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22
Procedural Modeling of Buildings
"... CGA shape, a novel shape grammar for the procedural modeling of CG architecture, produces building shells with high visual quality and geometric detail. It produces extensive architectural models for computer games and movies, at low cost. Context sensitive shape rules allow the user to specify inte ..."
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Cited by 147 (12 self)
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CGA shape, a novel shape grammar for the procedural modeling of CG architecture, produces building shells with high visual quality and geometric detail. It produces extensive architectural models for computer games and movies, at low cost. Context sensitive shape rules allow the user to specify interactions between the entities of the hierarchical shape descriptions. Selected examples demonstrate solutions to previously unsolved modeling problems, especially to consistent mass modeling with volumetric shapes of arbitrary orientation. CGA shape is shown to efficiently generate massive urban models with unprecedented level of detail, with the virtual rebuilding of the archaeological site of Pompeii as a case in point.
Matchmaker: Manifold BReps for nonmanifold rsets
 Proceedings of the ACM Symposium on Solid Modeling
, 1999
"... Many solid modeling construction techniques produce nonmanifold rsets (solids). With each nonmanifold model N we can associate a family of manifold solid models that are infinitely close to N in the geometric sense. For polyhedral solids, each nonmanifold edge of N with 2k incident faces will be ..."
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Cited by 40 (19 self)
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Many solid modeling construction techniques produce nonmanifold rsets (solids). With each nonmanifold model N we can associate a family of manifold solid models that are infinitely close to N in the geometric sense. For polyhedral solids, each nonmanifold edge of N with 2k incident faces will be replicated k times in any manifold model M of that family. Furthermore, some nonmanifold vertices of N must also be replicated in M, possibly several times. M can be obtained by defining, in N, a single adjacent face TA(E,F) for each pair (E,F) that combines an edge E and an incident face F. The adjacency relation satisfies TA(E,TA(E,F))=F. The choice of the map A defines which vertices of N must be replicated in M and how many times. The resulting manifold representation of a nonmanifold solid may be encoded using simpler and more compact datastructures, especially for triangulated model, and leads to simpler and more efficient algorithms, when it is used instead of a nonmanifold repre...
A new paradigm for changing topology during subdivision modeling
 In Proceedings of Pacific Graphics
, 2000
"... In this paper, we present a new paradigm that allows dynamically changing the topology of 2manifold polygonal meshes. Our new paradigm always guarantees topological consistency of polygonal meshes. Based on our paradigm, by simply adding and deleting edges, handles can be created and deleted, holes ..."
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Cited by 11 (4 self)
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In this paper, we present a new paradigm that allows dynamically changing the topology of 2manifold polygonal meshes. Our new paradigm always guarantees topological consistency of polygonal meshes. Based on our paradigm, by simply adding and deleting edges, handles can be created and deleted, holes can be opened or closed, polygonal meshes can be connected or disconnected. These edge insertion and edge deletion operations are highly consistent with subdivision algorithms. In particular, these operations can be easily included into a subdivision modeling system such that the topological changes and subdivision operations can be performed alternatively during model construction. We demonstrate practical examples of topology changes based on this new paradigm and show that the new paradigm is convenient, effective, efficient, and friendly to subdivision surfaces. 1
A Coherent Sweep Plane Slicer for Layered Manufacturing
 In Fifth Symposium on Solid Modeling and Applications
, 1999
"... We describe the design and implementation of a coherent sweep plane slicer, built on top of a topological data structure, which "slices" a tessellated 3D CAD model into horizontal, 2.5D layers of uniform thickness for input to layered manufacturing processes. Previous algorithms for slic ..."
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Cited by 9 (3 self)
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We describe the design and implementation of a coherent sweep plane slicer, built on top of a topological data structure, which "slices" a tessellated 3D CAD model into horizontal, 2.5D layers of uniform thickness for input to layered manufacturing processes. Previous algorithms for slicing a 3D brep into the layers that form the process plan for these machines have treated each slice operation as an individual intersection with a plane, which is needlessly inefficient given the significant coherence between the finely spaced slices. An additional shortcoming of many existing slicers that we address is a lack of robustness when dealing with nonmanifold geometry. Our algorithm exploits both geometric and topological interslice coherence to output clean slices with explicit nesting of contours. Keywords: rapid prototyping, computational geometry, topology, slicing, .STL format, CAD/CAM 1 Introduction Designers who want to make prototypes of solid threedimensional parts directly ...
