T-SubD — Tangent Subdivision Surfaces G1 Cage
Feature Request “T-SubD” G1 Surface Modeling Tool: Similar to SubD but Optimized for Industrial Design
Dear developers and community,
I would like to propose the development of a new modeling tool, or an extension to existing workflows, that functions similarly to the current SubD system but is specifically tailored for creating G1 continuous surfaces suitable for industrial design applications.
Key Requirements for the Proposed Tool:
- Behavior analogous to SubD: The tool should support G0 (position) control and editable points as primary modifiers, allowing intuitive, cage-based modeling similar to SubD.
- Output: Instead of generating SubD (polygonal subdivision) bio organic geometry, it should directly produce G1 NURBS surfaces (or a hybrid convertible to clean NURBS) for industrial design.
- Continuity per quad face: Each quadrilateral face should maintain G1 (tangent) continuity rather than G2 (curvature). This approach would enable the creation of perfect cylinders, spheres, cones, and other analytic surfaces without the typical approximation issues encountered in standard SubD-to-NURBS conversion.
- Primary use case: Industrial design and engineering workflows where precise G1 continuity is often sufficient and preferred, while avoiding the over-constrained or wavy results sometimes produced by forcing G2 continuity across complex forms.
This capability would bridge the gap between the organic freedom of SubD modeling and the precision demanded in product design, automotive, consumer electronics, and tooling applications.
For further context on the challenges with current SubD-to-NURBS workflows regarding continuity, please see the following discussions:
- SubD to NURBS G0 Continuity Problem
- SubD Challenge 3
- Bug fixing: https://mcneel.myjetbrains.com/youtrack/issue/RH-91943/BlendSrf-makes-too-complex-blends
I believe a dedicated G1-focused surface tool would significantly enhance Rhino’s suitability for professional industrial design pipelines.
Thank you for considering this suggestion. I am happy to provide additional details, examples, or participate in further discussion.
Best regards,
Alan M.