Bounding Volume Hierarchy Research Articles

Wavefront tracing for undersea acoustic propagation

An acoustic wavefront tracing algorithm and corresponding computational implementation is presented. Similar to ray tracing and beam tracing, wavefront tracing casts independent rays that refract through the medium and reflect from boundaries. However, with wavefront tracing these rays step congruously and are connected as a triangulated surface. As this triangulated surface moves through space and time it contacts boundaries, receivers, or other points of interest, thereby providing all possible paths from the source. As each triangle steps forward, three space-filling tetrahedra are formed and acoustic properties are then linearly interpolated via barycentric coordinates. This interpolation also applies at a boundary surface, allowing for both specular reflection and diffuse scattering. The algorithm is derived from the wavefront construction method, in which the triangulated surface is adaptively modified to maintain a desired level of detail. However, by keeping the wavefront topology fixed, along with an efficient encoding of the algorithm, highly detailed simulations with millions of triangles are achievable. Borrowing from the computer graphics community, a bounding volume hierarchy is used to accelerate the computation of ray–boundary intersections. An example simulation of a synthetic aperture sonar ping is provided, in which the wavefront comprises 21 million triangles and a rippled seafloor comprises five hundred thousand triangles.

Hardware-Accelerated Dual-Split Trees

Bounding volume hierarchies (BVH) are the most widely used acceleration structures for ray tracing due to their high construction and traversal performance. However, the bounding planes shared between parent and children bounding boxes is an inherent storage redundancy that limits further improvement in performance due to the memory cost of reading these redundant planes. Dual-split trees can create identical space partitioning as BVHs, but in a compact form using less memory by eliminating the redundancies of the BVH structure representation. This reduction in memory storage and data movement translates to faster ray traversal and better energy efficiency. Yet, the performance benefits of dual-split trees are undermined by the processing required to extract the necessary information from their compact representation. This involves bit manipulations and branching instructions which are inefficient in software. We introduce hardware acceleration for dual-split trees and show that the performance advantages over BVHs are emphasized in a hardware ray tracing context that can take advantage of such acceleration. We provide details on how the operations needed for decoding dual-split tree nodes can be implemented in hardware and present experiments in a number of scenes with different sizes using path tracing. In our experiments, we have observed up to 31% reduction in render time and 38% energy saving using dual-split trees as compared to binary BVHs representing identical space partitioning.

Using Hardware Ray Transforms to Accelerate Ray/Primitive Intersections for Long, Thin Primitive Types

With the recent addition of hardware ray tracing capabilities, GPUs have become incredibly efficient at ray tracing both triangular geometry, and instances thereof. However, the bounding volume hierarchies that current ray tracing hardware relies on are known to struggle with long, thin primitives like cylinders and curves, because the axis-aligned bounding boxes that these hierarchies rely on cannot tightly bound such primitives. In this paper, we evaluate the use of RTX ray tracing capabilities to accelerate these primitives by tricking the GPU's instancing units into executing a hardware-accelerated oriented bounding box (OBB) rejection test before calling the user's intersection program. We show that this can be done with minimal changes to the intersection programs and demonstrate speedups of up to 5.9× on a variety of data sets.

OLBVH: octree linear bounding volume hierarchy for volumetric meshes

We present a novel bounding volume hierarchy for GPU-accelerated direct volume rendering (DVR) as well as volumetric mesh slicing and inside-outside intersection testing. Our novel octree-based data structure is laid out linearly in memory using space filling Morton curves. As our new data structure results in tightly fitting bounding volumes, boundary markers can be associated with nodes in the hierarchy. These markers can be used to speed up all three use cases that we examine. In addition, our data structure is memory-efficient, reducing memory consumption by up to 75%. Tree depth and memory consumption can be controlled using a parameterized heuristic during construction. This allows for significantly shorter construction times compared to the state of the art. For GPU-accelerated DVR, we achieve performance gain of 8.4times –13times . For 3D printing, we present an efficient conservative slicing method that results in a 3times –25times speedup when using our data structure. Furthermore, we improve volumetric mesh intersection testing speed by 5times –52times .

