Synchronized-tracing of implicit surfaces

Implicit surfaces are known for their ability to represent smooth objects of arbitrary topology thanks to hierarchical combinations of primitives using a structure called a blobtree. We present a new tile-based rendering pipeline well suited for modeling scenarios, i.e., no preprocessing is required when primitive parameters are updated. When using approximate signed distance fields, we rely on compact, smooth CSG operators - extended from standard bounded operators - to compute a tight volume of interest for all primitives of the blobtree. The pipeline relies on a low-resolution A-buffer storing the primitives of interest of a given screen tile. The A-buffer is then used during ray processing to synchronize threads within a subfrustum. This allows coherent field evaluation within workgroups. We use a sparse bottom-up tree traversal to prune the blobtree on-the-fly which allows us to decorrelate field evaluation complexity from the full blobtree size. The ray processing itself is done using the sphere-tracing algorithm. The pipeline scales well to surfaces consisting of thousands of primitives

N-ary implicit blends with topology control

International audienceConstructive implicit surfaces are attractive for modeling and animation because they seamlessly handle shapes with complex and dynamic topology. However, the way they merge shapes is difficult to control. This paper introduces a solution: an improved blend operator that provides control over how topology changes are handled. It is based on a correction applied to the standard blending operator: the sum. Building on summation preserves the n-ary nature of the blend, providing the simplicity of arbitrary (e.g. flat) construction trees and segmentation invariance. The correction is based on projection to a reference case in the variation-space defined by the field and the norm of its gradient. It provides a single parameter, allowing for tuning behavior to achieve effects ranging from avoiding topological combination, through merging only during overlap, to merging at a distance. Dynamic adjustment of the parameter allows for context-dependent effects. Applications range from skeleton-based modeling, where shapes keep the topology of their skeleton, to objects that change topology during animation, with controllable merging. We illustrate the latter with Manga-style hair, where merging depends on the angle between hair wisps

Surfaces Implicites Homothétiques

National audienceNous introduisons un nouveau type de surface implicite à squelette, étendant le modèle des surfaces de convolution. La principale propriété de ces nouvelles surfaces est d'être invariantes par homothétie, ce qui rend leur utilisation bien plus intuitive : les mélanges ont la même allure à toutes les échelles, et nous pouvons contrôler plus précisément l'épaisseur du volume englobé

Transparent rendering and slicing of integral surfaces using per-primitive interval arithmetic

International audienceWe present a method for efficient incorporation of integral surfaces within existing robust processing methods such as interval arithmetic and segment-tracing. We based our approach on high-level knowledge of the field function of the primitives. We show application to slicing and transparent rendering of integral surfaces based on interval arithmetic

A brick in the wall: Staggered orientable infills for additive manufacturing

International audienceAdditive manufacturing is typically conducted in a layer-by-layer fashion. A key step of the process is to define, within each planar layer, the trajectories along which material is deposited to form the final shape. The direction of these trajectories triggers an anisotropy in the fabricated parts, which directly affects their properties, from their mechanical behavior to their appearance. Controlling this anisotropy paves the way to novel applications, from stronger parts to controlled deformations and surface patterning.This work introduces a method to generate trajectories that precisely follow an input direction field while simultaneously avoiding intra- and inter-layer defects. Our method results in spatially coherent trajectories - all follow the specified direction field throughout the layers - while providing precise control over their inter-layer arrangement. This allows us to generate a staggered layout of trajectories across layers, preventing unavoidable tiny gaps from forming tunnel-shaped voids throughout a part volume.Our approach is simple, robust, easy to implement, and scales linearly with the input volume. It builds upon recent results in procedural generation of oscillating patterns, generating a signal in the 3D domain that oscillates with a frequency matching the deposition beads width while following the input direction field. Trajectories are extracted with a process akin to a marching square

