TopMod 3D's mobile and browser-oriented topological modeller moved through versions 4.0, 4.1 and 4.2 within days. Apple's primary release history says 4.0 added multi-viewport CAD-style work, dimensions, smoothing and a Claude-based model builder; 4.1 extended subdivision operations to open surfaces and added generators; and 4.2 introduced a building-brick module, ASET light-return maps, new material views and editable growth operations. This is more precise than the 'v3' label used by an October 24 trade-press article.

What remains from the original TopMod?

TopMod's research foundation is consistent topological editing of two-manifold polygon meshes. Texas A&M describes a system in which inserting and deleting edges creates handles, holes and connected surfaces while preserving topological consistency. That does not mean every export is automatically manufacturable: a closed manifold surface is only the first digital gate.

The current app combines that foundation with touch interaction, a live modifier stack and generative tools. The developer says it runs on iPhone and iPad and exports OBJ; the trade coverage also describes browser and Rhino 8 connections. The App Store lists the app as free, requiring iOS 17 or later and providing an English interface.

What the 4.0–4.2 sequence adds

Version 4.0 lists one, two or four viewports, per-view display settings, dimensions and units, face push/pull, fillets and chamfers. The Claude assistant requires the user's own Anthropic key, so AI is not a keyless local base feature. Version 4.1 adds exact value entry, cage editing, Voronoi, gyroid, Menger and other generators, plus topology-optimisation and airflow views. Version 4.2 lists a brick module with layer-by-layer instructions, gemstone analysis views and more procedural operations.

Those names describe a broad creative toolkit, not validated engineering simulation. Public release notes provide no solver version, boundary-condition treatment, convergence study, reference problem or validation error for the finite-element, aerodynamic or topology-optimisation tools. Safety- or performance-critical decisions therefore require separate validated CAE and physical testing.

Scope of the AI assistant

Claude integration may help turn equations or instructions into an editable operation chain. Retaining steps as modifiers can make parameter changes more traceable than a one-shot opaque mesh. A language model can still propose a wrong equation, unit or manufacturing condition. Its output is a design proposal, not an approved product definition.

Gates before 3D printing

At least five checks belong after export: a closed and consistently oriented mesh; no self-intersections or degenerate triangles; dimensions and units matched to the source; minimum walls, gaps and overhangs appropriate to the selected process; and layer preview plus a trial build showing that generated detail survives. OBJ handling can separate units and manufacturing metadata, so a controlled 3MF job package should be created in the slicer.

Open source and reproducibility

Historic TopMod code is available through GPL-licensed mirrors, while current trade coverage calls the new platform open source. Publicly discoverable old TopModLab and erjiang repositories do not by themselves prove that the complete 2026 mobile 4.2 source, Claude integration and Rhino link are available as a reproducible build under the same licence. Reuse decisions should bind the exact repository, commit and licence file to the app version.

Editorial conclusion

TopMod 3D is a notable return: it makes topology-centred manifold modelling accessible through mobile and generative interfaces while versions 4.0–4.2 expand rapidly. Its strongest value is form exploration with an editable procedural chain. Its biggest open questions are engineering validation, exact availability of modern source code and separate proof that a digital model is manufacturable.

Sources and transparency

Version numbers, dates, platform requirements and features come from Apple's developer release history. VoxelMatters served as the topic detector and workflow description, but its v3 headline conflicts with the primary version record. Texas A&M and historical GitHub mirrors support the topology history. We found no independent accuracy, CAE or manufacturability benchmark.