Enhancing the dissipative properties of particle dampers using rigid obstacle-grids

Particle dampers (PDs) are becoming a popular alternative to conventional damping devices due to their simple design and their ability to dissipate energy over a wide frequency range. The energy dissipation in PDs takes place due to relative motion between solid particles within the PD enclosure. The degree of relative motion depends on various parameters, especially it is highly sensitive to vibration amplitude changes. Usually, the particle size is much smaller than that of the PD enclosure which, under low forcing conditions, leads to sub-optimal momentum transfer and thereby leads to lower energy dissipation. In this work a new approach is investigated, in which a complex 3D rigid obstacle-grid is deliberately introduced inside the PD enclosure in order to overcome the shortcomings of a conventional PD. In order to better understand the influence of various dissipation mechanisms, simulations were performed. The Discrete Element Method (DEM) is used to model the interactions between the solid particles and their surroundings. In the simulations, the rigid obstacle-grid is described using a triangular surface mesh and to speed-up the collision detection process, efficient bounding volume hierarchy data structures were used. Moreover, laboratory experiments were set up to test the validity of the simulation models. The experimental setup consists of an electromagnetic shaker used to excite, via elastic elements, a clamped beam on which a PD with a rigid obstacle-grid is mounted. The obstacle-grid used in the experiments is manufactured using a Stereolithography 3D printer. Simulations and experiments were observed to be in good agreement. Moreover, the damping performance of a PD with a rigid obstacle-grid is observed to be at least twice as good as a conventional PD. Visual observations indicate that particles which would have otherwise been hardly contributing to energy dissipation, move violently due to an obstacle-grid, and hence actively participate in the energy dissipation process. Furthermore, a numerical study indicates that the obstacle-grid cell-size has a profound effect on the dissipation, allowing it to be used as an additional parameter to tune the damping performance of PDs.

Surface–Surface-Intersection Computation Using a Bounding Volume Hierarchy with Osculating Toroidal Patches in the Leaf Nodes

We present an efficient and robust algorithm for computing the intersection curve of two freeform surfaces using a Bounding Volume Hierarchy (BVH), where the leaf nodes contain osculating toroidal patches. The covering of each surface by a union of tightly fitting toroidal patches greatly simplifies the geometric operations involved in the surface–surface-intersection computation, i.e., the bounding of surface normals, the detection of surface binormals, the point projection from one surface to the other surface, and the intersection of local surface patches. Moreover, the hierarchy of simple bounding volumes (such as rectangle-swept spheres) accelerates the geometric search for the potential pairs of surface patches that may generate some curve segments in the surface–surface-intersection. We demonstrate the effectiveness of our approach by using test examples of intersecting two freeform surfaces, including some highly non-trivial examples with tangential intersections. In particular, we test the intersection of two almost identical surfaces, where one surface is obtained from the same surface, using a rotation around a normal line by a smaller and smaller angle θ=10−k degree, k=0,…,5. The intersection results are often given as surface subpatches in some highly tangential areas, and even as the whole surface itself, when θ=0.00001∘.

Binary Ostensibly‐Implicit Trees for Fast Collision Detection

AbstractWe present a simple, efficient and low‐memory technique, targeting fast construction of bounding volume hierarchies (BVH) for broad‐phase collision detection. To achieve this, we devise a novel representation of BVH trees in memory. We develop a mapping of the implicit index representation to compact memory locations, based on simple bit‐shifts, to then construct and evaluate bounding volume test trees (BVTT) during collision detection with real‐time performance. We model the topology of the BVH tree implicitly as binary encodings which allows us to determine the nodes missing from a complete binary tree using the binary representation of the number of missing nodes. The simplicity of our technique allows for fast hierarchy construction achieving over 6× speedup over the state‐of‐the‐art. Making use of these characteristics, we show that not only it is feasible to rebuild the BVH at every frame, but that using our technique, it is actually faster than refitting and more memory efficient.