SCALe-invariant Integral Surfaces

International audienceExtraction of skeletons from solid shapes has attracted quite a lot of attention, but less attention was paid so far to the reverse operation: generating smooth surfaces from skeletons and local radius information. Convolution surfaces, i.e. implicit surfaces generated by integrating a smoothing kernel along a skeleton, were developed to do so. However, they failed to reconstruct prescribed radii and were unable to model large shapes with fine details. This work introduces SCALe-invariant Integral Surfaces (SCALIS), a new paradigm for implicit modeling from skeleton graphs. Similarly to convolution surfaces, our new surfaces still smoothly blend when field contributions from new skeleton parts are added. However, in contrast with convolution surfaces, blending properties are scale invariant. This brings three major benefits: the radius of the surface around a skeleton can be explicitly controlled, shapes generated in blending regions are self-similar regardless of the scale of the model, and thin shape components are not excessively smoothed out when blended into larger ones

Procedural Phasor Noise

International audienceProcedural pattern synthesis is a fundamental tool of Computer Graphics, ubiquitous in games and special effects. By calling a single procedure in every pixel – or voxel – large quantities of details are generated at low cost, enhancing textures, producing complex structures within and along surfaces. Such procedures are typically implemented as pixel shaders. We propose a novel procedural pattern synthesis technique that exhibits desirable properties for modeling highly contrasted patterns, that are especially well suited to produce surface and microstructure details. In particular, our synthesizer affords for a precise control over the profile, orientation and distribution of the produced stochastic patterns, while allowing to grade all these parameters spatially. Our technique defines a stochastic smooth phase field – a phasor noise –that is then fed into a periodic function (e.g. a sine wave), producing an oscillating field with prescribed main frequencies and preserved contrast oscillations. In addition, the profile of each oscillation is directly controllable (e.g. sine wave, sawtooth, rectangular or any 1D profile). Our technique builds upon a reformulation of Gabor noise in terms of a phasor field that affords for a clear separation between local intensity and phase. Applications range from texturing to modeling surface displacements, as well as multi-material microstructures in the context of additive manufacturing

Modélisation implicite par squelette et applications

Modeling with skeleton is an attractive alternative to "control points" usually placed outside a shape in order to model it : this paradigm, similar to a wire inside the modeled shape, enables to create model of arbitrary geometry and topology. In order to do so, shapes defined by skeletons should be able to smoothly blend together. Introduced in computer graphics in the 90's, implicit surfaces are one of the main solution to this problem. They are powerful both for the modeling of 3D models and their animations : their construction from a skeleton and their blending capacity by simply summing their scalar field provide an easy way to incrementally create shapes and store them in a compact way, it also ease the animation containing changes in topology. Implicit surfaces, and more specifically Convolution surfaces, are therefore particularly well adapted to skeleton-based modeling. However, they present a number of drawback that make them unusable in practice. This thesis propose new skeleton-based implicit models, inspired not only by convolution but also from space deformations. They enable : – an easier generation of shape along curve skeletons (arcs of helix), – a better control of generated shape both in term of thickness and blending, in particular our model are scale-invariant that make them more intuitive, – the generation of shape which topology better reflects the topology of its skeleton, – the generation of small scale details from a procedural texture, the details behave in a coherent way with the underlying surface (and its skeleton).Modéliser avec des squelettes est une alternative très séduisante aux "points de contrôle" souvent placés à l'extérieur des formes : cette approches, analogue à un fil de fer dans une forme modelée, permet de créer des modèles de toutes géométries et topologies. Pour cela, il faut que les formes définies par chacun des squelettes soient capable de se mélanger de manière lisse. Introduites en informatique graphique dans les années 90, les surfaces implicites sont la principale solution à ce problème. Elles constituent un modèle puissant à la fois pour la modélisation d'objets tridimensionnels et pour leur animation : leur construction par squelette et leurs capacités de mélange par sommation des champs potentiels qui les définissent permettent en effet la conception progressive et le stockage compact d'objets volumiques, ainsi que l'animation de déformations pouvant comprendre des changements de topologie. Les surfaces implicites, et plus particulièrement les surfaces de convolution, forment donc un modèle particulièrement adapté à la modélisation par squelette. Toutefois, elles présentent un certain nombre de défaut qui les ont rendu inutilisable en pratique. Cette thèse propose de nouveaux modèles implicites à squelettes, s'inspirant de la convolution mais basés aussi sur des déformations de l'espace. Ils permettent : – une génération plus aisée de forme le long de squelettes formés de courbes (des arc d'hélices), – un meilleur contrôle des formes tant au niveau de leur épaisseur que de leur mélange, notamment nos modèles sont invariant par homothétie ce qui les rend plus intuitif, – la génération de surfaces ayant une topologie plus proche de celle des squelettes, – la génération de détail fins engendrés par un bruit procédural, les détails se comportant de manière cohérentes avec la surface (et les squelettes) sous-jacente

