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- Computation of the volume of triangulated polyhedraPublication . Gaspar, Miguel
- A Computer Tool for 3D Shape Recovery of FruitsPublication . Gaspar, Miguel; Pascoal-Faria, Paula; Amado, Sandra; Alves, NunoCharacterizing a fruit’s mechanical behavior is an important step towards reducing economic losses due to bruising. Several 3D scanning technologies allow to obtain the external geometry of a fruit, but no easily accessible tools exist for the acquisition of the geometry of internal structures such as the core. We propose a low-cost destructive method for tomographic reconstruction of a fruit from scanned slices. A method for overcoming the difficulties in registering the different images is also presented.
- Optimization of toolpath trajectories on arbitrary surfacesPublication . Gaspar, Miguel; Martins-Ferreira, N.Given an arbitrary region on the plane, modelled as a graph with a symmetry, we describe a procedure to find the best orientation for slicing, via a zigzag tool-path trajectory based curve, in order to minimize its discontinuities. We also develop some directions on how to generalize the procedure up to the level of optimizing tool-path trajectories on arbitrary surfaces rather than planar regions only.
- Rosin Based Composites for Additive ManufacturingPublication . Sousa, Dora; Biscaia, Sara; Viana, Tânia; Gaspar, Miguel Belbut; Mahendra, Vidhura; Mohan, Saeed D.; Mateus, Artur; Mitchell, GeoffreyRosins are the non-volatile exudates of pine resins with hydrophobic characteristics that are widely used as a precursor for many industrial applications. In this paper we discuss the nature, process and its applications as a matrix for a composite material for additive manufacturing. The composite material has been tailored to chemical and mechanical properties with respect to their applications.
- Sobre o cálculo dos ângulos de sopé e de convergência para veículos automóveisPublication . Martins-Ferreira, N.; Gaspar, Miguel Belbut; Mateus, Artur
- The Matlab Vectorization ParadigmPublication . Gaspar, Miguel; Martins-Ferreira, N.We give two examples of application of a vectorized programming paradigm: binary addition and cycle decomposition of directed graphs.
- Maximizing the placement of congruent polyhedrain a parallelepiped containerPublication . Gaspar, M. Belbut; Martins-Ferreira, N.Given multiple identical polyhedral objects and a parallelepiped container, how should one place the objects so that the largest number fits inside the container? This simple question is important in many applications, yet the answer is elusive. In fact, we know of no published solution for this very general formulation. Still, in many circumstances, further restrictions apply, resulting in a large number of variations requiring different algorithmic strategies. In this presentation we will further formalize the problem, present some of its many variations, and in particular one that applies to the stereolithographic rapid prototyping technology.
- Robust STL processing for extrusion-based manufacturingPublication . Gaspar, M.B.; Martins-Ferreira, N.The slicing and tool-path generation are two fundamental processing steps in rapid prototyping/rapid manufacturing (RP/RM), as well as in CAM. Nevertheless, the specific requirements of the diverse RP/RM techniques are not always addressed by existing tools for CAM. We present a set of efficient and robust algorithms for processing STL files in RP/RM.
- A procedure for computing the symmetric difference of regions defined by polygonal curvesPublication . Gaspar, Miguel Belbut; Martins-Ferreira, NelsonGiven any two regions A, B in the plane, defined by polygonal (simple, closed and oriented) curves, associated with their respective boundaries, we describe a procedure to compute the symmetric difference A ⊕ B. The output is also presented in the form of polygonal curves, where in particular the curves describing the union A ∪ B, the intersection A ∩ B, the difference A \ B, and the complement of the difference B \ A, are also obtained. This is related with the two equivalent formulas to compute the symmetric difference, namely A ⊕ B = (A ∪ B) \ (A ∩ B) = (A \ B) ∪ (B \ A).
- Innovative developments on Agile-CAD systemPublication . Gaspar, M.; Alves, N.; Martins-Ferreira, N.; Bártolo, P.Agile-CAD is a reverse engineering computer tool that allows the recovering of outer and inner 3D shapes of existing objects of revolution with constant thickness, using silhouettes computed from one or two digital views. In this context, some improved algorithms were developed in order to provide more accurate and robust tridimensional reconstruction when using a single digital image as source. Experimental results based on real images are presented, demonstrating the good performance of this computer tool.