Implementing complete support for Non-Uniform Rational Basis Spline (NURBS) boundary representation geometry is a major area of active development. With NURBS, it becomes possible to import and modify geometry from other CAD and solid modeling systems without resorting to lossy format conversions, such as to polygonal mesh (BoT) geometry.
NURBS features are considered complete or are demonstrated (but not yet considered adequate) include:
- import via 3DM and STEP file formats
- robust ray tracing of valid and solid entities
- non-solid tessellation for interactive visualization
- losslessly converting implicit entities unevaluated
- solid tessellation for polygonal export (demonstrated)
- export via 3DM and STEP file formats (demonstrated)
Implementing import and robust solid ray tracing support for NURBS geometry took more than 5 years of active effort and remains a priority area of development. It supports a long-term goal of fully hybrid representation geometry where 3D data may be transparently converted between representation formats as needed.
BRL-CAD's implementation heavily leverages and extends the OpenNURBS Toolkit from Rhino3D for import and in-memory representation support. Beginning with release 7.26.0, NURBS are considered viable for production users of BRL-CAD needing import, ray tracing support, and editing via implicit CSG operations.
BRL-CAD does not yet offer complete support for NURBS. There are many features pertinent when referring to implementing NURBS that are important to some users and not others. The details regarding what NURBS functionality is started but considered incomplete include:
- explicit NURBS Boolean evaluation
- interactive surface editing
- export to polygonal mesh
- export to vector drawings
- ray tracing performance (optimization)
- converting explicit entities (e.g., BoT, NMG, EBM, Vol)
- support for (non-solid) surface NURBS
See here for more TODO topics. Help wanted.