Accelerated, Collaborative & Extended BlobTree Modelling (PhD Test Talk)

BlobTree modelling has been used in several solid modelling packages to rapidly prototype models by making use of boolean and sketch-based modelling. Using these two techniques, a user can quickly create complex models as combinations of simple primitives and sketched objects. Because the BlobTree is based on continuous field-values, it offers a lot of possibilities to create and control smooth transitions between surfaces, something more complicated in other modelling approaches. In addition, the data required to describe a BlobTree is very compact. Despite these advantages, the BlobTree has not yet been integrated into state of the art industrial workflows to create models. This thesis identifies some shortcomings of the BlobTree, presents potential solutions to those problems and demonstrates an application that makes use of the BlobTree’s compact representation. A main criticism is that the evaluation of a large BlobTree can be quite expensive, and, therefore, many applications are limited in the complexity of models that can be created interactively. This work presents an alternative way of traversing a BlobTree that lowers the time to calculate field-values by at least an order of magnitude. As a result, the limit of model complexity is raised for interactive modelling applications. In some domains, certain models need more than one designer or engineer to be created. Often, several iterations of a model are shared between multiple participants until it is finalized. Because the description of a BlobTree is very compact, it can be synchronized efficiently in a collaborative modelling environment. This work presents CollabBlob, an approach to collaborative modelling based on the BlobTree. CollabBlob is lock-free, and provides interactive feedback for all the participants, which helps with a fast iteration in the modelling process. In order to extend the range of models that can be created within CollabBlob, two areas of BlobTree modelling are improved in the context of this thesis. CAD modelling often makes use of a feature called filleting to add additional surface features, which could be caused by a manufacturing process. Filleting in general creates smooth transitions between surfaces, something that the BlobTree can do with less mathematical complexity than approaches needed in Constructive Solid Geometry (CSG), in the case of fillets between primitives. However, little research has been done on the construction of fillets between surfaces of a single BlobTree primitive. This work outlines Angle-Based Filleting and the Surface Fillet Curve, two solutions to improve the specification of fillets in the BlobTree. Sketch-based implicit modelling generates 3D shapes from 2D sketches by sampling the drawn shape and using the samples to create the implicit field via variational interpolation. Additional samples inside and outside the sketched shape are needed to generate a field compatible with BlobTree modelling and state of the art approaches use offset curves of the sketch to generate these samples. The approach presented in this work reduces the number of sample points, thus accelerating the interpolation time and improving the resulting implicit field.