Carlos A. Dietrich

What went wrong? A survey of problems in game development

Despite its growth and profitability, many reports about game projects show that their production is not a simple task, but one beset by common problems and still distant from having a healthy and synergetic work process. The goal of this article is to survey the problems in the development process of electronic games, which are mainly collected from game postmortems, by exploring their similarities and differences to well-known problems in traditional information systems.

Edge Transformations for Improving Mesh Quality of Marching Cubes

Marching Cubes is a popular choice for isosurface extraction from regular grids due to its simplicity, robustness, and efficiency. One of the key shortcomings of this approach is the quality of the resulting meshes, which tend to have many poorly shaped and degenerate triangles. This issue is often addressed through post processing operations such as smoothing. As we demonstrate in experiments with several datasets, while these improve the mesh, they do not remove all degeneracies, and incur an increased and unbounded error between the resulting mesh and the original isosurface. Rather than modifying the resulting mesh, we propose a method to modify the grid on which Marching Cubes operates. This modification greatly increases the quality of the extracted mesh. In our experiments, our method did not create a single degenerate triangle, unlike any other method we experimented with. Our method incurs minimal computational overhead, requiring at most twice the execution time of the original Marching Cubes algorithm in our experiments. Most importantly, it can be readily integrated in existing Marching Cubes implementations, and is orthogonal to many Marching Cubes enhancements (particularly, performance enhancements such as out-of-core and acceleration structures).

Houston, we have a problem...: a survey of actual problems in computer games development

This paper presents a survey of problems found in the development process of electronic games. These problems were collected mainly from game postmortems and specialized litterature on game development, allowing a comparison with respect to well-known problems in the traditional software industry.

On determining a signature for skeletal maturity

We present a computational framework for semi-automated assessment of skeletal age based on a multi-scale image analysis approach. Through 2D digital X-ray images of the left hand, maturity indicators are searched by means of a two-step process: the user interactively indicates a point inside the middle finger, and the computational method analyzes the image intensity profile along this line, searching for physiological signatures related to different epiphyseal events (ossification, cartilage stage, early fusion and complete fusion). A scale-space approach is used to select the best scale to enhance the edges between the bones and soft tissues. Initial results indicate that this approach could be useful to facilitate the analysis of growth disorders in pediatrics.

Erasing, digging and clipping in volumetric datasets with one or two hands

Visualization of volumetric datasets is common in many fields and has been an active area of research in the past two decades. In spite of developments in volume visualization techniques, interacting with large datasets still demands research efforts due to perceptual and performance issues. The support of graphics hardware for texture-based visualization allows efficient implementation of rendering techniques that can be combined with interactive sculpting tools to enable interactive inspection of 3D datasets. In this paper we report the development of three 3D interactive tools, eraser, digger and clipper, which specify regions within the volume to be discarded from rendering. Sculpting is accomplished by running special fragment programs that discard fragments based on geometric predicates. The interaction techniques we proposed were implemented using the virtual hand metaphor. The tools were evaluated by comparing the use of a 3D mouse against a conventional wheel-mouse for guiding volume and tools manipulation. Two-handed input was tested with both types of mouse and the results obtained indicate a preference for a combination of 2D and 3D mouse.

Real-time interactive visualization and manipulation of the volumetric data using GPU-based methods

This work presents a set of tools developed to provide 3D visualization and interaction with large volumetric data that relies on recent programmable capabilities of consumer-level graphics cards. We are exploiting the programmable control of calculations performed by the graphics hardware for generating the appearance of each pixel on the screen to develop real-time, interactive volume manipulation tools. These tools allow real-time modification of visualization parameters, such as color and opacity classification or the selection of a volume of interest, extending the benefit of hardware acceleration beyond display, namely for computation of voxel visibility. Three interactive tools are proposed: a cutting tool that allows the selection of a convex volume of interest, an eraser-like tool to eliminate non-relevant parts of the image and a digger-like tool that allows the user to eliminate layers of a 3D image. To interactively apply the proposed tools on a volume, we are making use of some so known user interaction techniques, as the ones used in 2D painting systems. Our strategy is to minimize the user entrainment efforts involved in the tools learning. Finally, we illustrate the potential application of the conceived tools for preoperative planning of liver surgery and for liver vascular anatomy study. Preliminary results concerning the system performance and the images quality and resolution are presented and discussed.

Marching Cubes without Skinny Triangles

Most computational codes that use irregular grids depend on the single worst triangles quality: skinny triangles can lead to bad performance and numerical instabilities. Marching cubes (MC) is the standard isosurface grid generation algorithm, and, whereas most triangles it generates are good, it almost always generates some bad triangles. Here, we show how simple changes to MC can lead to a drastically reduced number of degenerate triangles, making it a more practical choice for isosurface grid generation.

Edge Groups: An Approach to Understanding the Mesh Quality of Marching Methods

Marching cubes is the most popular isosurface extraction algorithm due to its simplicity, efficiency and robustness. It has been widely studied, improved, and extended. While much early work was concerned with efficiency and correctness issues, lately there has been a push to improve the quality of marching cubes meshes so that they can be used in computational codes. In this work we present a new classification of MC cases that we call edge groups, which helps elucidate the issues that impact the triangle quality of the meshes that the method generates. This formulation allows a more systematic way to bound the triangle quality, and is general enough to extend to other polyhedral cell shapes used in other polygonization algorithms. Using this analysis, we also discuss ways to improve the quality of the resulting triangle mesh, including some that require only minor modifications of the original algorithm.

Efficient and High Quality Contouring of Isosurfaces on Uniform Grids

The interactive polygonization of isosurfaces has become possible with the mapping of the Marching Cubes (MC) and Marching Tetrahedra (MT) algorithms to GPUs. Such mapping is not as straightforward in cases that the algorithm generate meshes closer to the isosurface or result in better polygon shapes, since they often require complex computations for the vertex positioning of the polygons or even do not have table-driven implementations. In this paper, we revisit Dual Contouring (DC) and Macet algorithms and propose, respectively: (i) a novel parallel efficient version on uniform grids and (ii) novel GPU modules which extend the original MC. Our DC algorithm is table-driven and positions the vertices in a particle-based fashion, which is then used to map into a GPU implementation. In addition, we enumerate the current ways to implement efficient contouring algorithms on the GPUs as orthogonal features, and present the tradeoff of each approach. We validate the efficiency of our algorithms with its comparison to interactive versions of MC algorithms.

Baseball4D: A tool for baseball game reconstruction & visualization

While many sports use statistics and video to analyze and improve game play, baseball has led the charge throughout its history. With the advent of new technologies that allow all players and the ball to be tracked across the entire field, it is now possible to bring this understanding to another level. From discrete positions across time, we present techniques to reconstruct entire baseball games and visually explore each play. This provides opportunities to not only derive new metrics for the game, but also allow us to investigate existing measures with targeted visualizations. In addition, our techniques allow users to filter on demand so specific situations can be analyzed both in general and according to those situations. We show that gameplay can be accurately reconstructed from the raw position data and discuss how visualization and statistical methods can combine to better inform baseball analyses.