PhD thesis

PhD thesis subject: Interactive rendering of B-Rep models on the GPU

Defended on March 20, 2014 in Toulouse (IRIT)

Link: PDF (in French)

Jury:

  • Bruno Lévy, Research Director, INRIA Nancy Grand-Est, Reviewer

  • Jean-Claude Léon, Professor, Polytechnic Institute of Grenoble, INRIA Rhône-Alpes, Reviewer

  • Marc Daniel, Professor, University of Aix-Marseille, Examiner

  • Raphaëlle Chaine, Professor, University of Lyon, Examiner

  • Loïc Barthe, Associate Professor HDR, University of Toulouse, Advisor, Examiner

  • Jean-Pierre Jessel, Professor, University of Toulouse, Thesis director

  • Mathias Paulin, Professor, University of Toulouse, Advisor, President of jury

Abstract:

Modeling software applications dedicated to Computer Aided Design (CAD) are used to design objects of all sorts, ranging from small, simple desktop lamps to entire, complex aircrafts. The B-Rep models used during this design phase allow CAD operators to define shapes in a very precise manner, and create smooth curves and surfaces meeting various design criteria, whether they are related to aesthetics, mechanical behavior, or production cost.

As modeling operations are performed in the CAD software application (eg. CATIA, for instance), models must be rendered with a fidelity and accuracy as high as possible with regards to their analytical definition as it has specifically been defined by the CAD operator. Existing modeling software applications discretize shapes as they are being edited and render polygons approximating 3D objects resulting from this discretization, usually done on a face by face basis. Gaps or "cracks" caused by this tesselation show up with this rendering method and are very annoying for the operators. We propose a method to perform crack-free, high fidelity rendering of B-Rep models, with no model preprocess and with good performance, allowing interaction even for large-scale objects. Our method can easily be integrated into existing engines based on dynamic tesselation.

Modeling sessions deal with small or medium scale object parts. Once assembled, these parts form large structures such as boats or aircrafts. These large assemblies may sometimes be interactively visualized as a whole, and once again high precision is strongly desired. Specifically, this is the case for static test applications where technicians place sensors on a virtual model called a Digital Mockup (or DMU) that is used to assess the mechanical strength of thousands of selected locations scattered throughout the model. These nail-sized sensors are then physically placed on a product entirely built and assembled in a hangar, such as an entire aircraft fuselage section. The DMU should represent as faithfully as possible the actual, physical model. For interactive rendering to take place with good frame rates and with high image quality, we rely on a trim-based rendering method with a custom, efficient, multi-resolution trim structure suitable for the rendering of large-scale models. This structure is used in conjunction with dedicated dynamic tesselation GPU routines for common types of B-Rep faces. This combination allows us to render in real-time and on current consumer hardware an entire wide-body aircraft fuselage section composed of hundreds of thousands of B-Rep faces that are dynamically tesselated and trimmed on the fly every time a rendering takes place.