Sparse Volumetric Deformation

Volume rendering is becoming increasingly popular as applications require realistic solid shape representations with seamless texture mapping and accurate filtering. However rendering sparse volumetric data is difficult because of the limited memory and processing capabilities of current hardware. To address these limitations, the volumetric information can be stored at progressive resolutions in the hierarchical branches of a tree structure, and sampled according to the region of interest. This means that only a partial region of the full dataset is processed, and therefore massive volumetric scenes can be rendered efficiently. The problem with this approach is that it currently only supports static scenes. This is because it is difficult to accurately deform massive amounts of volume elements and reconstruct the scene hierarchy in real-time. Another problem is that deformation operations distort the shape where more than one volume element tries to occupy the same location, and similarly gaps occur where deformation stretches the elements further than one discrete location. It is also challenging to efficiently support sophisticated deformations at hierarchical resolutions, such as character skinning or physically based animation. These types of deformation are expensive and require a control structure (for example a cage or skeleton) that maps to a set of features to accelerate the deformation process. The problems with this technique are that the varying volume hierarchy reflects different feature sizes, and manipulating the features at the original resolution is too expensive; therefore the control structure must also hierarchically capture features according to the varying volumetric resolution. This thesis investigates the area of deforming and rendering massive amounts of dynamic volumetric content. The proposed approach efficiently deforms hierarchical volume elements without introducing artifacts and supports both ray casting and rasterization renderers. This enables light transport to be modeled both accurately and efficiently with applications in the fields of real-time rendering and computer animation. Sophisticated volumetric deformation, including character animation, is also supported in real-time. This is achieved by automatically generating a control skeleton which is mapped to the varying feature resolution of the volume hierarchy. The output deformations are demonstrated in massive dynamic volumetric scenes

Implementing Compositional Analysis Using Intersection Types With Expansion Variables

AbstractA program analysis is compositional when the analysis result for a particular program fragment is obtained solely from the results for its immediate subfragments via some composition operator. This means the subfragments can be analyzed independently in any order. Many commonly used program analysis techniques (in particular, most abstract interpretations and most uses of the Hindley/Milner type system) are not compositional and require the entire text of a program for sound and complete analysis.System I is a recent type system for the pure λ-calculus with intersection types and the new technology of expansion variables. System I supports compositional analysis because it has the principal typings property and an algorithm based on the new technology of β-unification has been developed that finds these principal typings. In addition, for each natural number k, typability in the rank-k restriction of System I is decidable, so a complete and terminating analysis algorithm exists for the rank-k restriction.This paper presents new understanding that has been gained from working with multiple implementations of System I and β-unification-based analysis algorithms. The previous literature on System I presented the type system in a way that helped in proving its more important theoretical properties, but was not as easy to follow as it could be. This paper provides a presentation of many aspects of System I that should be clearer as well as a discussion of important implementation issues

Interactive image manipulation using morphological trees and spline-based skeletons

The ability to edit an image using intuitive commands and primitives is a desired feature for any image editing software. In this paper, we combine recent results in medial axes with the well-established morphological tree representations to develop an interactive image editing tool that provides global and local image manipulation using high-level primitives. We propose a new way to render interactive morphological trees using icicle plots and introduce different ways of manipulating spline-based medial axis transforms for grayscale and colored image editing. Different applications of the tool, such as watermark removal, image deformation, dataset augmentation for machine learning, artistic illumination manipulation, image rearrangement, and clothing design, are described and showcased on examples

How functional programming mattered

In 1989 when functional programming was still considered a niche topic, Hughes wrote a visionary paper arguing convincingly ‘why functional programming matters’. More than two decades have passed. Has functional programming really mattered? Our answer is a resounding ‘Yes!’. Functional programming is now at the forefront of a new generation of programming technologies, and enjoying increasing popularity and influence. In this paper, we review the impact of functional programming, focusing on how it has changed the way we may construct programs, the way we may verify programs, and fundamentally the way we may think about programs

Pushing the envelope for estimating poses and actions via full 3D reconstruction

Estimating poses and actions of human bodies and hands is an important task in the computer vision community due to its vast applications, including human computer interaction, virtual reality and augmented reality, medical image analysis. Challenges: There are many in-the-wild challenges in this task (see chapter 1). Among them, in this thesis, we focused on two challenges which could be relieved by incorporating the 3D geometry: (1) inherent 2D-to-3D ambiguity driven by the non-linear 2D projection process when capturing 3D objects. (2) lack of sufficient and quality annotated datasets due to the high-dimensionality of subjects' attribute space and inherent difficulty in annotating 3D coordinate values. Contributions: We first tried to jointly tackle the 2D-to-3D ambiguity and insufficient data issues by (1) explicitly reconstructing 2.5D and 3D samples and use them as new training data to train a pose estimator. Next, we tried to (2) encode 3D geometry in the training process of the action recognizer to reduce the 2D-to-3D ambiguity. In appendix, we proposed a (3) new hand pose synthetic dataset that can be used for more complete attribute changes and multi-modal experiments in the future. Experiments: Throughout experiments, we found interesting facts: (1) 2.5D depth map reconstruction and data augmentation can improve the accuracy of the depth-based hand pose estimation algorithm, (2) 3D mesh reconstruction can be used to generate a new RGB data and it improves the accuracy of RGB-based dense hand pose estimation algorithm, (3) 3D geometry from 3D poses and scene layouts could be successfully utilized to reduce the 2D-to-3D ambiguity in the action recognition problem.Open Acces

Matisse : Painting 2D regions for Modeling Free-Form Shapes

International audienceThis paper presents "Matisse", an interactive modeling system aimed at providing the public with a very easy way to design free-form 3D shapes. The user progressively creates a model by painting 2D regions of arbitrary topology while freely changing the view-point and zoom factor. Each region is converted into a 3D shape, using a variant of implicit modeling that fits convolution surfaces to regions with no need of any optimization step. We use intuitive, automatic ways of inferring the thickness and position in depth of each implicit primitive, enabling the user to concentrate only on shape design. When he or she paints partly on top of an existing primitive, the shapes are blended in a local region around the intersection, avoiding some of the well known unwanted blending artifacts of implicit surfaces. The locality of the blend depends on the size of smallest feature, enabling the user to enhance large, smooth primitives with smaller details without blurring the latter away. As the results show, our system enables any unprepared user to create 3D geometry in a very intuitive way