Browsing by Author "Pellacini, Fabio"

Now showing 1 - 7 of 7
  • No Thumbnail Available
    Item
    3D City Reconstruction from OpenStreetMap Data
    (The Eurographics Association, 2021) Kaszuba, Sara; Pellacini, Fabio; Frosini, Patrizio and Giorgi, Daniela and Melzi, Simone and Rodolà, Emanuele
    Virtual city generation from real data is far from being straightforward for users, as it strictly depends on the application domain, amount of information available, and the adopted reconstruction techniques. Nowadays, reconstruction of virtual cities is of interests in entertainment, urban planning, emergency response and machine learning. To serve these applications, we have developed an open-source tool that can reconstruct cities at scale directly from OpenStreetMap data, that can perform full city generation in the order of hundreds of seconds.
  • No Thumbnail Available
    Item
    Enforcing Energy Preservation in Microfacet Models
    (The Eurographics Association, 2022) Sforza, Davide; Pellacini, Fabio; Cabiddu, Daniela; Schneider, Teseo; Allegra, Dario; Catalano, Chiara Eva; Cherchi, Gianmarco; Scateni, Riccardo
    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.
  • Thumbnail Image
    Item
    EUROGRAPHICS 2019: CGF 38-2 Frontmatter
    (The Eurographics Association and John Wiley & Sons Ltd., 2019) Alliez, Pierre; Pellacini, Fabio; Alliez, Pierre and Pellacini, Fabio
    -
  • Thumbnail Image
    Item
    FloralSurf: Space-Filling Geodesic Ornaments
    (The Eurographics Association, 2023) Albano, Valerio; Fanni, Filippo Andrea; Giachetti, Andrea; Pellacini, Fabio; Ritschel, Tobias; Weidlich, Andrea
    We propose a method to generate floral patterns on manifolds without relying on parametrizations. Taking inspiration from the literature on procedural space-filling vegetation, these patterns are made of non-intersecting ornaments that are grown on the surface by repeatedly adding different types of decorative elements, until the whole surface is covered. Each decorative element is defined by a set of geodesic Bézier splines and a set of growth points from which to continue growing the ornaments. Ornaments are grown in a greedy fashion, one decorative element at a time. At each step, we analyze a set of candidates, and retain the one that maximizes surface coverage, while ensuring that it does not intersect other ornaments. All operations in our method are performed in the intrinsic metric of the surface, thus ensuring that the derived decorations have good coverage, with neither distortions nor discontinuities, and can be grown on complex surfaces. In our method, users control the decorations by selecting the size and shape of the decorative elements and the position of the growth points.We demonstrate decorations that vary in the length of the ornaments' lines, and the number, scale and orientation of the placed decorations. We show that these patterns mimic closely the design of hand-drawn objects. Our algorithm supports any manifold surface represented as triangle meshes. In particular, we demonstrate patterns generated on surfaces with high genus, with and without borders and holes, and that can include a mixture of thin and large features.
  • Thumbnail Image
    Item
    pEt: Direct Manipulation of Differentiable Vector Patterns
    (The Eurographics Association, 2023) Riso, Marzia; Pellacini, Fabio; Ritschel, Tobias; Weidlich, Andrea
    Procedural assets are used in computer graphics applications since variations can be obtained by changing the parameters of the procedural programs. As the number of parameters increases, editing becomes cumbersome as users have to manually navigate a large space of choices. Many methods in the literature have been proposed to estimate parameters from example images, which works well for initial starting points. For precise edits, inverse manipulation approaches let users manipulate the output asset interactively, while the system determines the procedural parameters. In this work, we focus on editing procedural vector patterns, which are collections of vector primitives generated by procedural programs. Recent work has shown how to estimate procedural parameters from example images and sketches, that we complement here by proposing a method for direct manipulation. In our work, users select and interactively transform a set of shape points, while also constraining other selected points. Our method then optimizes for the best pattern parameters using gradient-based optimization of the differentiable procedural functions. We support edits on large variety of patterns with different shapes, symmetries, continuous and discrete parameters, and with or without occlusions.
  • Thumbnail Image
    Item
    pOp: Parameter Optimization of Differentiable Vector Patterns
    (The Eurographics Association and John Wiley & Sons Ltd., 2022) Riso, Marzia; Sforza, Davide; Pellacini, Fabio; Ghosh, Abhijeet; Wei, Li-Yi
    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.
  • No Thumbnail Available
    Item
    Yocto/GL: A Data-Oriented Library For Physically-Based Graphics
    (The Eurographics Association, 2019) Pellacini, Fabio; Nazzaro, Giacomo; Carra, Edoardo; Agus, Marco and Corsini, Massimiliano and Pintus, Ruggero
    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.