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Fabio PELLACINI

Professore Ordinario
Dipartimento di Scienze Fisiche, Informatiche e Matematiche sede ex-Matematica

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Pubblicazioni

2023 - FloralSurf: Space-Filling Geodesic Ornaments [Relazione in Atti di Convegno]
Albano, Valerio; Andrea Fanni, Filippo; Giachetti, Andrea; Pellacini, Fabio
abstract

2023 - NodeGit: Diffing and Merging Node Graphs [Articolo su rivista]
Rinaldi, Eduardo; Sforza, Davide; Pellacini, Fabio
abstract

2023 - Numerical approximations for energy preserving microfacet models [Articolo su rivista]
Sforza, Davide; Pellacini, Fabio
abstract

2023 - pEt: Direct Manipulation of Differentiable Vector Patterns [Relazione in Atti di Convegno]
Riso, Marzia; Pellacini, Fabio
abstract

2022 - BoolSurf: Boolean Operations on Surfaces [Articolo su rivista]
Riso, M.; Nazzaro, G.; Puppo, E.; Jacobson, A.; Zhou, Q.; Pellacini, F.
abstract

We port Boolean set operations between 2D shapes to surfaces of any genus, with any number of open boundaries. We combine shapes bounded by sets of freely intersecting loops, consisting of geodesic lines and cubic Bézier splines lying on a surface. We compute the arrangement of shapes directly on the surface and assign integer labels to the cells of such arrangement. Differently from the Euclidean case, some arrangements on a manifold may be inconsistent. We detect inconsistent arrangements and help the user to resolve them. Also, we extend to the manifold setting recent work on Boundary-Sampled Halfspaces, thus supporting operations more general than standard Booleans, which are well defined on inconsistent arrangements, too. Our implementation discretizes the input shapes into polylines at an arbitrary resolution, independent of the level of resolution of the underlying mesh. We resolve the arrangement inside each triangle of the mesh independently and combine the results to reconstruct both the boundaries and the interior of each cell in the arrangement. We reconstruct the control points of curves bounding cells, in order to free the result from discretization and provide an output in vector format. We support interactive usage, editing shapes consisting up to 100k line segments on meshes of up to 1M triangles.

2022 - Enforcing Energy Preservation in Microfacet Models [Relazione in Atti di Convegno]
Sforza, Davide; Pellacini, Fabio
abstract

Microfacet models suffer from a significant limitation: they only simulate a single interaction between light and surface, ignoring the subsequent scattering across the microfacets. As a consequence, the BSDF is not energy preserving, resulting in an unexpected darkening of rough specular surfaces. Energy compensation methods face this limitation by adding to the BSDF a secondary component accounting for multiple scattering contributions. While these methods are fast, robust and can be added to a renderer with relatively minor modifications, they involve the computation of the directional albedo. This quantity is expressed as an integral that does not have a closed-form solution, but it needs to be precomputed and stored in tables. These look-up tables are notoriously cumbersome to use, in particular on GPUs. This work obviates the need of look-up tables by fitting an analytic approximation of the directional albedo, which is a more practical solution. We propose a 2D rational polynomial of degree three to fit conductors and a 3D rational polynomial of degree three to fit dielectrics and materials composed of a specular layer on top of a diffuse one, such as plastics. We enforce energy preservation by rescaling the specular albedo, thus maintaining the same lobe shape. We validated our results via the furnace test, highlighting that materials rendered using our analytic approximations match almost exactly the behaviour of the ones rendered with the use of look-up tables, resulting in an energy-preserving model even at maximum roughness. The software we use to fit coefficients is open-source and can be used to fit other BSDF models as well.

2022 - Interactive and Robust Mesh Booleans [Articolo su rivista]
Cherchi, G; Pellacini, F; Attene, M; Livesu, M
abstract

Boolean operations are among the most used paradigms to create and edit digital shapes. Despite being conceptually simple, the computation of mesh Booleans is notoriously challenging. Main issues come from numerical approximations that make the detection and processing of intersection points inconsistent and unreliable, exposing implementations based on floating point arithmetic to many kinds of degeneracy and failure. Numerical methods based on rational numbers or exact geometric predicates have the needed robustness guarantees, that are achieved at the cost of increased computation times that, as of today, has always restricted the use of robust mesh Boo leans to offline applications. We introduce an algorithm for Boolean operations with robustness guarantees that is capable of operating at interactive frame rates on meshes with up to 200K triangles. We evaluate our tool thoroughly, considering not only interactive applications but also batch processing of large collections of meshes, processing of huge meshes containing millions of elements and variadic Booleans of hundreds of shapes altogether. In all these experiments, we consistently outperform prior robust floating point methods by at least one order of magnitude.

2022 - PAVEL: Decorative Patterns with Packed Volumetric Elements [Articolo su rivista]
Fanni, Filippo Andrea; Pellacini, Fabio; Scateni, Riccardo; Giachetti, Andrea
abstract

Many real-world hand-crafted objects are decorated with elements that are packed onto the object’s surface and deformed to cover it as much as possible. Examples are artisanal ceramics and metal jewelry. Inspired by these objects, we present a method to enrich surfaces with packed volumetric decorations. Our algorithm works by first determining the locations in which to add the decorative elements and then removing the non-physical overlap between them while preserving the decoration volume. For the placement, we support several strategies depending on the desired overall motif. To remove the overlap, we use an approach based on implicit deformable models creating the qualitative effect of plastic warping while avoiding expensive and hard-to-control physical simulations. Our decorative elements can be used to enhance virtual surfaces, as well as 3D-printed pieces, by assembling the decorations onto real surfaces to obtain tangible reproductions.

2022 - b/Surf: Interactive Bzier Splines on Surface Meshes [Articolo su rivista]
Mancinelli, Claudio; Nazzaro, Giacomo; Pellacini, Fabio; Puppo, Enrico
abstract

We present a practical framework to port Bzier curves to surfaces. We support the interactive drawing and editing of Bzier splines on manifold meshes with millions of triangles, by relying on just repeated manifold averages. We show that direct extensions of the de Casteljau and Bernstein evaluation algorithms to the manifold setting are fragile, and prone to discontinuities when control polygons become large. Conversely, approaches based on subdivision are robust and can be implemented efficiently. We implement manifold extensions of the recursive de Casteljau bisection, and an open-uniform Lane-Riesenfeld subdivision scheme. For both schemes, we present algorithms for curve tracing, point evaluation, and approximated point insertion. We run bulk experiments to test our algorithms for robustness and performance, and we compare them with other methods at the state of the art, always achieving correct results and superior performance. For interactive editing, we port all the basic user interface interactions found in 2D tools directly to the mesh. We also support mapping complex SVG drawings to the mesh and their interactive editing.

