  Shape modeling research in Computer Graphics has been an active area for
decades. The ability to create and edit complex 3D shapes has been of key
importance in Computer-Aided Design, Animation, Architecture, and
Entertainment. With the growing popularity of Virtual and Augmented Reality,
new applications and tools have been developed for artistic content creation;
real-time interactive shape modeling has become increasingly important for a
continuum of virtual and augmented reality environments (eXtended Reality
(XR)). Shape modeling in XR opens new possibilities for intuitive design and
shape modeling in an accessible way. Artificial Intelligence (AI) approaches
generating shape information from text prompts are set to change how artists
create and edit 3D models. There has been a substantial body of research on
interactive 3D shape modeling. However, there is no recent extensive review of
the existing techniques and what AI shape generation means for shape modeling
in interactive XR environments. In this state-of-the-art paper, we fill this
research gap in the literature by surveying free-form shape modeling work in
XR, with a focus on sculpting and 3D sketching, the most intuitive forms of
free-form shape modeling. We classify and discuss these works across five
dimensions: contribution of the articles, domain setting, interaction tool,
auto-completion, and collaborative designing. The paper concludes by discussing
the disconnect between interactive 3D sculpting and sketching and how this will
likely evolve with the prevalence of AI shape-generation tools in the future.
