# Key Technical Discussions from #hplusroadmap

• A user described developing a pneumatic stepper motor for RepRap 3D printers, referencing a Japanese research project that achieved a 9mm diameter motor with 420 steps per revolution using a "wobble motor" design that could be easily 3D printed.

• Participants shared open-source Finite Element Method (FEM) resources including ElmerFEM and CAELinux for mechanical component analysis and design validation.

• The conversation highlighted significant technical challenges in HeeksCAD regarding memory management and shape tracking, specifically how the software fails to properly track surfaces, faces, edges, and points after converting them to shapes.

• Users discussed the implementation of feature trees in CAD software, explaining how these structures maintain relationships between base shapes and dependent operations to enable parametric modifications throughout a model.

• There was detailed technical discussion about NURBS curves (Non-Uniform Rational B-Splines) as mathematical models for representing curves and surfaces, with clarification that Bezier curves are a specific class of NURBS using cubic polynomials.

• Developers shared their work integrating pythonOCC (Python bindings for OpenCascade) with graphical interfaces, including specific challenges with mouse selection, shape manipulation, and wxWidgets programming for toolbar implementation.

• The group debated approaches to implementing undo functionality in CAD software, with one participant advocating for rebuilding shapes from scratch based on stored operations rather than using traditional undo/redo queues.