2022 - geoTangle: Interactive Design of Geodesic Tangle Patterns on Surfaces [Articolo su rivista]
Nazzaro, Giacomo; Puppo, Enrico; Pellacini, Fabio
abstract

Tangles are complex patterns, which are often used to decorate the surface of real-world artisanal objects. They consist of arrangements of simple shapes organized into nested hierarchies, obtained by recursively splitting regions to add progressively finer details. In this article, we show that 3D digital shapes can be decorated with tangles by working interactively in the intrinsic metric of the surface. Our tangles are generated by the recursive application of only four operators, which are derived from tracing the isolines or the integral curves of geodesics fields generated from selected seeds on the surface. Based on this formulation, we present an interactive application that lets designers model complex recursive patterns directly on the object surface without relying on parametrization. We reach interactive speed on meshes of a few million triangles by relying on an efficient approximate graph-based geodesic solver.

2022 - pOp: Parameter Optimization of Differentiable Vector Patterns [Articolo su rivista]
Riso, M.; Sforza, D.; Pellacini, F.
abstract

Procedural materials are extensively used in computer graphics, since they provide editable, resolution-independent representation of textures. However, tuning the parameters of procedural generators to achieve a desired result remains time-consuming for users. Recently, inverse procedural material algorithms have been developed, exploiting differentiable rendering methods to find the parameters of a procedural model that match a target image. These approaches focus on raster textures. We propose pOp, a practical method for estimating the parameters of vector patterns, that are formed by collections of vector shapes arranged by an arbitrary procedural program. In our approach, patterns are defined as arbitrary programs, that control the translation, rotation and scale or vector graphics elements. We support elements typical of vector graphics, namely points, lines, circle, rounded rectangles, and quadratic Bèzier drawings, in multiple colors. We optimize the program parameters by automatically differentiating the signed distance field of the drawing, which we found to be significantly more reliable than using differentiable rendering of the final image. We demonstrate our method on a variety of cases, representing the variations found in structured vector patterns.

2021 - Joint workshop on Games-Human Interaction (GHItaly21) and multi-party interaction in eXtended reality (MIXR) [Relazione in Atti di Convegno]
Ripamonti, L. A.; Gadia, D.; Meggiorini, D.; Mariani, I.; De Marsico, M. D.; Mancini, M.; Pellacini, F.; Varni, G.; Murphy, D.; Maye, L.; O'Toole, P.
abstract

This paper shortly summarizes the research lines underlining the joint workshop held at CHItaly 2021 with title "Joint workshop on Games-Human Interaction (GHItaly21) and Multi-party Interaction in eXtended Reality (MIXR)", and sketched the expected contributions.

2020 - Neural reflectance transformation imaging [Articolo su rivista]
Dulecha, T. G.; Fanni, F. A.; Ponchio, F.; Pellacini, F.; Giachetti, A.
abstract

Reflectance transformation imaging (RTI) is a computational photography technique widely used in the cultural heritage and material science domains to characterize relieved surfaces. It basically consists of capturing multiple images from a fixed viewpoint with varying lights. Handling the potentially huge amount of information stored in an RTI acquisition that consists typically of 50–100 RGB values per pixel, allowing data exchange, interactive visualization, and material analysis, is not easy. The solution used in practical applications consists of creating “relightable images” by approximating the pixel information with a function of the light direction, encoded with a small number of parameters. This encoding allows the estimation of images relighted from novel, arbitrary lights, with a quality that, however, is not always satisfactory. In this paper, we present NeuralRTI, a framework for pixel-based encoding and relighting of RTI data. Using a simple autoencoder architecture, we show that it is possible to obtain a highly compressed representation that better preserves the original information and provides increased quality of virtual images relighted from novel directions, especially in the case of challenging glossy materials. We also address the problem of validating the relight quality on different surfaces, proposing a specific benchmark, SynthRTI, including image collections synthetically created with physical-based rendering and featuring objects with different materials and geometric complexity. On this dataset and as well on a collection of real acquisitions performed on heterogeneous surfaces, we demonstrate the advantages of the proposed relightable image encoding.

2020 - XR-Cockpit: A comparison of VR and AR solutions on an interactive training station [Relazione in Atti di Convegno]
Caputo, A.; Jacota, S.; Krayevskyy, S.; Pesavento, M.; Pellacini, F.; Giachetti, A.
abstract

One of the most challenging aspects of the implementation of Virtual/Mixed reality training systems is the effective simulation of real-world manipulation of the physical devices included in control interfaces like buttons, sliders, levers, knobs, etc. In this paper we describe a mockup airplane cockpit (XR-Cockpit), featuring interactive components of this kind that demonstrate the feasibility of effective simulations of device manipulation using low cost hand tracking technology and gesture recognition. Based on this system, we performed a user study to compare the effectiveness of the interaction with virtual tools using different visualization solutions: immersive VR, optical and video see-through based MR. In our study, we also checked how well it is possible to perform manipulation of real objects wearing the two video see-through solutions. The analysis of the experimental results provides useful guidelines for the design of Virtual and Mixed Reality training systems involving virtual and physical actions on manipulation devices.

2019 - Grammar-based procedural animations for motion graphics [Articolo su rivista]
Carra, Edoardo; Santoni, Christian; Pellacini, Fabio
abstract

Abstact Motion graphics are a form of animation where several sets of shapes are choreographed together using a wide range of effects to produce compelling footage. We present a method to procedurally generate motion graphics. We formally model motion graphics with timeslice grammars, an extension of split and group grammars, that are able to control and manipulate both the temporal and spatial components of an animation. We are able to combine both these aspects by representing animations as sets of affine transformations sampled uniformly in both space and time. These transformations are controlled by the grammar. Shapes in our system are represented as highly tessellated polygons, and are animated by applying the affine transforms to each shape vertex given the vertex position and the animation time. We introduce a small set of operators showing how we can produce convincing animations, combining the expressive power of the grammar model, the composability of the operators with themselves, and the capabilities that derive from our shape representation. Throughout the paper, we show how timeslice grammars can, in few tens of seconds, produce a wide variety of animations that would take artists hours of tedious and time-consuming work.