Efficient Minimum Distance Computation for Solids of Revolution

AbstractWe present a highly efficient algorithm for computing the minimum distance between two solids of revolution, each of which is defined by a planar cross‐section region and a rotation axis. The boundary profile curve for the cross‐section is first approximated by a bounding volume hierarchy (BVH) of fat arcs. By rotating the fat arcs around the axis, we generate the BVH of fat tori that bounds the surface of revolution. The minimum distance between two solids of revolution is then computed very efficiently using the distance between fat tori, which can be boiled down to the minimum distance computation for circles in the three‐dimensional space. Our circle‐based approach to the solids of revolution has distinctive features of geometric simplification. The main advantage is in the effectiveness of our approach in handling the complex cases where the minimum distance is obtained in non‐convex regions of the solids under consideration. Though we are dealing with a geometric problem for solids, the algorithm actually works in a computational style similar to that of handling planar curves. Compared with conventional BVH‐based methods, our algorithm demonstrates outperformance in computing speed, often 10–100 times faster. Moreover, the minimum distance can be computed very efficiently for the solids of revolution under deformation, where the dynamic reconstruction of fat arcs dominates the overall computation time and takes a few milliseconds.

Fast spacecraft solar radiation pressure modeling by ray tracing on graphics processing unit

A novel method is presented to evaluate on the graphics processing unit (GPU) the force and torque on a spacecraft due to solar radiation pressure. The method employs efficient ray tracing techniques, developed in the graphics rendering discipline, to resolve spacecraft self-shadowing and reflections at faster than real-time computation speed. The primary algorithmic components of the ray tracing process which contribute to the method’s computational efficiency are described. These components include two-level bounding volume hierarchy acceleration data structures, fast ray to bounding box intersection testing using the slab intersection algorithm and fast triangle intersection testing using the Möller-Trumbore algorithm. Spacecraft material optical properties are represented as a combination of Lambertian diffuse and ideal specular reflections. Both diffuse and specular ray-surface interactions are modeled. The approach is implemented using C++ and OpenCL and executed on a consumer grade GPU. Model validation is presented comparing ray traced force and torque values to the same quantities produce by a faceted analytic model. Numerical results illustrate the impact of self-shadowing on the force and torque calculation, and demonstrate the fast computational speed that is enabled with this implementation.

Hybrid Scene Structuring for Accelerating 3D Radiative Transfer Simulations

Three-dimensional (3D) radiative transfer models are the most accurate remote sensing models. However, presently the application of 3D models to heterogeneous Earth scenes is a computationally intensive task. A common approach to reduce computation time is abstracting the landscape elements into simpler geometries (e.g., ellipsoid), which, however, may introduce biases. Here, a hybrid scene structuring approach is proposed to accelerate the radiative transfer simulations while keeping the scene as realistic as possible. In a first step, a 3D description of the Earth landscape with equal-sized voxels is optimized to keep only non-empty voxels (i.e., voxels that contain triangles) and managed using a bounding volume hierarchy (BVH). For any voxel that contains triangles, within-voxel BVHs are created to accelerate the ray–triangle intersection tests. The hybrid scheme is implemented in the Discrete Anisotropic Radiative Transfer (DART) model by integrating the Embree ray-tracing kernels developed at Intel. In this paper, the performance of the hybrid algorithm is compared with the original uniform grid approach implemented in DART for a 3D city scene and a forest scene. Results show that the removal of empty voxels can accelerate urban simulation by 1.4×~3.7×, and that the within-voxel BVH can accelerate forest simulations by up to 258.5×.

DESIGN AND APPLICATION OF BOUNDING VOLUME HIERARCHY COLLISION DETECTION ALGORITHM BASED ON VIRTUAL SPHERE

The result of collision detection is closely related to the further deformation or cutting action of soft tissue. In order to further improve the efficiency and stability of collision detection, in this paper, a collision detection algorithm of bounding volume hierarchy based on virtual sphere was proposed. The proposed algorithm was validated and the results show that the detection efficiency of the bounding volume hierarchy algorithm based on virtual sphere is higher than that of the serial hybrid bounding volume hierarchy algorithm and the parallel hybrid bounding volume hierarchy algorithm. Different collision detection algorithms were tested and the results show that the collision detection algorithm based on virtual sphere has high detection efficiency and good stability. As the number of triangular patches increased, the advantage was more and more obvious. Finally, the proposed algorithm was applied to two large and medium-sized virtual scenes to implement the collision detection between the vastus lateralis muscle, thigh and surgical instrument. Based on the virtual sphere, the collision detection algorithm of bounding volume hierarchy can implement efficient and stable collision detection in a virtual surgery system. Meanwhile, the algorithm can be combined with other acceleration algorithms (such as the multithread acceleration algorithm) to further improve detection efficiency.