Modélisation implicite par squelette et Applications

Modeling with skeleton is an attractive alternative to "control points" usually placed outside a shape in order to model it: this paradigm, similar to a wire inside the modeled shape, enables model of arbitrary geometry and topology. In order to do so, shapes defined by skeletons should be able to smoothly blend together. Introduced in computer graphics in the 70's, implicit surfaces are one of the main solution to this problem. They are powerful both for the modeling of 3D models and their animations : their construction from a skeleton and their blending capacity by simply summing their scalar field provide an easy way to incrementally create shapes and store them in a compact way, it also facilitates animation containing changes in topology. Implicit surfaces, and more specifically Convolution surfaces, are therefore particularly well adapted to skeleton-based modeling. However, they present a number of drawback that make them difficult to use in practice. This thesis propose new skeleton-based implicit models, inspired not only by convolution but also from space deformations. They enable : - an easier generation of shape along curve skeletons (arcs of helix), - a better control of generated shape both in term of thickness and blending, in particular our model are scale-invariant that make them more intuitive, - the generation of shape which topology better reflects the topology of its skeleton, - the generation of small details from a procedural texture, the details behave in a coherent way with the underlying surface (and its skeleton).Modéliser avec des squelettes est une alternative très séduisante aux "points de contrôle" souvent placés à l'extérieur des formes : cette approche, analogue à un fil de fer dans une forme modelée, permet de créer des modèles de toutes géométries et topologies. Pour cela, il faut que les formes définies par chacun des squelettes soient capable de se mélanger de manière lisse. Introduites en informatique graphique dans les années 90, les surfaces implicites sont la principale solution à ce problème. Elles constituent un modèle puissant à la fois pour la modélisation d'objets tridimensionnels et pour leur animation: leur construction par squelette et leurs capacités de mélange par sommation des champs potentiels qui les définissent permettent en effet la conception progressive et le stockage compact d'objets volumiques, ainsi que l'animation de déformations pouvant comprendre des changements de topologie. Les surfaces implicites, et plus particulièrement les surfaces de convolution, forment donc un modèle particulièrement adapté à la modélisation par squelette. Toutefois, elles présentent un certain nombre de défaut qui les ont rendu inutilisables en pratique. Cette thèse propose de nouveaux modèles implicites à squelettes, s'inspirant de la convolution mais basés aussi sur des déformations de l'espace. Ils permettent : - une génération plus aisée de forme le long de squelettes formés de courbes (des arc d'hélices), - un meilleur contrôle des formes tant au niveau de leur épaisseur que de leur mélange, notamment - nos modèles sont invariant par homothétie ce qui les rend plus intuitif, - la génération de surfaces ayant une topologie plus proche de celle des squelettes, - la génération de détails fins engendrés par un bruit procédural, les détails se comportant de manière cohérente avec la surface (et les squelettes) sous-jacente

Synchronized-tracing of implicit surfaces

Implicit surfaces are known for their ability to represent smooth objects of arbitrary topology thanks to hierarchical combinations of primitives using a structure called a blobtree. We present a new tile-based rendering pipeline well suited for modeling scenarios, i.e., no preprocessing is required when primitive parameters are updated. When using approximate signed distance fields, we rely on compact, smooth CSG operators - extended from standard bounded operators - to compute a tight volume of interest for all primitives of the blobtree. The pipeline relies on a low-resolution A-buffer storing the primitives of interest of a given screen tile. The A-buffer is then used during ray processing to synchronize threads within a subfrustum. This allows coherent field evaluation within workgroups. We use a sparse bottom-up tree traversal to prune the blobtree on-the-fly which allows us to decorrelate field evaluation complexity from the full blobtree size. The ray processing itself is done using the sphere-tracing algorithm. The pipeline scales well to surfaces consisting of thousands of primitives