Portuguese Meeting on Computer Graphics 2011 - SIACG 2011

Permanent URI for this collection

https://diglib.eg.org/handle/10.2312/2633063

Browse

Browsing Portuguese Meeting on Computer Graphics 2011 - SIACG 2011 by Subject "Computational Geometry and Object Modeling"

Now showing 1 - 5 of 5
  • No Thumbnail Available
    Item
    GPU Collision Detection in Conformal Geometric Space
    (The Eurographics Association, 2021) Roa, Eduardo; Theoktisto, Víctor; Fairén, Marta; Navazo, Isabel; Silva, F. and Gutierrez, D. and Rodríguez, J. and Figueiredo, M.
    We derive a conformal algebra treatment unifying all types of collisions among points, vectors, areas (defined by bivectors and trivectors) and 3D solid objects (defined by trivectors and quadvectors), based in a reformulation of collision queries from R3 to conformal R4,1 space. The algebraic formulation in this 5D space is then implemented in GPU to allow faster parallel computation queries. Results show expected orders of magnitude improvements computing collisions among known mesh models, allowing interactive rates without using optimizations and bounding volume hierarchies.
  • No Thumbnail Available
    Item
    A Moving Least Squares Method for Implant Model Deformation in Computer Aided Orthopedic Surgery for Fractures of Lower Extremities
    (The Eurographics Association, 2021) Ramírez, Esmitt; Coto, Ernesto; Silva, F. and Gutierrez, D. and Rodríguez, J. and Figueiredo, M.
    Preoperative planning is an essential step before performing any surgical procedure. Computer Aided Orthopedic Surgery (CAOS) systems are extensively used for the planning of surgeries for fractures of lower extremities. These systems are input an X-Ray image and the planning can be digitally overlaid onto the image. The planning includes reassembling the fractured bone and possibly adding implants to reduce the fracture. In many cases, the implant does not fit perfectly in the patient's anatomy and it must be bended to adjust the implant to the bone. This paper presents a new method for the deformation of implants in CAOS systems, based on the Moving Least Squares (MLS) method for 2D images. Several improvements over the original MLS method are introduced to achieve visual results similar to the real procedure and make the deformation process easier and simpler for the surgeon. The improvements are explained in detail and all parameter values are provided. Over 100 clinical surgeries have been already planned successfully using a CAOS system that employs the proposed technique.
  • No Thumbnail Available
    Item
    Procedural Modeling of Suspension Bridges
    (The Eurographics Association, 2021) Patow, Gustavo; Silva, F. and Gutierrez, D. and Rodríguez, J. and Figueiredo, M.
    In this paper we introduce a method for designing a class of engineering structures, namely suspension bridges. These bridges are ubiquitous in the industrialized countries, often appearing in known city landscapes, yet they are complex enough that hand-based modeling is tedious and time consuming. We present a method that finds the right proportions for such a structure through an optimization method that tries to distribute the tower positions while maintaining cable width to be a finite number. By simultaneously optimizing the span and sag of the cables of a bridge, we optimize the geometry and soundness of the structure. We present the details of our technique together with examples illustrating its use, including comparisons with real structures.
  • No Thumbnail Available
    Item
    Real-Time Modelling and Rendering of Sprayed Concrete
    (The Eurographics Association, 2021) Vélez, G.; Matey, L.; Amundarain, A.; Ordás, F.; Marín, J.A.; Silva, F. and Gutierrez, D. and Rodríguez, J. and Figueiredo, M.
    This paper presents a new real-time method to model and render how sprayed concrete is spread on a surface. The method not only models and renders deposits sprayed from any angle, any distance and with any concrete flow, but it is also able to compute the amount of deposited volume taking into account the percentage of material that rebounds. The proposed method has been developed for a real-time training simulator for concrete spraying machinery, where most of the algorithm is parallelised and computed in the GPU, leaving the CPU free for other computations. In this research, the method has been validated for its use on plain surfaces and tunnel walls, but it can be extended to other types of surfaces.
  • No Thumbnail Available
    Item
    A Simple Surface Tracking Method for Physically-Based 3D Water Simulations
    (The Eurographics Association, 2021) Amador, G.; Gomes, A.; Silva, F. and Gutierrez, D. and Rodríguez, J. and Figueiredo, M.
    Water simulation, and more generically fluid simulation, is an important research topic in computer graphics. In 3D Eulerian Navier-Stokes-based water simulations, surface tracking and rendering are two delicate problems. The existing solutions to these problems (i.e., implicit surfaces-based approaches, height-fields, ray-tracing), are either to computationally intensive for real-time scenarios, or present bulge water surfaces (i.e., blobby water surfaces). In this paper, we propose a novel tracking algorithm for rendering water surfaces. Instead of tracking the flow of water using either level sets or height-fields, each cell of an 3D grid density value is directly measured in order to determine if it is either water, air, or water-air contact surface. The information in each cell is later used for the water surface splat rendering, using OpenGL vertex buffer objects.