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Illuminating Micro Geometry Based on Precomputed Visibility
, 2000
"... ing with credit is permitted. To copy otherwise, to republish, to post on servers, or to redistribute to lists, requires prior specific permission and/or a fee. Request permissions from Publications Dept, ACM Inc., fax +1 (212) 8690481, or permissions@acm.org. Illuminating Micro Geometry Based o ..."
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Cited by 47 (13 self)
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ing with credit is permitted. To copy otherwise, to republish, to post on servers, or to redistribute to lists, requires prior specific permission and/or a fee. Request permissions from Publications Dept, ACM Inc., fax +1 (212) 8690481, or permissions@acm.org. Illuminating Micro Geometry Based on Precomputed Visibility Wolfgang Heidrich # Katja Daubert Jan Kautz HansPeter Seidel MaxPlanckInstitute for Computer Science Abstract Many researchers have been arguing that geometry, bump maps, and BRDFs present a hierarchy of detail that should be exploited for efficient rendering purposes. In practice however, this is often not possible due to inconsistencies in the illumination for these different levels of detail. For example, while bump map rendering often only considers direct illumination and no shadows, geometrybased rendering and BRDFs will mostly also respect shadowing effects, and in many cases even indirect illumination caused by scattered light. In this paper, we pres...
Interactive rendering of trees with shading and shadows
 In Eurographics Workshop on Rendering
, 2001
"... Abstract. The goal of this paper is the interactive rendering of 3D trees covering a landscape, with shading and shadows consistent with the lighting conditions. We propose a new IBR representation, consisting of a hierarchy of Bidirectional Textures, which resemble 6D lightfields. A hierarchy of vi ..."
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Abstract. The goal of this paper is the interactive rendering of 3D trees covering a landscape, with shading and shadows consistent with the lighting conditions. We propose a new IBR representation, consisting of a hierarchy of Bidirectional Textures, which resemble 6D lightfields. A hierarchy of visibility cubemaps is associated to this representation to improve the performance of shadow calculations. An example of hierarchy for a given tree can be a small branch plus its leaves (or needles), a larger branch, and the entire tree. A Bidirectional Texture (BT) provides a billboard image of a shaded object for each pair of view and light directions. We associate a BT for each level of the hierarchy. When rendering, the appropriate level of detail is selected depending on the distance of the tree from the viewpoint. The illumination reaching each level is evaluated using a visibility cubemap. Thus, we very efficiently obtain the shaded rendering of a tree with shadows without loosing details, contrary to mesh simplification methods. We achieved 7 to 20 fps flythroughs of a scene with 1000 trees. Keywords: Realtime rendering, natural scenes, forests, IBR, levels of detail, billboards
Visibility preserving terrain simplification – An experimental study
 In Proc. 18th Annu. ACM Sympos. Comput. Geom
, 2002
"... The terrain surface simplification problem has been studied extensively, as it has important applications in geographic information systems and computer graphics. The goal is to obtain a new surface that is combinatorially as simple as possible, while maintaining a prescribed degree of similarity wi ..."
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The terrain surface simplification problem has been studied extensively, as it has important applications in geographic information systems and computer graphics. The goal is to obtain a new surface that is combinatorially as simple as possible, while maintaining a prescribed degree of similarity with the original input surface. In this paper, we propose new algorithms for simplifying terrain surfaces, designed specifically for a new measure of quality based on preserving interpoint (geodesic) distances. We are motivated by various geographic information system and mapping applications. We have implemented the suggested algorithms and give experimental evidence of their effectiveness in simplifying terrains according to the suggested measure of quality. We experimentally compare their performance with that of another leading simplification method. 1
Approximating the visible region of a point on a terrain
 In Proc. Algorithm Engineering and Experiments (ALENEX’04), accepted
, 2004
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Optimal placement of UVbased communications relay nodes
, 2010
"... We consider a constrained optimization problem with mixed integer and real variables. It models optimal placement of communications relay nodes in the presence of obstacles. This problem is widely encountered, for instance, in robotics, where it is required to survey some target located in one point ..."
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Cited by 3 (3 self)
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We consider a constrained optimization problem with mixed integer and real variables. It models optimal placement of communications relay nodes in the presence of obstacles. This problem is widely encountered, for instance, in robotics, where it is required to survey some target located in one point and convey the gathered information back to a base station located in another point. One or more unmanned aerial or ground vehicles (UAVs or UGVs) can be used for this purpose as communications relays. The decision variables are the number of unmanned vehicles (UVs) and the UV positions. The objective function is assumed to access the placement quality. We suggest one instance of such a function which is more suitable for accessing UAV placement. The constraints are determined by, firstly, a free line of sight requirement for every consecutive pair in the chain and, secondly, a limited communication range. Because of these requirements, our constrained optimization problem is a difficult multiextremal problem for any fixed number of UVs. Moreover, the feasible set of real variables is typically disjoint. We present an approach that allows us to efficiently find a practically acceptable approximation to a global minimum in the problem of optimal placement of communications relay nodes. It is based on a spatial discretization with a subsequent
Rendering Very Large, Very Detailed Terrains
, 2005
"... Usually rendering very large, very detailed terrains has high storage and processing requirements, because huge amounts of data are involved. In this document a new approach to solve the problem of rendering very larger, very detailed terrains is presented. Our proposal is to split the terrain repre ..."
