
GemCAD is long-established but no longer actively developed. GemDiagram is in active development with new features shipping to the browser.