CAD Conversion

Overview

realvirtual WEB reads STEP and JT files directly in the browser. That works well up to a point: a browser tab has a fixed memory ceiling, and a large assembly hits it. When a gateway is available, the viewer hands the file to CONNECT instead — the gateway converts it natively, with no such ceiling, and returns a GLB.

The file never leaves the machine. CONNECT runs locally, and there is no cloud service involved in the conversion.

Using it

Import the file in the viewer as usual. When the file is too large for the browser path and a gateway is reachable, the viewer offers the via CONNECT route and shows the conversion progress. The result is loaded into the scene and cached.

Nothing has to be configured for this. The gateway reports on its status whether it can convert STEP and JT at all, and the viewer offers only what is actually available.

Note

The conversion service belongs to the gateway, but the CAD import itself is part of the Editor — a commercial feature of realvirtual WEB. The bundled open-source viewer therefore offers no import to route through this service; see where the viewer comes from.

STEP

STEP assemblies are tessellated with OpenCASCADE. Assembly structure, part names and colors are preserved, and the output is standard glTF — meters, Y-up.

Two settings make the result usable in a browser, both on by default:

• Face merging collapses the many per-face primitives of a CAD body into one primitive per body. A large assembly drops from tens of thousands of draw calls to a few hundred, while every body stays its own selectable node.
• Draco compression shrinks the GLB by roughly a factor of 10 to 20.

Together this turns a 161 MB assembly into a GLB of a few megabytes instead of a hundred.

The tessellation tolerance comes from the quality preset chosen in the viewer — finer presets mean more triangles, a larger file and a longer conversion.

JT

JT files — the tessellated format Siemens NX and Teamcenter export — are converted by the same reader that powers the browser path, so both routes produce the same geometry.

Two differences to STEP are worth knowing:

• No progress percentage. JT decoding reports nothing measurable while it runs, so the viewer shows an indeterminate indicator instead of a progress bar.
• No tessellation settings. JT is already tessellated. The only choice is which level of detail to take out of the file.

A running JT conversion can be cancelled, which frees the conversion slot immediately.

Caution

Export monolithic JT files. A shattered JT — an assembly whose parts live in separate files — is not reliably detected. Such a file either fails as unreadable or converts to an incomplete model without a warning.

Caching

Results are cached by the content of the file plus the chosen quality. Re-importing the same file is instant. When the converter itself is updated, old cache entries are invalidated automatically, so an improved converter never serves you yesterday’s geometry.

Limits

The maximum file size depends on the license and applies per file:

Tier	STEP	JT
Community	25 MB	12 MB
Annual, Lifetime	unlimited	unlimited

A gateway’s own configuration can lower these limits further but never raise them. An oversize upload is refused with a message that names which limit applied — the license or this gateway’s configured capacity.

Importing several files in one session is fine as long as each individual file is within the limit. See licensing.

Resource use

STEP and JT conversions share one conversion slot, because the limit protects one machine — two heavy converters running at once would not. Each conversion runs as a separate process: an out-of-memory condition on a huge assembly ends that conversion, never the gateway.

Long-running conversions are stopped after a configurable timeout, by default 15 minutes.

See also

• Licensing — where the size limits come from
• First connection — loading a model