Reconstruction of curved solids from engineering drawings
 COMPUTERAIDED DESIGN
, 2001
"... This paper presents a new approach for reconstructing solids with planar, quadric and toroidal surfaces from threeview engineering drawings. By applying geometric theory to 3D reconstruction, our method is able to remove restrictions placed on the axes of curved surfaces by existing methods. The m ..."
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Cited by 8 (0 self)
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This paper presents a new approach for reconstructing solids with planar, quadric and toroidal surfaces from threeview engineering drawings. By applying geometric theory to 3D reconstruction, our method is able to remove restrictions placed on the axes of curved surfaces by existing methods. The main feature of our algorithm is that it combines the geometric properties of conics with af®ne properties to recover a wider range of 3D edges. First, the algorithm determines the type of each 3D candidate conic edge based on its projections in three orthographic views, and then generates that candidate edge using the conjugate diameter method. This step produces a wireframe model that contains all candidate vertices and candidate edges. Next, a maximum turning angle method is developed to ®nd all the candidate faces in the wireframe model. Finally, a general and efficient searching technique is proposed for ®nding valid solids from the candidate faces; the technique greatly reduces the searching space and the backtracking incidents. Several examples are given to demonstrate the efficiency and
Blist: A Boolean list formulation of CSG trees
, 1998
"... Set membership classification algorithms visit nodes of a CSG tree through a recursive divideandconquer process, which stores intermediate results in a stack, whose depth equals the height, H, of the tree. During this process, the candidate sets is usually subdivided into uniform cells, whose inte ..."
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Cited by 8 (2 self)
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Set membership classification algorithms visit nodes of a CSG tree through a recursive divideandconquer process, which stores intermediate results in a stack, whose depth equals the height, H, of the tree. During this process, the candidate sets is usually subdivided into uniform cells, whose interior is disjoint from primitives' boundaries. Cells inside the CSG object are identified by combining the binary results of classifying them against the primitives. In parallel systems, which allocate a different process to each leaf of the tree, and in algorithms that classify large collections of regularly spaced candidate sets (points, pixels, voxels, rays, or crosssections) against the primitives using forward differences, a separate stack is associated with each candidate or cell. Our new representation for CSG trees, called Blist, distributes the merging operation to the primitives and reduces the storage requirement for each cell to log(H+1) bits. Blist can represent any Boolean expr...
Geometric Algorithms and Data Representation for Solid Freeform Fabrication
, 2000
"... Solid freeform fabrication (SFF) refers to a class of technologies used for making rapid prototypes of 3D parts. With these processes, a triangulated boundary representation of the CAD model of the part is "sliced" into horizontal 2.5D layers of uniform thickness that are successively ..."
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Cited by 8 (0 self)
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Solid freeform fabrication (SFF) refers to a class of technologies used for making rapid prototypes of 3D parts. With these processes, a triangulated boundary representation of the CAD model of the part is "sliced" into horizontal 2.5D layers of uniform thickness that are successively deposited, hardened, fused, or cut, depending on the particular process, and attached to the layer beneath. The stacked layers form the final part. The current de facto standard interface to these machines, STL, has many shortcomings. We have developed a new "Solid Interchange Format" (SIF) for use as a digital interface to SFF machines. SIF includes constructs for specifying surface and volume properties, precision information, and transmitting unevaluated Boolean trees. We have also develope...
TopologyAdaptive Mesh Deformation for Surface Evolution, Morphing, and MultiView Reconstruction
, 2009
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BOOLE: A Boundary Evaluation System for Boolean Combinations of Sculptured Solids
, 2000
"... In this paper we describe a system, BOOLE, that generates the boundary representations (Breps) of solids given as a CSG expression in the form of trimmed B'ezier patches. The system makes use of techniques from computational geometry, numerical linear algebra and symbolic computation to gen ..."
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Cited by 6 (2 self)
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In this paper we describe a system, BOOLE, that generates the boundary representations (Breps) of solids given as a CSG expression in the form of trimmed B'ezier patches. The system makes use of techniques from computational geometry, numerical linear algebra and symbolic computation to generate the Breps. Given two solids, the system first computes the intersection curve between the two solids using our surface intersection algorithm. Using the topological information of each solid, it computes various components within each solid generated by the intersection curve and their connectivity. The component classification step is performed by rayshooting. Depending on the Boolean operation performed, appropriate components are put together to obtain the final solid. We also present techniques to parallelize this system on shared memory multiprocessor machines. The system has been successfully used to generate Breps for a number of large industrial models including parts of ...