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Usually rendering very large, very detailed terrains has high storage and processing requirements, because huge amounts of data are involved. In this document a new approach to solve the problem of rendering very larger, very detailed terrains is presented. Our proposal is to split the terrain representation into a low detail terrain, which does not required much storage and at runtime extend this low detail terrain with high amounts of details when needed. Our algorithm is based on two existing levelofdetail algorithms presented by Ulrich in [20] and De Boer in [3]. We are using the chunked quadtree structure presented by Ulrich, but the simplification process has been replaced by the scheme presented by De Boer. Together these two algorithms constitutes a simple, efficient levelofdetail algorithm and is suitable for runtime addition of details. The details can be calculated in various ways; we have chosen to use fractals for this purpose. Some techniques to speed up detail calculation is also shown. Details are added to the terrain at runtime by extending the quadtree with new leaf nodes. The value of the height samples in the new nodes are generated as a combination of the calculated details and a subdivision of the existing height samples. The subdivision scheme used is the one presented by Kobbelt in [11]. Results gathered from our implementation of our method shows that storage and memory requirements are low. They also shows that our levelofdetail algorithm is performing very well and renders high quality images. As such, the proposed solution works well; by adding details to an otherwise low detail terrain at runtime makes the terrain appear highly detailed, while storage requirements stays low. Given the high performance of the levelofdetail algorithm, our method is capable of rendering very large, very detailed terrains. i Preface This document presents the results of the midway project conducted by the
Applications of Temporal Coherence in RealTime Rendering
, 2010
"... Realtime rendering imposes the challenging task of creating a new rendering of an input scene at least 60 times a second. Although computer graphics hardware has made staggering advances in terms of speed and freedom of programmability, there still exist a number of algorithms that are too expensiv ..."
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Realtime rendering imposes the challenging task of creating a new rendering of an input scene at least 60 times a second. Although computer graphics hardware has made staggering advances in terms of speed and freedom of programmability, there still exist a number of algorithms that are too expensive to be calculated in this time budget, like exact shadows or an exact global illumination solution. One way to circumvent this hard time limit is to capitalize on temporal coherence to formulate algorithms incremental in time. The main thesis of this work is that temporal coherence is a characteristic of realtime graphics that can be used to redesign wellknown rendering methods to become faster, while exhibiting better visual fidelity. To this end we present our adaptations of algorithms from the fields of exact hard shadows, physically correct soft shadows and fast discrete LOD blending, in which we have successfully incorporated temporal coherence. Additionally, we provide a detailed context of previous work not only in the
Computing the set of all the distant horizons of a terrain
 In Proceedings of the 16th Canadian Conference on Computational Geometry
, 2004
"... We study the problem of computing the set of all distant horizons of a terrain, represented as either: the set of all edges that appear in the set of all distant horizons; the connected sets in the union of all points that appear in the set of all distant horizons (the set of edge fragments); or a s ..."
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We study the problem of computing the set of all distant horizons of a terrain, represented as either: the set of all edges that appear in the set of all distant horizons; the connected sets in the union of all points that appear in the set of all distant horizons (the set of edge fragments); or a search structure to efficiently calculate the edge fragments or edges on a distant horizon from a particular viewing direction. We describe a randomized algorithm that can be used to solve all three forms of the problem with an expected run time of O(n 2+ɛ) for any ɛ> 0 where n is the number of edges in the piecewise linear terrain. We show that solving either of the first two versions of the problem is 3SUM hard, and we also construct a terrain with a single local maxima and a quadratic number of edge fragments in the set of all distant horizons, showing that our solution to the second version of the problem is essentially optimal. 1
An efficient algorithm to compute the viewshed on DEM terrains stored in the external memory
"... Abstract. Nowadays, there is a huge volume of data about terrains available and generally, these data do not fit in the internal memory. So, many GIS applications require efficient algorithms to manipulate the data externally. One of these applications is the viewshed computation that consists in ob ..."
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Abstract. Nowadays, there is a huge volume of data about terrains available and generally, these data do not fit in the internal memory. So, many GIS applications require efficient algorithms to manipulate the data externally. One of these applications is the viewshed computation that consists in obtain the visible points from a given point p. In this paper, we present an efficient algorithm to compute the viewshed on terrains stored in the external memory. The algorithm complexity is O(scan(N)) where N is the number of points in a DEM and scan(N) is the minimum number of I/O operations required to read N contiguous items stored in the external memory. Also, as shown in the results, our algorithm outperforms the known algorithms described in the literature. 1.