What ClassNK's 3DMBA guidelines mean if you still work in 2D

ClassNK released its Guidelines for 3D Model-Based Approval — 3DMBA — in May 2026, alongside the simultaneous launch of NK-PASS, the society's 3DMBA-compatible drawing approval and submission platform. For a design office that still delivers PDFs and DXF files, the instinctive response is to file it under "not yet relevant." That response is understandable but slightly wrong. The guidelines don't mandate a migration, and they set no deadline for abandoning 2D submissions. What they do is define the formal structure of the 3D approval route — its scope, its mechanics, and the specific role that 2D drawings play during the transition. Those definitions matter now, because they tell you what you are being transitioned toward and on what terms.

The guidelines were developed through a joint pilot test involving ten Japanese companies. That provenance is worth noting before any analysis of the content: this is not a position paper or a concept document. Ten organisations ran real approval workflows through the regime and reported back. ClassNK has stated that the guidelines will be reviewed and updated based on operational feedback — which is an honest acknowledgement that v1 has rough edges, but also confirmation that the regime is live and will iterate rather than stall. The practical question, for a 2D office, is not whether to engage with this shift but on what terms — and the guidelines define those terms precisely enough that you can locate your current position within the transition. The question is whether the transition period buys you what you think it does.

On scope: the guidelines address four substantive areas. The first is what design information falls within the scope of model-based approval — not everything in a 3D model is subject to class review, and the guidelines define the boundary. The second is submission units: how a 3D model is packaged and presented for review, which is a non-trivial problem when a model contains far more information than any single drawing set. The third is the handling of design changes and revisions — the approval workflow that 2D offices have optimised over decades, and which becomes structurally different when the authoritative record is a 3D model rather than a drawing revision cloud. The fourth, and most immediately relevant for a 2D office, is the defined relationship between 3D models and 2D drawings during the transitional phase.

That relationship is specific, and it is easy to misread. During the transition, 2D drawings may be used as supplementary documentation alongside 3D models submitted through the 3DMBA route. This is not a statement that 2D submission continues unchanged in parallel. It is a description of how the 3D route accommodates offices and projects that are not yet fully model-based: the 3D model carries the approval, and 2D drawings serve a supporting function within that framework. An office submitting entirely in 2D through conventional channels is not operating under these guidelines at all — the guidelines govern the 3D route, not the legacy route. The distinction matters because it reframes what the transition period actually is. It is not a window during which you can watch and wait with no consequences. It is the period in which the 3D route becomes operational and begins accumulating a track record, while conventional 2D submission persists as the prior state rather than the endorsed one.

The format question flows directly from this. OCX — Open Class 3D Exchange — is the international standard format for 3D ship design data specified under these guidelines. ClassNK 3DViewer enables reviewing OCX-format models within the approval process. If your CAD environment cannot export OCX, you cannot participate in the 3DMBA route, which means the transition period is not available to you in the way it is to offices that can. This is the near-term toolchain question the guidelines implicitly raise for any design office evaluating where it stands: not whether to move to 3D in principle, but whether your current environment could produce an OCX-format submission if a client or a project required it. Many offices will find the honest answer is no — and the guidelines make clear that this is the format the approval architecture is being built around.

What the ten-company pilot test produced, in the end, is a defined and operational framework with a stated commitment to revision. For a chief engineer running 2D workflows, the most useful reading of the guidelines is probably this: the transition period is real, but it describes a 3D-led world in which 2D plays a documented secondary role, not a stable plateau where both approaches carry equal standing. ClassNK has done the work of defining the new regime precisely enough that you can locate your office within it. That precision is the document's primary value.