2019 - SceneGit: a practical system for diffing and merging 3D environments [Articolo su rivista]
Edoardo, Carra; Pellacini, Fabio
abstract

Version control systems are the foundation of collaborative workflows for text documents. For 3D environments though, version control is still an open problem due to the heterogeneous data of 3D scenes and their size. In this paper, we present a practical version control system for 3D scenes comprised of shapes, materials, textures, and animations, combined together in scene graphs. We version objects at their finest granularity, to make repositories smaller and to allow artists to work concurrently on the same object. Since, for some scene data, computing an optimal set of changes between versions is not computationally feasible, version control systems use heuristics. Compared to prior work, we propose heuristics that are efficient, robust, and independent of the application. We test our system on a variety of large scenes edited with different workflows, and show that our approach can handle all cases well while remaining efficient as scene size increases. Compared to prior work, we are significantly faster and more robust. A user study confirms that our system aids collaboration.

2019 - Texel-Att: representing and classifying element-based textures by attributes [Relazione in Atti di Convegno]
Godi, Marco; Joppi, Christian; Giachetti, Andrea; Pellacini, Fabio; Cristani, Marco
abstract

Element-based textures are a kind of texture formed by nameable elements, the texels [1], distributed according to specific statistical distributions; it is of primary importance in many sectors, namely textile, fashion and interior design industry. State-of-theart texture descriptors fail to properly characterize element-based texture, so we present Texel-Att to fill this gap. Texel-Att is the first fine-grained, attribute-based representation and classification framework for element-based textures. It first individuates texels, characterizing them with individual attributes; subsequently, texels are grouped and characterized through layout attributes, which give the Texel-Att representation. Texels are detected by a Mask-RCNN, trained on a brand-new element-based texture dataset, ElBa, containing 30K texture images with 3M fully-annotated texels. Examples of individual and layout attributes are exhibited to give a glimpse on the level of achievable graininess. In the experiments, we present detection results to show that texels can be precisely individuated, even on textures "in the wild"; to this sake, we individuate the element-based classes of the Describable Texture Dataset (DTD), where almost 900K texels have been manually annotated, leading to the Element-based DTD (E-DTD). Subsequently, classification and ranking results demonstrate the expressivity of Texel-Att on ElBa and E-DTD, overcoming the alternative features and relative attributes, doubling the best performance in some cases; finally, we report interactive search results on ElBa and E-DTD: with Texel-Att on the E-DTD dataset we are able to individuate within 10 iterations the desired texture in the 90% of cases, against the 71% obtained with a combination of the finest existing attributes so far. Dataset and code is available at https://github.com/godimarcovr/Texel-Att

2019 - Texture retrieval in the wild through detection-based attributes [Relazione in Atti di Convegno]
Joppi, Christian; Godi, Marco; Giachetti, Andrea; Pellacini, Fabio; Cristani, Marco
abstract

Capturing the essence of a textile image in a robust way is important to retrieve it in a large repository, especially if it has been acquired in the wild (by taking a photo of the textile of interest). In this paper we show that a texel-based representation fits well with this task. In particular, we refer to Texel-Att, a recent texel-based descriptor which has shown to capture fine grained variations of a texture, for retrieval purposes. After a brief explanation of Texel-Att, we will show in our experiments that this descriptor is robust to distortions resulting from acquisitions in the wild by setting up an experiment in which textures from the ElBa (an Element-Based texture dataset) are artificially distorted and then used to retrieve the original image. We compare our approach with existing descriptors using a simple ranking framework based on distance functions. Results show that even under extreme conditions (such as a down-sampling with a factor of 10), we perform better than alternative approaches.

2019 - Yocto/GL: a data-oriented library for physically-based graphics [Relazione in Atti di Convegno]
Pellacini, Fabio; Nazzaro, Giacomo; Carra, Edoardo
abstract

In this paper we present Yocto/GL, a software library for computer graphics research and education. The library is written in C++ and targets execution on the CPU, with support for basic math, geometry and imaging utilities, path tracing and file IO. What distinguishes Yocto/GL from other similar projects is its minimalistic design and data-oriented programming style, which makes the library readable, extendible, and efficient. We developed Yocto/GL to meet our need, as a research group, of a simple and reliable codebase that lets us experiment with ease on research projects of various kind. After many iterations carried out over a few years, we settled on a design that we find effective for our purposes. In the hope of making our efforts valuable for the community, we share our experience in the development and make the library publicly available.

2018 - LevelMerge: Collaborative Game Level Editing by Merging Labeled Graphs [Articolo su rivista]
Santoni, C.; Salvati, G.; Tibaldo, V.; Pellacini, F.
abstract

Game development is commonly seen as a collaborative effort, with teams cooperating on the same project. Nowadays, a variety of cloud-based services have shown the benefits of performing tasks in real-time collaboration with others. In this article, we present a system for collaborative game level editing. We model this problem as a special instance of merging labeled directed acyclic graphs. We propose an algorithm that guarantees that the shared game level is always coherent between edits, both hierarchically and semantically. We establish real-time collaboration by initiating merges automatically and by augmenting the game editor interface to allow users to monitor all others edits in real time. We validate our algorithm by merging complex edits and large game levels. We further validate the collaborative workflow by running a user study with expert game developers, showing that our system works well and collaborative workflows are beneficial to game development.

2018 - gMotion: A spatio-temporal grammar for the procedural generation of motion graphics [Relazione in Atti di Convegno]
Carra, Edoardo; Santoni, Christian; Pellacini, Fabio
abstract

Creating by hand compelling 2D animations that choreograph several groups of shapes requires a large number of manual edits. We present a method to procedurally generate motion graphics with timeslice grammars. Timeslice grammars are to time what split grammars are to space. We use this grammar to formally model motion graphics, manipulating them in both temporal and spatial components. We are able to combine both these aspects by representing animations as sets of affine transformations sampled uniformly in both space and time. Rules and operators in the grammar manipulate all spatio-temporal matrices as a whole, allowing us to expressively construct animation with few rules. The grammar animates shapes, which are represented as highly tessellated polygons, by applying the affine transforms to each shape vertex given the vertex position and the animation time. We introduce a small set of operators showing how we can produce 2D animations of geometric objects, by combining the expressive power of the grammar model, the composability of the operators with themselves, and the capabilities that derive from using a unified spatio-temporal representation for animation data. Throughout the paper, we show how timeslice grammars can produce a wide variety of animations that would take artists hours of tedious and time-consuming work. In particular, in cases where change of shapes is very common, our grammar can add motion detail to large collections of shapes with greater control over per-shape animations along with a compact rules structure.