Fast collision detection between high resolution polygonal models

In this paper, we address the problem of collision detection between very high resolution polygonal models. We propose an approach that uses the EBP-Octree data structure in a single-core CPU architecture. The algorithm manages a set of files to support a cache-like out-of-core algorithm that performs the collision and intersection tests. Our method uses a data structure called EBP-Octree (Extended Bounding-Planes Octree), which is a very tight hierarchy of convex bounding volumes that, based on a spatial decomposition of the model using an octree, defines a bounding volume at each node by a subset of the planes of the portion of polygonal model contained at that node. The system adapts the memory consumption to the system’s hardware features so it can provide exact triangle collision detection in almost any environment, since the amount of information in the main memory can be limited just varying the threshold of the EBP-Octree. We have tested the data structure and the algorithm in scenarios where two models of 28 million polygons move through one another, achieving real time frame rates for first collision tests on a commonly available computer.

Ray Classification for Accelerated BVH Traversal

AbstractFor ray tracing based methods, traversing a hierarchical acceleration data structure takes up a substantial portion of the total rendering time. We propose an additional data structure which cuts off large parts of the hierarchical traversal. We use the idea of ray classification combined with the hierarchical scene representation provided by a bounding volume hierarchy. We precompute short arrays of indices to subtrees inside the hierarchy and use them to initiate the traversal for a given ray class. This arrangement is compact enough to be cache‐friendly, preventing the method from negating its traversal gains by excessive memory traffic. The method is easy to use with existing renderers which we demonstrate by integrating it to the PBRT renderer. The proposed technique reduces the number of traversal steps by 42% on average, saving around 15% of time of finding ray‐scene intersection on average.

Holistic clash detection improvement using a component dependent network in BIM projects

Abstract Building information modeling (BIM) has been increasingly used for design coordination, and clash detection is one important application. However, some studies argued that BIM-enabled clash detection contains many irrelevant clashes. This paper proposes to use network analysis to improve clash detection from a holistic view because a building is an inseparable whole and the dependency relations between building components influence the impacts of clashes. A building component network centered on clash objects is built to represent component dependency. To build the network, this paper determines three kinds of spatial dependent: clash, impact, and connection. For clash relations, the paper further distinguishes four types: intersection, penetration, penetration through, and containment based on the intersection curves of clash objects. To improve generality, Industry Foundation Classes (IFC) models are used to query geometric information and bounding volume hierarchy (BVH) structures are used to eliminate irrelevant comparison for expediting the query process. The paper tests the network method on a real project for improving clash detection and confirms that the method helps to identify irrelevant clashes in four scenarios and reduces 17% of irrelevant clashes. In addition, the paper uses the network to automatically group relevant clashes, thereby decreasing >50% of the clashes initially reported. The paper also shows the function of the component dependent network to analyze the surrounding environment of clashes and identify central components for supporting clash correction.

Quantized bounding volume hierarchies for neighbor search in molecular simulations on graphics processing units

We present an algorithm for neighbor search in molecular simulations on graphics processing units (GPUs) based on bounding volume hierarchies (BVHs). The BVH is compressed into a low-precision, quantized representation to increase the BVH traversal speed compared to a previous implementation. We find that neighbor search using the quantized BVH is roughly two to four times faster than current state-of-the-art methods using uniform grids (cell lists) for a suite of benchmarks for common molecular simulation models. Based on the benchmark results, we recommend using the BVH instead of a single cell list for neighbor list generation in molecular simulations on GPUs.

