Ignacio Martín

Frame-to-frame coherent animation with two-pass radiosity

This paper proposes an efficient method for the production of high quality radiosity solutions which uses an a priori knowledge of the dynamic properties of the scene to exploit temporal coherence. The method is based on a two-pass strategy that provides user-control on the final frame quality. In the first pass, it computes a coarse global solution of the radiosities along a time interval and then, in the second pass, it performs a frame-to-frame incremental gathering step using hardware graphic accelerators. Computing cost is thus reduced because the method takes advantage of frame-to-frame coherence by identifying the changes produced by dynamic objects and by decoupling them from computations that remain unchanged. The input data is a dynamic model of the environment through a period of time corresponding to the same camera recording. The method proceeds by incrementally updating two data structures: a space-time hierarchical radiosity solution for a given interval of time and a hierarchical tree of textures representing the space-time final illumination of the visible surfaces. These data structures are computed for a given viewpoint, either static or dynamic. The main contribution of this work is the efficient construction of the texture tree by identifying the changes produced by dynamic objects and by only recomputing these changes.

A GPU-driven algorithm for accurate interactive reflections on curved objects

We present a GPU-driven method for the fast computation of specular reflections on curved objects. For every reflector of the scene, our method computes a virtual object for every other object reflected in it. This virtual reflected object is then rendered and blended with the scene. For each vertex of each virtual object, a reflection point is found on the reflectors surface. This point is used to find the reflected virtual vertex, enabling the reflected virtual scene to be rendered. Our method renders the 3D points and normals of the reflector into textures, and uses a local search in a fragment program on the GPU to find the reflection points. By reorganizing the data and the computation in this manner, and correctly treating special cases, we make excellent use of the parallelism and stream-processing power of the GPU. In our results we show that, with our method, we can display high-quality reflections of nearby objects interactively.

Radiosity for dynamic environments

In this paper we present a radiosity algorithm for dynamic scenes with a high level of frame-to-frame coherence. The algorithm is restricted to dynamic environments, where the objects movement is known a priori and the viewpoint is static. Each image is computed as the sum of two images: the base-level image, computed in a pre-process, and the frame-level image computed incrementally at each frame. The computation of the images is based on an importance-driven heuristic approach. The results of the implementation are analysed and discussed.

A Two-Pass Hardware-Based Method for Hierarchical Radiosity

Finite elements methods for radiosity are aimed at computing global illumination solutions efficiently. However these methods are not suitable for obtaining high quality images due to the lack of error control. Two‐pass methods allow to achieve that level of quality computing illumination at each pixel and thus introducing a high computing overhead. We present a two‐pass method for radiosity that allows to produce high quality images avoiding most of the per‐pixel computations. The method computes a coarse hierarchical radiosity solution and then performs a second pass using current graphics hardware accelerators to generate illumination as high definition textures.

Evaluation of self-combustion risk in tire derived aggregate fills

Lightweight tire derived aggregate (TDA) fills are a proven recycling outlet for waste tires, requiring relatively low cost waste processing and being competitively priced against other lightweight fill alternatives. However its value has been marred as several TDA fills have self-combusted during the early applications of this technique. An empirical review of these cases led to prescriptive guidelines from the ASTM aimed at avoiding this problem. This approach has been successful in avoiding further incidents of self-combustion. However, at present there remains no rational method available to quantify self-combustion risk in TDA fills. This means that it is not clear which aspects of the ASTM guidelines are essential and which are accessory. This hinders the practical use of TDA fills despite their inherent advantages as lightweight fill. Here a quantitative approach to self-combustion risk evaluation is developed and illustrated with a parametric analysis of an embankment case. This is later particularized to model a reported field self-combustion case. The approach is based on the available experimental observations and incorporates well-tested methodological (ISO corrosion evaluation) and theoretical tools (finite element analysis of coupled heat and mass flow). The results obtained offer clear insights into the critical aspects of the problem, allowing already some meaningful recommendations for guideline revision.

Fast inverse reflector design (FIRD)

This paper presents a new inverse reflector design method using a GPU‐based computation of outgoing light distribution from reflectors. We propose a fast method to obtain the outgoing light distribution of a parametrized reflector, and then compare it with the desired illumination. The new method works completely in the GPU. We trace millions of rays using a hierarchical height‐field representation of the reflector. Multiple reflections are taken into account. The parameters that define the reflector shape are optimized in an iterative procedure in order for the resulting light distribution to be as close as possible to the desired, user‐provided one. We show that our method can calculate reflector lighting at least one order of magnitude faster than previous methods, even with millions of rays, complex geometries and light sources.

Compression and Importance Sampling of Near‐Field Light Sources

This paper presents a method for compressing measured datasets of the near‐field emission of physical light sources (represented by raysets). We create a mesh on the bounding surface of the light source that stores illumination information. The mesh is augmented with information about directional distribution and energy density. We have developed a new approach to smoothly generate random samples on the illumination distribution represented by the mesh, and to efficiently handle importance sampling of points and directions. We will show that our representation can compress a 10 million particle rayset into a mesh of a few hundred triangles. We also show that the error of this representation is low, even for very close objects.

High Quality Final Gathering for Hierarchical Monte Carlo Radiosity for General Environments

Aiming at rendering high quality images robustly for general environments with simple algorithms, we use a two-pass method that accounts for the global illumination. In this paper we present the integration of a new gathering procedure in the rendering pass, that uses the approximate results obtained by a particle tracing method, an extension of the Hierarchical Monte Carlo Radiosity (HMCR) algorithm. Results from our implementation demonstrate the efficient generation of high quality images using the technique presented herein.