2017 - sLayer: a System for Multi-Layered Material Sculpting [Relazione in Atti di Convegno]
Calabrese, Claudio; Fratarcangeli, Marco; Pellacini, Fabio
abstract

Many real world materials have a stratified structure, composed by the proximity and the interaction of multiple highly-detailed layers. Example of these materials are peeling paint, old tree bark and rusted metals. While digital sculpting is particularly well-suited to model these aged surfaces, the interaction between layers is not accounted for. We present a system for sculpting multi-layers materials where collision between layers are handled interactively while brushing meshes that scales up to the million of polygons necessary to model aged surfaces. We do so by observing that if the average mean edge length is maintained constant throughout the modeling session, we can use a single data structure, namely a uniform grid, to accelerate all the sculpting operations. We present a brush rasterization pipeline that uses this data structure for multi-layer editing. We also show that by adding a few interface tools for layer creation and selection, we can create detailed surface similar to real-world ones. To the best of our knowledge, our work is the first to show sculpting of highly-detailed, multi-layered materials in real-time.

2016 - State of the art in artistic editing of appearance, lighting and material [Articolo su rivista]
Schmidt, Thorsten Walther; Pellacini, Fabio; Nowrouzezahrai, Derek; Jarosz, Wojciech; Dachsbacher, Carsten
abstract

Mimicking the appearance of the real world is a longstanding goal of computer graphics, with several important applications in the feature film, architecture and medical industries. Images with well-designed shading are an important tool for conveying information about the world, be it the shape and function of a computer-aided design (CAD) model, or the mood of a movie sequence. However, authoring this content is often a tedious task, even if undertaken by groups of highly trained and experienced artists. Unsurprisingly, numerous methods to facilitate and accelerate this appearance editing task have been proposed, enabling the editing of scene objects' appearances, lighting and materials, as well as entailing the introduction of new interaction paradigms and specialized preview rendering techniques. In this review, we provide a comprehensive survey of artistic appearance, lighting and material editing approaches. We organize this complex and active research area in a structure tailored to academic researchers, graduate students and industry professionals alike. In addition to editing approaches, we discuss how user interaction paradigms and rendering back ends combine to form usable systems for appearance editing. We conclude with a discussion of open problems and challenges to motivate and guide future research. Mimicking the appearance of the real world is a longstanding goal of computer graphics, with several important applications in the feature film, architecture and medical industries. Images with well-designed shading are an important tool for conveying information about the world, be it the shape and function of a computer-aided design (CAD) model, or the mood of a movie sequence. However, authoring this content is often a tedious task, even if undertaken by groups of highly trained and experienced artists. Unsurprisingly, numerous methods to facilitate and accelerate this appearance editing task have been proposed, enabling the editing of scene objects' appearances, lighting and materials, as well as entailing the introduction of new interaction paradigms and specialized preview rendering techniques. In this review we provide a comprehensive survey of artistic appearance, lighting, and material editing approaches. We organize this complex and active research area in a structure tailored to academic researchers, graduate students, and industry professionals alike. In addition to editing approaches, we discuss how user interaction paradigms and rendering backends combine to form usable systems for appearance editing. We conclude with a discussion of open problems and challenges to motivate and guide future research. © 2015 The Eurographics Association and John Wiley & Sons Ltd.

2016 - Vivace: A Practical Gauss-seidel Method for Stable Soft Body Dynamics [Articolo su rivista]
Fratarcangeli, Marco; Tibaldo, Valentina; Pellacini, Fabio
abstract

The solution of large sparse systems of linear constraints is at the base of most interactive solvers for physically-based animation of soft body dynamics. We focus on applications with hard and tight per-frame resource budgets, such as video games, where the solution of soft body dynamics needs to be computed in a few milliseconds. Linear iterative methods are preferred in these cases since they provide approximate solutions within a given error tolerance and in a short amount of time. We present a parallel randomized Gauss-Seidel method which can be effectively employed to enable the animation of 3D soft objects discretized as large and irregular triangular or tetrahedral meshes. At the beginning of each frame, we partition the set of equations governing the system using a randomized graph coloring algorithm. The unknowns in the equations belonging to the same partition are independent of each other. Then, all the equations belonging to the same partition are solved at the same time in parallel. Our algorithm runs completely on the GPU and can support changes in the constraints topology. We tested our method as a solver for soft body dynamics within the Projective Dynamics and Position Based Dynamics frameworks. We show how the algorithmic simplicity of this iterative strategy enables great numerical stability and fast convergence speed, which are essential features for physically based animations with fixed and small hard time budgets. Compared to the state of the art, we found our method to be faster and scale better while providing stabler solutions for very small time budgets.

2016 - cSculpt: a system for collaborative sculpting [Articolo su rivista]
Calabrese, Claudio; Salvati, Gabriele; Tarini, Marco; Pellacini, Fabio
abstract

Collaborative systems are well established solutions for sharing work among people. In computer graphics these workflows are still not well established, compared to what is done for text writing or software development. Usually artists work alone and share their final models by sending files. In this paper we present a system for collaborative 3D digital sculpting. In our prototype, multiple artists concurrently sculpt a polygonal mesh on their local machines by changing its vertex properties, such as positions and material BRDFs. Our system shares the artists' edits automatically and seamlessly merges these edits even when they happen on the same region of the surface. We propose a merge algorithm that is fast-enough for seamless collaboration, respects users' edits as much as possible, can support any sculpting operation, and works for both geometry and appearance modifications. Since in sculpting artists alternatively perform fine adjustments and large scale modifications, our algorithm is based on a multiresolution edit representation that handles concurrent overlapping edits at different scales. We tested our algorithm by modeling meshes collaboratively in different sculpting sessions and found that our algorithm outperforms prior works on collaborative mesh editing in all cases. © 2016 ACM.

2016 - gTangle: a grammar for the procedural generation of tangle patterns [Articolo su rivista]
Santoni, Christian; Pellacini, Fabio
abstract

Tangles are a form of structured pen-and-ink 2D art characterized by repeating, recursive patterns. We present a method to procedurally generate tangle drawings, seen as recursively split sets of arbitrary 2D polygons with holes, with anisotropic and non-stationary features. We formally model tangles with group grammars, an extension of set grammars, that explicitly handles the grouping of shapes necessary to represent tangle repetitions. We introduce a small set of expressive geometric and grouping operators, showing that they can respectively express complex tangles patterns and sub-pattern distributions, with relatively simple grammars. We also show how users can control tangle generation in an interactive and intuitive way. Throughout the paper, we show how group grammars can, in few tens of seconds, produce a wide variety of patterns that would take artists hours of tedious and time-consuming work. We then validated both the quality of the generated tangles and the efficiency of the control provided to the users with a user study, run with both expert and non-expert users.

