How it works

1. Your model is one open file

Everything you model in gomodl — members, sections, plates, bolts, holes, copes and cuts, piece marks, assemblies, grids, levels, RFIs and notes — is kept in a single IFC file.

IFC (Industry Foundation Classes) is the open, international standard for describing buildings and structures, published as ISO 16739 and looked after by buildingSMART International. It is not ours and it is not tied to any one software company. Think of it as the PDF of building models: a file that any compliant program can open, whoever made it. gomodl writes IFC4 ADD2, the version most BIM software reads today.

That file is the model. gomodl does not keep a private copy in a format of its own, so there is nothing to convert and nothing locked away. You can download it whenever you like and open it in BIMvision, Navisworks, Autodesk Viewer, Solibri or any other IFC viewer.

Going the other way is more limited, and it is worth being clear about it. You can import an IFC file from another detailing package, and gomodl will bring in its steel, plates, holes and bolts and recognise copes and end cuts where it can. What it cannot bring in is the other package’s intelligence: its connections arrive as loose plates and bolt groups rather than as editable gomodl connection macros, its bolt and weld specifications do not map onto your gomodl libraries (bolts are matched by diameter where a library bolt fits), and its welds do not come across. An imported model is a solid starting point to check, issue or build on — to detail a joint the gomodl way, remove the imported plates and apply a gomodl connection to it.

2. Where it is kept

When you save, your browser writes the model out as an IFC file and sends it to our cloud storage. It is kept there as a single file — an “object” in an object store, the same kind of storage that sits behind most modern cloud services.

Alongside it, a small database holds only the details about each project: its name, owner, dates and member count. No geometry lives in the database. There are no hidden tables of beams and columns that could quietly drift away from the file — the IFC file is the one and only source of truth.

3. Drawings are made when you open them

Fabrication, fitting, shop-assembly and GA sheets are not stored as separate drawings that have to be kept in step with the model. Each sheet is worked out from the model at the moment you open it, in your browser — projected, dimensioned and laid out on the sheet in a few seconds.

That has three useful consequences:

• Drawings cannot go stale. Move a member and its sheets move with it. There is no “regenerate all drawings” step to forget.
• A drawing cannot disagree with the model, because it is produced from the model. If something is not in the model, it is not on the sheet.
• Storage stays small. One file per model, rather than one per sheet per revision.

While you are working, the app may keep a small IFC file for each fabrication sheet so that it does not have to redo work it has already done. That is a shortcut made from the model, never a second version of it.

4. A freeze is a fixed record

When you freeze a revision for approval or construction, gomodl copies the model at that moment into a new IFC file under its own revision. From then on, the app never writes to that file again.

• At the moment of freezing, gomodl records a digital fingerprint of the file (a SHA-256 hash). Any change to the file, however small, would give a different fingerprint. It is also how gomodl knows when nothing has changed — freezing an identical model twice is refused.
• A freeze stores that one model file plus its preview images. Every drawing, register and NC1 file in it is produced from the frozen file whenever someone opens or downloads it, so the sheets always describe exactly the steel that was issued.
• You can still change who can see a freeze, mark it superseded, or delete it. You cannot edit what is inside it. Further changes become the next revision.

One honest note. The model in a freeze never changes, but the software that draws it keeps improving. A sheet opened again months later is drawn by the current version, so its presentation can improve — a dimension placed more clearly, say — while the steel it describes cannot change. The PDFs you downloaded and sent at the time remain your record of exactly what went out, so keep them.

5. Your browser does the heavy lifting

The 3D model, the geometry of every cut and cope, hidden-line drawings, dimensioning and PDF creation all run on your device, not on our servers. Our servers mostly store files and look after accounts. That is what lets gomodl run anywhere without an install, stay responsive while you work, and never make you queue behind someone else’s job.

It also means the browser and the device you use make a real difference. A current browser on a reasonable machine is the single biggest thing you can do for a smooth experience — see section 7.

6. Where you can use it

Windows and Linux PCs

Full modelling, detailing and drawing in any current browser.

Apple silicon Macs

gomodl runs on M-series Macs in Safari, Chrome, Edge or Firefox, with nothing to install. That matters: most established steel detailing packages run only on Windows, so on a Mac they mean a Windows virtual machine or a second computer. With gomodl a MacBook or Mac mini is simply a detailing workstation.

Tablets

On a good modern tablet — an iPad, or an Android tablet with a current Chrome — you can open projects and freezes, orbit the 3D model, and pinch and pan around GA and fabrication sheets. Selection has a tap-to-select mode built for fingers, so no mouse or keyboard is needed. Modelling works too, and is quicker with a keyboard and mouse or trackpad attached. A tablet goes on site and onto the shop floor far more easily than a laptop, and the same issued drawings are on it.

Phones

A phone is the quickest way to check a frozen revision on site: open the shared link, look at the 3D model, find a GA or a fabrication sheet. The modelling canvas does run on a phone, but it is not designed for detailing on a small screen.

7. Getting the best experience

A guide, not a set of hard limits:

8. Built on open-source software

gomodl stands on the work of a great many people who give their software away. We are grateful to every one of them. The main projects we use, and the licences they are shared under:

Models, geometry and 3D

Drawings and documents

The application

Servers and storage

This website

And the IFC standard itself, from buildingSMART International, which is what makes an open model possible in the first place. Each project remains the property of its authors and is used under its own licence.