Ten questions that arose in designing the Djinn API for solid modelling

Djinn is an API for solid modelling which is defined in the language of point-sets and is thus independent of any particular modelling data-structure (e.g. boundary representations or CSG trees). In designing this API, several significant and interesting questions have arisen, including: the basic feasibility of the approach; deciding how to support cellular models; providing facilities for navigation without traditional data-structures; addressing the problems of 'tweaks' and blends; ensuring that labels are preserved under geometric operations; permitting regions in which changes to a model have taken place to be identified; coping with approximate models; deciding whether to support variational models; keeping sweeps and transforms within a reasonable domain; and providing facilities to handle the many types of parametric surface. These questions are not all fully answered, but progress continues towards a published interface and C++ language binding.