2015 - 3DFlow: continuous summarization of mesh editing workflows [Articolo su rivista]
Denning, Jonathan; Tibaldo, Valentina; Pellacini, Fabio
abstract

Mesh editing software is improving, allowing skilled artists to create detailed meshes efficiently. For a variety of reasons, artists are interested in sharing not just their final mesh but also their whole workflow, though the common media for sharing has limitations. In this paper, we present 3DFlow, an algorithm that computes continuous summarizations of mesh editing workflows. 3DFlow takes as input a sequence of meshes and outputs a visualization of the workflow summarized at any level of detail. The output is enhanced by highlighting edited regions and, if provided, overlaying visual annotations to indicated the artist's work, e.g. summarizing brush strokes in sculpting. We tested 3DFlow with a large set of inputs using a variety of mesh editing techniques, from digital sculpting to low-poly modeling, and found 3DFlow performed well for all. Furthermore, 3DFlow is independent of the modeling software used because it requires only mesh snapshots, and uses the additional information only for optional overlays. We release 3DFlow as open source for artists to showcase their work and release all our datasets so other researchers can improve upon our work.

2015 - GReTA -- A novel global and recursive tracking algorithm in three dimensions [Articolo su rivista]
Attanasi, Alessandro; Cavagna, Andrea; Del Castello, Lorenzo; Giardina, irene rosana; Jelic, Asja; Melillo, Stefania; Parisi, Leonardo; Pellacini, Fabio; Shen, Edward; Silvestri, Edmondo; Viale, Massimiliano
abstract

Tracking multiple moving targets allows quantitative measure of the dynamic behavior in systems as diverse as animal groups in biology, turbulence in fluid dynamics and crowd and traffic control. In three dimensions, tracking several targets becomes increasingly hard since optical occlusions are very likely, i.e., two featureless targets frequently overlap for several frames. Occlusions are particularly frequent in biological groups such as bird flocks, fish schools, and insect swarms, a fact that has severely limited collective animal behavior field studies in the past. This paper presents a 3D tracking method that is robust in the case of severe occlusions. To ensure robustness, we adopt a global optimization approach that works on all objects and frames at once. To achieve practicality and scalability, we employ a divide and conquer formulation, thanks to which the computational complexity of the problem is reduced by orders of magnitude. We tested our algorithm with synthetic data, with experimental data of bird flocks and insect swarms and with public benchmark datasets, and show that our system yields high quality trajectories for hundreds of moving targets with severe overlap. The results obtained on very heterogeneous data show the potential applicability of our method to the most diverse experimental situations.

2015 - MeshHisto: collaborative modeling by sharing and retargeting editing histories [Articolo su rivista]
Salvati, Gabriele; Santoni, Christian; Tibaldo, Valentina; Pellacini, Fabio
abstract

Current modeling packages have polished interfaces for editing polygonal meshes, where artists work individually on each mesh. A variety of recent cloud-based services have shown the benefits of editing documents in real-time collaboration with others. In this paper, we present a system for collaborative editing of low-polygonal and subdivision mesh models. We cast collaborative editing as a special instance of distributed version control. We support concurrent editing by robustly sharing and merging mesh version histories in real-time. We store and transmit mesh differences efficiently by encoding them as sequences of primitive editing operations. We enable collaboration by merging and detecting conflicts. We extend this model letting artists adapt others’ editing histories by retargeting sequences of editing operations to new parts of the mesh with potentially different topology. We tested our algorithms by editing meshes with up to thousand edits, in collaborative editing sessions lasting a few hours, and by retargeting sequences of several hundred edits. We found the proposed system to be reliable, fast and scaling well with mesh complexity. We demonstrate that our merge algorithm is more robust than prior work. We further validated the proposed collaborative workflow with a user study where MeshHisto was consistently preferred over other alternatives for collaborative workflows.

2015 - Scalable partitioning for parallel position based dynamics [Articolo su rivista]
Fratarcangeli, M.; Pellacini, Fabio
abstract

We introduce a practical partitioning technique designed for parallelizing Position Based Dynamics, and exploiting the ubiquitous multi-core processors present in current commodity GPUs. The input is a set of particles whose dynamics is influenced by spatial constraints. In the initialization phase, we build a graph in which each node corresponds to a constraint and two constraints are connected by an edge if they influence at least one common particle. We introduce a novel greedy algorithm for inserting additional constraints (phantoms) in the graph such that the resulting topology is q-colourable, where ˆ qˆ ≥ 2 is an arbitrary number. We color the graph, and the constraints with the same color are assigned to the same partition. Then, the set of constraints belonging to each partition is solved in parallel during the animation phase. We demonstrate this by using our partitioning technique; the performance hit caused by the GPU kernel calls is significantly decreased, leaving unaffected the visual quality, robustness and speed of serial position based dynamics.

2014 - AppIm: Linear Spaces for Image-based Appearance Editing [Articolo su rivista]
DI RENZO, Francesco; Calabrese, Claudio; Pellacini, Fabio
abstract

2014 - How Do People Edit Light Fields? [Articolo su rivista]
Adrian, Jarabo; Belen, Masia; Adrien, Bousseau; Pellacini, Fabio; Diego, Gutierrez
abstract

We present a thorough study to evaluate different light field editing interfaces, tools and workflows from a user perspective. This is of special relevance given the multidimensional nature of light fields, which may make common image editing tasks become complex in light field space. We additionally investigate the potential benefits of using depth information when editing, and the limitations imposed by imperfect depth reconstruction using current techniques. We perform two different experiments, collecting both objective and subjective data from a varied number of editing tasks of increasing complexity based on local point-and-click tools. In the first experiment, we rely on perfect depth from synthetic light fields, and focus on simple edits. This allows us to gain basic insight on light field editing, and to design a more advanced editing interface. This is then used in the second experiment, employing real light fields with imperfect reconstructed depth, and covering more advanced editing tasks. Our study shows that users can edit light fields with our tested interface and tools, even in the presence of imperfect depth. They follow different workflows depending on the task at hand, mostly relying on a combination of different depth cues. Last, we confirm our findings by asking a set of artists to freely edit both real and synthetic light fields.

