In spite of the widely used sophisticated software tools for mechanical design, serious difficulties are encountered in the styling phase of the design process when free-form surfaces (shortly free-forms) have to be modelled. In this paper we extend the ideas of Sachs19 pioneering 3-Draw which allowed curve sketching in 3D space in several ways: we support the creation of NURBS surfaces (not only curves), we use a semi-immersive environment centered around a table-like stereoscopic back-projection display (also know as Virtual Table or Responsive Workbench16) and we give the user an immediate preview while he sketches free-form surface.
This combination of features makes our approach unique in comparison to similar systems. Some of them only work on polyhedral models and others are restricted to indirect 3D interaction with control points. Our approach follows the Walk-Up VR concept: the user can just step in front of a Virtual Table and work on his task intuitively.