Automatic contact detection between rope fibers

Understanding and modeling contact behavior of rope-like structures imposed by pure torsion represents a very difficult topic among the non-smooth mechanical problems. Apart from the high non-linearities on the boundary conditions, the location of real contact areas between inter fibers becomes a prerequisite difficulty. In this paper, a new three-stages contact searching algorithm based on bounding volume hierarchies and orthogonal projections is developed for fiber contact problems involving large deformation. In particular, an improved axis aligned bounding boxes hierarchy based on the specific geometry component is proposed, which can directly result in vertex-element pairs. The frictional contact forces are solved in a reduced system within the bi-potential framework. The algorithms are implemented into the in-house finite element software FER/Impact and some numerical examples are carried out to illustrate the proposed methods.

Bi-potential and co-rotational formulations applied for real time simulation involving friction and large deformation

This paper concerns mainly numerical aspects for the real-time manipulation of deformable objects in the context of virtual surgery. The bi-potential method in the form of augmented Lagrangian is extended to solve multiple contact problems within real time computing requirements. Nonlinearities of large deformation are also included to describe the mechanical behavior of soft tissues. To obtain both accuracy and realism, the approximated co-rotational finite element method is applied to make a compromise between accuracy and computational cost. It is difficult to detect collisions between virtual objects at interactive rates. In this work, we use an optimal bounding volume hierarchy technique to acquire a good detecting efficiency. Two numerical examples are carried out to illustrate the efficiency, robustness and accuracy of the presented approaches.

Parallel BVH Construction Using Locally Density Clustering

A novel bounding volume hierarchy (BVH) construction method based on locally dense clustering (LDC) was proposed for the low quality of BVH constructed in a complex scene with uneven distribution of primitives. The quality of the BVH was effectively improved by defining primitive density, analyzing the relation between density and traversal efficiency, selecting primitives with high density as the clustering center at the early stages of construction, and combining with top-down iterative clustering and bottom-up agglomerative clustering (AC). In order to effectively calculate primitive density, a local search strategy based on Morton coding was adopted. This strategy can quickly get approximate primitive density information through GPU. We evaluate the method and show that, in the complex building scene with uneven distribution of primitives, our method is 13% higher in traversal speed and 11% lower in surface area heuristic (SAH) cost. That means our method can improve the rendering speed of ray tracing effectively.

Importance Sampling of Many Lights with Adaptive Tree Splitting

We present a technique to importance sample large collections of lights (including mesh lights as collections of small emitters) in the context of Monte-Carlo path tracing. A bounding volume hierarchy over all emitters is traversed at each shading point using a single random number in a way that importance samples their predicted contribution. The tree aggregates energy, spatial and orientation information from the emitters to enable accurate prediction of the effect of a cluster of lights on any given shading point. We further improve the performance of the algorithm by forcing splitting until the importance of a cluster is sufficiently representative of its contents.

Hierarchical Visibility for Virtual Reality

We introduce a novel primary visibility algorithm based on ray casting that provides real time performance and a feature set well suited for rendering virtual reality. The flexibility provided by our approach allows for a variety of features such as lens distortion, sub-pixel rendering, very wide field of view, foveation and stochastic depth of field blur to be implemented and composed naturally while maintaining real time performance. In contrast, the current rasterization pipelines implemented in hardware require multiple passes and/or post processing to approximate these features and current highly optimized ray tracers, which primarily focus on Monte Carlo path tracing, do not achieve real time performance on current VR displays (1080x1200x2@90hz). Our approach uses a bounding volume hierarchy acceleration and a two level frustum culling/entry point search algorithm to optimize the traversal of coherent primary visibility rays. We introduce an adaptation of MSAA for raycasting that significantly lowers memory bandwidth, we leverage an AVX optimized CPU traversal to perform the majority of culling and an optimized CUDA GPU implementation for triangle intersection, multi-sample antialiasing, and shading. The implementation provides support for animation and physically-based shading and lighting. We believe this approach presents a concrete, viable alternative to rasterization that is significantly better suited to rendering for virtual and augmented reality. In order to engage the community, we have released our implementation under an open-source license.