2014 - State of the Art in Artistic Editing of Appearance, Lighting, and Material [Relazione in Atti di Convegno]
T., Schmidt; Pellacini, Fabio; D., Nowrouzezahrai; W., Jarosz; C., Dachsbacher
abstract

2014 - Toward Evaluating the Usefulness of Global Illumination for Novices in Lighting Design Tasks [Articolo su rivista]
Ondrej, Karlik; Martin, Ruzicka; Vaclav, Gassenbauer; Pellacini, Fabio; Jaroslav, Krivanek
abstract

Thanks to its ability to improve the realism of computer-generated imagery, the use of global illumination has recently become widespread among digital lighting artists. It remains unclear, though, what impact it has on the lighting design workflows, especially for novice users. In this paper we present a user study which investigates the use of global illumination, large area lights, and non-physical fill lights in lighting design tasks, where 26 novice subjects design lighting with these tools. The collected data suggest that global illumination is not significantly harder to control for novice users that direct illumination, and when given the possibility, most users opt to use it in their designs. The use of global illumination together with large area lights leads to simpler lighting setups with fewer non-physical fill lights. Interestingly, global illumination does not supersede fill lights: users still include them into their globally illuminated lighting setups. We believe that our results will find use in the development of lighting design tools for non-expert users.

2014 - Towards a Massively Parallel Solver for Position Based Dynamics [Relazione in Atti di Convegno]
M., Fratarcangeli; Pellacini, Fabio
abstract

2013 - Bi-Scale Appearance Fabrication [Articolo su rivista]
Yanxiang, Lan; Yue, Dong; Pellacini, Fabio; Xin, Tong
abstract

Surfaces in the real world exhibit complex appearance due to spatial variations in both their reflectance and local shading frames (i.e. the local coordinate system defined by the normal and tangent direction). For opaque surfaces, existing fabrication solutions can reproduce well only the spatial variations of isotropic reflectance. In this paper, we present a system for fabricating surfaces with desired spatially-varying reflectance, including anisotropic ones, and local shading frames. We approximate each input reflectance, rotated by its local frame, as a small patch of oriented facets coated with isotropic glossy inks. By assigning different ink combinations to facets with different orientations, this bi-scale material can reproduce a wider variety of reflectance than the printer gamut, including anisotropic materials. By orienting the facets appropriately, we control the local shading frame. We propose an algorithm to automatically determine the optimal facets orientations and ink combinations that best approximate a given input appearance, while obeying manufacturing constraints on both geometry and ink gamut. We fabricate the resulting surface with commercially available hardware, a 3D printer to fabricate the facets and a flatbed UV printer to coat them with inks. We validate our method by fabricating a variety of isotropic and anisotropic materials with rich variations in normals and tangents.

2013 - EnvyDepth: an interface for recovering local natural illumination from environment maps [Articolo su rivista]
Banterle, Francesco; Callieri, Marco; Dellepiane, Matteo; Corsini, M; Pellacini, Fabio; Scopigno, Roberto
abstract

In this paper, we present EnvyDepth, an interface for recovering local illumination from a single HDR environment map. In EnvyDepth, the user quickly indicates strokes to mark regions of the environment map that should be grouped together in a single geometric primitive. From these annotated strokes, EnvyDepth uses edit propagation to create a detailed collection of virtual point lights that reproduce both the local and the distant lighting effects in the original scene. When compared to the sole use of the distant illumination, the added spatial information better reproduces a variety of local effects such as shadows, highlights and caustics. Without the effort needed to create precise scene reconstructions, EnvyDepth annotations take only tens of seconds to produce a plausible lighting without visible artifacts. This is easy to obtain even in the case of complex scenes, both indoors and outdoors. The generated lighting environments work well in a production pipeline since they are efficient to use and able to produce accurate renderings.

2013 - MeshGit: Diffing and Merging Meshes for Polygonal Modeling [Articolo su rivista]
Jonathan D., Denning; Pellacini, Fabio
abstract

This paper presents MeshGit, a practical algorithm for diffing and merging polygonal meshes typically used in subdivision modeling workflows. Inspired by version control for text editing, we introduce the mesh edit distance as a measure of the dissimilarity between meshes. This distance is defined as the minimum cost of matching the vertices and faces of one mesh to those of another. We propose an iterative greedy algorithm to approximate the mesh edit distance, which scales well with model complexity, providing a practical solution to our problem. We translate the mesh correspondence into a set of mesh editing operations that transforms the first mesh into the second. The editing operations can be displayed directly to provide a meaningful visual difference between meshes. For merging, we compute the difference between two versions and their common ancestor, as sets of editing operations. We robustly detect conflicting operations, automatically apply non-conflicting edits, and allow the user to choose how to merge the conflicting edits. We evaluate MeshGit by diffing and merging a variety of meshes and find it to work well for all.

2012 - Ishair: Importance sampling for hair scattering [Articolo su rivista]
Jiawei, Ou; Xie, Feng; Krishnamachari, Parashar; Pellacini, Fabio
abstract

We present an importance sampling method for the bidirectional scattering distribution function (bsdf) of hair. Our method is based on the multi-lobe hair scattering model presented by Sadeghi et al. . We reduce Noise by drawing samples from a distribution that approximates the bsdf well. Our algorithm is efficient and Easy to implement, since the sampling process requires only the evaluation of a few analytic functions, with no Significant memory overhead or need for precomputation. We tested our method in a research raytracer and a Production renderer based on micropolygon rasterization. We show significant improvements for rendering direct Illumination using multiple importance sampling and for rendering indirect illumination using path tracing. © 2012 The Author(s).

2012 - Printing spatially-varying reflectance for reproducing HDR images [Articolo su rivista]
Dong, Yue; Tong, Xin; Pellacini, Fabio; Baining, Guo
abstract

We present a solution for viewing high dynamic range (HDR) images with spatially-varying distributions of glossy materials printed on reflective media. Our method exploits appearance variations of the glossy materials in the angular domain to display the input HDR image at different exposures. As viewers change the print orientation or lighting directions, the print gradually varies its appearance to display the image content from the darkest to the brightest levels. Our solution is based on a commercially available printing system and is fully automatic. Given the input HDR image and the BRDFs of a set of available inks, our method computes the optimal exposures of the HDR image for all viewing conditions and the optimal ink combinations for all pixels by minimizing the difference of their appearances under all viewing conditions. We demonstrate the effectiveness of our method with print samples generated from different inputs and visualized under different viewing and lighting conditions. © 2012 ACM 0730-0301/2012/08-ART40.

2011 - AppGen: Interactive Material Modeling from a Single Image [Articolo su rivista]
Yue, Dong; Xin, Tong; Pellacini, Fabio; Baining, Guo
abstract

We present AppGen, an interactive system for modeling materials from a single image. Given a texture image of a nearly planar surface lit with directional lighting, our system models the detailed spatially-varying reflectance properties (diffuse, specular and roughness) and surface normal variations with minimal user interaction. We ask users to indicate global shading and reflectance information by roughly marking the image with a few user strokes, while our system assigns reflectance properties and normals to each pixel. We first interactively decompose the input image into the product of a diffuse albedo map and a shading map. A two-scale normal reconstruction algorithm is then introduced to recover the normal variations from the shading map and preserve the geometric features at different scales. We finally assign the specular parameters to each pixel guided by user strokes and the diffuse albedo. Our system generates convincing results within minutes of interaction and works well for a variety of material types that exhibit different reflectance and normal variations, including natural surfaces and man-made ones.

