João F Oliveira | University College London (original) (raw)

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Papers by João F Oliveira

This paper presents the current state of development of a generation and performance evaluation t... more This paper presents the current state of development of a generation and performance evaluation tool to assist building practitioners in the early stages of deep renovation of buildings. This includes the tool workflow and its modules, such as the generative design method, the building performance evaluation mechanism, and the optimization procedure that improves the building geometry and construction system, and sizes the energy systems (HVAC and renewable energy production). The tool is currently able to use a wide variety of EnergyPlus objects, allowing for various template and detailed HVAC, DHW, and thermal and electrical energy production systems and components, as well as numerous internal gains types, construction elements and energy saving controls, to be accounted for and simulated in the generated buildings. Some applications examples are presented to demonstrate the tool capabilities. Lastly, some conclusions are made. Eugénio Rodrigues, Marco S. Fernandes, Adélio R. Gas...

International Journal of Virtual Reality, 2012

Point cloud models are a common shape representation for several reasons. Three-dimensional scann... more Point cloud models are a common shape representation for several reasons. Three-dimensional scanning devices are widely used nowadays and points are an attractive primitive for rendering complex geometry. Nevertheless, there is not much literature on collision detection for point cloud models. This paper presents a novel collision detection algorithm for large point cloud models using voxels, octrees and bounding spheres hierarchies (BSH). The scene graph is divided in voxels. The objects of each voxel are organized intoan octree. Due to the high number of points in the scene, each non-empty cell of the octree is organized in a bounding sphere hierarchy, based on an R-tree hierarchy like structure. The BSH hierarchies are used to group neighboring points and filter out very quickly parts of objects that do not interact with other models. Points derived from laser scanned data typically are not segmented and can have arbitrary spatial resolution thus introducing computational and mod...

With the advent of whole body, 3D electro-optical scanners, a new range of applications are emerg... more With the advent of whole body, 3D electro-optical scanners, a new range of applications are emerging that exploit the availability of personalised, realistic human models. However, realistic rendering of such models usually entails a large number of polygons which can be unacceptable in many applications. We present a framework that exploits the approximate cylindrical and spherical symmetry of human body parts to create light-weight representations that retain the overall dimension of body parts, even at very low polygon counts. __________________________________________________________________________________________

D electro-optical scanners provide high resolution data which are interesting for many applicatio... more D electro-optical scanners provide high resolution data which are interesting for many applications. Often before these models can be used, surface simplification techniques need to be applied to create the right size for the intended application. These techniques can ensure overall good quality in lower level of detail models, but often at the price of loosing the initial local fidelity of the higher resolution scan. This paper presents a solution for retaining high fidelity through a non-linear simplification process, and presents new constraints that allow to achieve this.The presented system can preserve similar user selected region sets and automatically create levels of detail with the same preservation/degradation characteristics in different scans.

As main memory continues to increase in size, larger 3D models can be loaded into memory. As thes... more As main memory continues to increase in size, larger 3D models can be loaded into memory. As these models grow in size, in spite of continuing improvements in graphics pipelines, they continue to present new challenges for the rendering hardware. Solutions for decreasing the load on graphics hardware, such as level of detail and vertex hierarchies, work well if enough main memory is present for the model at hand. We present a new data structure (RenderArray) that allows load balancing with little memory overhead. The RenderArray allows fast display of any size model that fits in main memory, by only rendering the parts of the model that are near to the foremost intersection point of the line of sight with the model. An octree is used for this calculation, but in order to accommodate models near the main memory limit, without causing the system to page, we introduce a novel memory-friendly way of building a compact octree that does not store triangles at leaf nodes. The RenderArray i...

Spatial reasoning of vascular structures in organs such as the liver is an imperative task perfor... more Spatial reasoning of vascular structures in organs such as the liver is an imperative task performed preoperatively in resection planning when minimising risks of bleeding in a procedure and intra-operatively during surgery. Accurate automatic 3D reconstruction of surfaces from computerized tomography (CT) contours is complex or impossible without user intervention. Often the gap between scan slices is large enough to make contour correspondence between adjacent slices hard to establish and branching difficult to determine. Freely available open source libraries such as the image guided surgery toolkit and the visualization toolkit (IGSTK and VTK respectively) provide building blocks that enable one to speed up the development time whilst allowing one to focus on new algorithms that might help the user. In this paper we present a new automatic solution for visualization/spatial reasoning of vascular networks within the liver that uses two separate 3D reconstruction approaches respec...

Journal of Biomedical Engineering and Medical Imaging, 2017

Proceedings of the ACM symposium on Virtual reality software and technology - VRST '06, 2006

Videometrics, Range Imaging, and Applications X, 2009

Advances in both terrestrial laser scanning (TLS) hardware and photogrammetric solutions combined... more Advances in both terrestrial laser scanning (TLS) hardware and photogrammetric solutions combined are creating increasingly more precise and rich 3D coloured data. In this article we show how Computer Graphics and Visualization techniques have played an important role in managing, modelling, and fusing data in an increasing myriad of applications such as environmental surveying, structure analysis, architecture and archaeology. Specifically we describe the typical modelling steps involved in the creation of a range of digital documents provided by the 3D digitization company Artescan to customers. In addition, we also address and discuss some limitations of existing software solutions and outline potential future research opportunities.

Image-based rendering techniques take the approach of rendering new images based on existing ones... more Image-based rendering techniques take the approach of rendering new images based on existing ones, effectively separating the rendering complexity from the geometric complexity of the scene they represent. With the increasing complexity of scenes currently created, these techniques have gained renewed interest. This paper presents a multi-cellular IBR approach, which uses orthographic rather than perspective projected pre-computed images. Specifically we extend our single cell orthographically projected IBR approach to a multi-cell system, and show how the pixel error can be further reduced with the use of smaller and more numerous cells.

In the last few years there has been a significant evolution in the mobile devices hardware capab... more In the last few years there has been a significant evolution in the mobile devices hardware capabilities, this evolution is very important as it allows for more complex applications and services to be developed for this type of devices. In this paper we describe the concepts and key issues that arise when developing an Augmented Reality system in a localization application for smartphones in general. WorldPlus presents solutions and implements these concepts using the Android smartphone as an example. In addition, WorldPlus allows programmers to develop their own content providers for both an online and an offline mode.

The Photogrammetric Record

The standard starting point for the extraction of information from human face image data is the d... more The standard starting point for the extraction of information from human face image data is the detection of key anatomical landmarks, which is a vital initial stage for several applications, such as face recognition, facial analysis and synthesis. Locating facial landmarks in images is an important task in image processing and detecting it automatically still remains challenging. The appearance of facial landmarks may vary tremendously due to facial variations. Detecting and extracting landmarks from raw face data is usually done manually by trained and experienced scientists or clinicians, and the landmarking is a laborious process. Hence, we aim to develop methods to automate as much as possible the process of landmarking facial features. In this paper, we present and discuss our new automatic landmarking method on face data using 2.5-dimensional (2.5D) range images. We applied the Scale-invariant Feature Transform (SIFT) method to extract feature vectors and the Otsu’s method to...