2011 - AppWarp: Retargeting Measured Materials by Appearance-Space Warping [Articolo su rivista]
Xiaobo, An; Xin, Tong; Jonathan D., Denning; Pellacini, Fabio
abstract

We propose a method for retargeting measured materials, where a source measured material is edited by applying the reflectance functions of a template measured dataset. The resulting dataset is a material that maintains the spatial patterns of the source dataset, while exhibiting the reflectance behaviors of the template. Compared to editing materials by subsequent selections and modifications, retargeting shortens the time required to achieve a desired look by directly using template data, just as color transfer does for editing images. With our method, users have to just mark corresponding regions of source and template with rough strokes, with no need for further input. This paper introduces AppWarp, an algorithm that achieves retargeting as a user-constrained, appearance-space warping operation, that executes in tens of seconds. Our algorithm is independent of the measured material representation and supports retargeting of analytic and tabulated BRDFs as well as BSSRDFs. In addition, our method makes no assumption of the data distribution in appearance-space nor on the underlying correspondence between source and target. These characteristics make AppWarp the first general formulation for appearance retargeting. We validate our method on several types of materials, including leaves, metals, waxes, woods and greeting cards. Furthermore, we demonstrate how retargeting can be used to enhance diffuse texture with high quality reflectance.

2011 - LightSlice: Matrix Slice Sampling for the Many-Lights Problem [Articolo su rivista]
Jiawei, Ou; Pellacini, Fabio
abstract

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2011 - MeshFlow: Interactive visualization of mesh construction sequences [Articolo su rivista]
Jonathan D., Denning; William B., Kerr; Pellacini, Fabio
abstract

The construction of polygonal meshes remains a complex task in Computer Graphics, taking tens of thousands of individual operations over several hours of modeling time. The complexity of modeling in terms of number of operations and time makes it difficult for artists to understand all details of how meshes are constructed. We present MeshFlow, an interactive system for visualizing mesh construction sequences. MeshFlow hierarchically clusters mesh editing operations to provide viewers with an overview of the model construction while still allowing them to view more details on demand. We base our clustering on an analysis of the frequency of repeated operations and implement it using substituting regular expressions. By filtering operations based on either their type or which vertices they affect, MeshFlow also ensures that viewers can interactively focus on the relevant parts of the modeling process. Automatically generated graphical annotations visualize the clustered operations. We have tested MeshFlow by visualizing five mesh sequences each taking a few hours to model, and we found it to work well for all. We have also evaluated MeshFlow with a case study using modeling students. We conclude that our system provides useful visualizations that are found to be more helpful than video or document-form instructions in understanding mesh construction. © 2011 ACM.

2010 - BendyLights: Artistic Control of Direct Illumination by Curving Light Rays [Articolo su rivista]
William B., Kerr; Pellacini, Fabio; Jonathan D., Denning
abstract

2010 - Fabricating spatially-varying subsurface scattering [Articolo su rivista]
Yue, Dong; Jiaping, Wang; Pellacini, Fabio; Xin, Tong; Baining, Guo
abstract

2010 - SafeGI: Type Checking to Improve Correctness in Rendering System Implementation [Articolo su rivista]
Jiawei, Ou; Pellacini, Fabio
abstract

2010 - Toward evaluating material design interface paradigms for novice users [Articolo su rivista]
William B., Kerr; Pellacini, Fabio
abstract

2010 - User Controllable Color Transfer [Articolo su rivista]
Xiaobo, An; Pellacini, Fabio
abstract

This paper presents an image editing framework where users use reference images to indicate desired color edits. In our approach, users specify pairs of strokes to indicate corresponding regions in both the original and the reference image that should have the same color “style”. Within each stroke pair, a nonlinear constrained parametric transfer model is used to transfer the reference colors to the original. We estimate the model parameters by matching color distributions, under constraints that ensure no visual artifacts are present in the transfer result. To perform transfer on the whole image, we employ optimization methods to propagate the model parameters defined at each stroke location to spatially-close regions of similar appearance. This stroke-based formulation requires minimal user effort while retaining the high degree of user control necessary to allow artistic interpretations. We demonstrate our approach by performing color transfer on a number of image pairs varying in content and style, and show that our algorithm outperforms state-of-the-art color transfer methods on both user-controllability and visual qualities of the transfer results.

2010 - Visibility Editing For All-Frequency Shadow Design [Articolo su rivista]
Juraj, Obert; Pellacini, Fabio; Sumanta, Pattanaik
abstract

2010 - envyLight: an interface for editing natural illumination [Articolo su rivista]
Pellacini, Fabio
abstract

2009 - Printing Spatially-Varying Reflectance [Articolo su rivista]
W., Matusik; B., Ajdin; J., Gu; J., Lawrence; H. P., Lensch; Pellacini, Fabio; S., Rusinkiewicz
abstract

2009 - SubEdit: A Representation for Editing Measured Heterogenous Subsurface Scattering [Articolo su rivista]
Y., Song; X., Tong; Pellacini, Fabio; P., Peers
abstract

2009 - Toward Evaluating Lighting Design Interface Paradigms for Novice Users [Articolo su rivista]
W. B., Kerr; Pellacini, Fabio
abstract

2008 - AppProp: All-Pairs Appearance-Space Edit Propagation [Articolo su rivista]
X., An; Pellacini, Fabio
abstract

We present an intuitive and efficient method for editing the appearance of complex spatially-varying datasets, such as images and measured materials. In our framework, users specify rough adjustments that are refined interactively by enforcing the policy that similar edits are applied to spatially-close regions of similar appearance. Rather than proposing a specific user interface, our method allows artists to quickly and imprecisely specify the initial edits with any method or workflow they feel most comfortable with. An energy optimization formulation is used to propagate the initial rough adjustments to the final refined ones by enforcing the editing policy over all pairs of points in the dataset. We show that this formulation is equivalent to solving a large linear system defined by a dense matrix. We derive an approximate algorithm to compute such a solution interactively by taking advantage of the inherent structure of the matrix. We demonstrate our approach by editing images, HDR radiance maps, and measured materials. Finally, we show that our framework generalizes prior methods while providing significant improvements in generality, robustness and efficiency.

2008 - Backhoe, a Packet Trace and Log Browser [Relazione in Atti di Convegno]
S., Bratus; A., Hansen; Pellacini, Fabio; A., Shubina
abstract

2008 - Eye tracking and online search: Lessons learned and challenges ahead [Articolo su rivista]
Lori, Lorigo; Maya, Haridasan; Hronn, Brynjarsdottir; Ling, Xia; Thorsten, Joachims; Geri, Gay; Laura, Granka; Pellacini, Fabio; Bing, Pan
abstract

2008 - Fast, Realistic Lighting and Material Design using Nonlinear Cut Approximation [Articolo su rivista]
E., Cheslack Postava; R., Wang; O., Akerlund; Pellacini, Fabio
abstract

2008 - Hybrid Hardware-Accelerated Relighting System for Computer Cinematography [Brevetto]
Pellacini, Fabio; K., Vidimče; A., Mohr
abstract

2008 - Tensor Clustering for Rendering Many-Light Animations [Articolo su rivista]
Milos, Hasan; Edgar Velázquez, Armendáriz; Pellacini, Fabio; Kavita, Bala
abstract

2008 - iCheat: A Representation for Artistic Control of Indirect Cinematic Lighting [Articolo su rivista]
Juraj, Obert; J., Krivanek; Pellacini, Fabio; Daniel, Sykora; Sumanta, Pattanaik
abstract

2007 - AppWand: Editing Measured Materials using Appearance-Driven Optimization [Articolo su rivista]
Pellacini, Fabio; J., Lawrence
abstract

2007 - Frequency and structure of long distance scholarly collaborations in a physics community [Articolo su rivista]
Lori, Lorigo; Pellacini, Fabio
abstract

2007 - Interactive Cinematic Relighting with Global Illumination [Capitolo/Saggio]
Pellacini, Fabio; M., Hašan; K., Bala
abstract

2007 - Lighting with paint [Articolo su rivista]
Pellacini, Fabio; F., Battaglia; R. K., Morley; A., Finkelstein
abstract

2007 - Matrix Row-Column Sampling for the Many-Light Problem [Articolo su rivista]
M., Hašan; Pellacini, Fabio; K., Bala
abstract

2006 - Direct-to-indirect transfer for cinematic relighting [Articolo su rivista]
Milos, Hasan; Pellacini, Fabio; Kavita, Bala
abstract

This paper presents an interactive GPU-based system for cinematic relighting with multiple-bounce indirect illumination from a fixed view-point. We use a deep frame-buffer containing a set of view samples, whose indirect illumination is recomputed from the direct illumination on a large set of gather samples, distributed around the scene. This direct-to-indirect transfer is a linear transform which is particularly large, given the size of the view and gather sets. This makes it hard to precompute, store and multiply with. We address this problem by representing the transform as a set of sparse matrices encoded in wavelet space. A hierarchical construction is used to impose a wavelet basis on the unstructured gather cloud, and an image-based approach is used to map the sparse matrix computations to the GPU. We precompute the transfer matrices using a hierarchical algorithm and a variation of photon mapping in less than three hours on one processor. We achieve high-quality indirect illumination at 10-20 frames per second for complex scenes with over 2 million polygons, with diffuse and glossy materials, and arbitrary direct lighting models (expressed using shaders). We compute per-pixel indirect illumination without the need of irradiance caching or other subsampling techniques.

2005 - A Hybrid Monte Carlo Method for Accurate and Efficient Subsurface Scattering [Relazione in Atti di Convegno]
H., Li; Pellacini, Fabio; K. E., Torrance
abstract

2005 - Lpics: a Hybrid Hardware-Accelerated Relighting Engine for Computer Cinematography [Articolo su rivista]
Pellacini, Fabio; Kiril, Vidimce; Aaron, Lefohn; Alex, Mohr; Mark, Leone; John, Warren
abstract

2005 - User-configurable automatic shader simplification [Articolo su rivista]
Pellacini, Fabio
abstract

2004 - Cinematic Lighting [Capitolo/Saggio]
Pellacini, Fabio; K., Vidimče
abstract

2004 - Shadow Map Antialiasing [Capitolo/Saggio]
M., Bunnel; Pellacini, Fabio
abstract

2003 - Functional Difference Predictors (FDPs): Measuring Meaningful Image Differences [Relazione in Atti di Convegno]
Pellacini, Fabio; J. A., Ferwerda
abstract

2003 - Perceptually-driven decision theory for interactive realistic rendering [Articolo su rivista]
Reynald, Dumont; Pellacini, Fabio; James A., Ferwerda
abstract

2002 - A User Interface for Interactive Cinematic Shadow Design [Articolo su rivista]
Pellacini, Fabio; Parag, Tole; Donald P., Greenberg
abstract

2002 - Interactive Global Illumination in Dynamic Scenes [Articolo su rivista]
Parag, Tole; Pellacini, Fabio; B., Walter; Donald P., Greenberg
abstract

2002 - Jigsaw Image Mosaics [Articolo su rivista]
J., Kim; Pellacini, Fabio
abstract

2001 - A Perceptually-Based Texture Caching Algorithm for Hardware-Based Rendering [Relazione in Atti di Convegno]
R., Dumont; Pellacini, Fabio; J. A., Ferwerda
abstract

2001 - A Psychophysically-Based Model of Surface Gloss Perception [Relazione in Atti di Convegno]
J. A., Ferwerda; Pellacini, Fabio; D. P., Greenberg
abstract

2000 - Toward a Psychophysically-Based Light Reflection Model for Image Synthesis [Relazione in Atti di Convegno]
Pellacini, Fabio; James A., Ferwerda; Donald P., Greenberg
abstract

1997 - Influence of growth and preparation condition on the reconstruction of SiC(001) surfaces: a first principles study [Relazione in Atti di Convegno]
A., Catellani; G., Galli; F., Gygi; Pellacini, Fabio
abstract

1997 - Reconstruction and thermal stability of cubic SiC(001) surfaces [Relazione in Atti di Convegno]
A., Catellani; G., Galli; F., Gygi; Pellacini, Fabio
abstract

1997 - Reconstruction and thermal stability of cubic SiC(001) surfaces [Relazione in Atti di Convegno]
A., Catellani; G., Galli; F., Gygi; Pellacini, Fabio
abstract

1997 - STM images of ab-initio molecular dynamics simulated cubic SiC(001) surfaces [Relazione in Atti di Convegno]
Pellacini, Fabio; A., Catellani; G., Galli; F., Gygi
abstract