Fast swept-volume distance for robust collision detection

Purpose: Modern radiotherapy increasingly employs large immobilization devices, gantry attachments, and couch rotations for treatments. All of which raise the risk of collisions between the patient and the gantry / couch. Collision detection is often achieved by manually checking each couch position in the treatment room and sometimes results in extraneous imaging if collisions are detected after image based setup has begun. In the interest of improving efficiency and avoiding extra imaging, we explore the use of a surface imaging based collision detection model. Methods: Surfaces acquired from AlignRT (VisionRT, London, UK) were transferred in wavefront format to a custom Matlab (Mathworks, Natick, MA) software package (CCHECK). Computed tomography (CT) scans acquired at the same time were sent to CCHECK in DICOM format. In CCHECK, binary maps of the surfaces were created and overlaid on the CT images based on the fixed relationship of the AlignRT and CT coordinate systems. Isocenters were added through a graphical user interface (GUI). CCHECK then compares the inputted surfaces to a model of the linear accelerator (linac) to check for collisions at defined gantry and couch positions. Note, CCHECK may be used with or without a CT. Results: The nominal surface image field of view is 650 mm × 900 mm, with variance based on patient position and size. The accuracy of collision detections is primarily based on the linac model and the surface mapping process. The current linac model and mapping process yield detection accuracies on the order of 5 mm, assuming no change in patient posture between surface acquisition and treatment. Conclusions: CCHECK provides a non-ionizing method to check for collisions without the patient in the treatment room. Collision detection accuracy may be improved with more robust linac modeling. Additional gantry attachments (e.g. conical collimators) can be easily added to the model.

<p>Modern computing technology enters the era of parallel computing with the trend of sustainable and scalable parallelism. Single Instruction Multiple Data (SIMD) is an important way to go along with the trend. It is able to gather more and more computing ability by increasing the number of processor cores without the need of modifying the program. Meanwhile, in the field of scientific computing and engineering design, many computation intensive applications are facing the challenge of increasingly large amount of data. Data parallel computing will be an important way to further improve the performance of these applications. In this paper, we take the accurate collision detection in building information modeling as an example. We demonstrate a model for constructing a data parallel algorithm. According to the model, a complex object is decomposed into the sets of simple objects; collision detection among complex objects is converted into those among simple objects. The resulting algorithm is a typical SIMD algorithm, and its advantages in parallelism and scalability is unparalleled in respect to the traditional algorithms.</p>

An algorithm of two stages collision detection is presented for moving objectives in virtual scene. Firstly, AABB bounding box was used to test the intersection of interesting objects in coarse detection stage. Then combining space projection with Z-buffer algorithm, the potential intersecting objects in previous step were tested in precision detection stage, thus we can obtain objects collision data information and complete object collision detection. Finally experimental results show that the algorithm is more efficiency than traditional bounding box detection, the improved technology can realize further accurate collision detection.

Performing accurate and precise collision detection method between objects in virtual environment application such as computer games and medical simulation is important in computer graphics research and development. Given pair of objects that near colliding, numerous mechanic has been developed by researchers in order to minimize computation time and increase accuracy of the detection. However, most of these techniques required a lot of computational cost, extra processing power and complex algebraic equations just to solve distance between near colliding objects. In this paper, we described an alternate technique, which is a theoretical framework of novel technique in order to find the optimum closest distance between two or more convex polyhedral in virtual environment application. Given pair of near colliding objects, we proposed an easy to implement mechanism using dynamic origin point by creating inner and middle Axis Aligned Bounding-Box just to find closest distance between objects. We believed that the technique is suitable to be used in any game engine tools for computer games and medical simulation.

Collision detection (CD) is easy to implement in baseband coaxial CSMA/CD networks, but is a formidable design challenge in optical fiber implementations. Seven different methods for detecting collisions in fiber optic networks are described and analyzed. Attention is focused on CD accuracy, CD dynamic range, implementation considerations, and reliability issues.

For safe last‐mile autonomous robot delivery services in complex environments, rapid and accurate collision prediction and detection is vital. This study proposes a suitable neural network model that relies on multiple navigation sensors. A light detection and ranging technique is used to measure the relative distances to potential collision obstacles along the robot's path of motion, and an accelerometer is used to detect impacts. The proposed method tightly couples relative distance and acceleration time‐series data in a complementary fashion to minimize errors. A long short‐term memory, fully connected layer, and SoftMax function are integrated to train and classify the rapidly changing collision countermeasure state during robot motion. Simulation results show that the proposed method effectively performs collision prediction and detection for various obstacles.

Virtual reality applications such as computer games form a large portion of the computing industry. The increasing expectations for immersive and interactive entertainment require fast graphics rendering with a lot of details and high-fidelity physics simulation. Interference and collision detection between general polygonal models, including all those tasks in the simulated motion of solids which cannot penetrate one another, has been widely explored. The most recent works have been focused on increasing the number of collision queries per second to an interactive rate, assuming that the computing resources such as memory, CPU capacity, and network bandwidth are sufficient all the time. However, the performance of a collision detection algorithm may vary in real environments where the available computing resources are not sufficient or are dynamic at runtime. Such an unstable performance directly affects the interactive rate of many applications, which is not acceptable. This drawback has been noticed extensively by practitioners. Little research work has been introduced to systematically solve this problem. One way out of this problem is to use a technique to dynamically adjust the cost of the collision detection (CD) task according to the measurements of available resources. In this dissertation, a solution to the problem is proposed. The problem is analyzed under three different physical environments: single low end computer, clustered multiple-machine setting, and distributed environment. An extensive comparative study of several methods is done in the context of polygonal models. A new approach, "multi-resolution collision detection", is proposed. It performs time-critical and exact interference detection on continuous level of detail (LOD) representations of arbitrary triangle meshes undergoing rigid body motion. The goal of this work is to extend the bounding volume hierarchy (BVH) based collision detection approach from static to dynamic in order to adapt the cost of collision detection to the available resource in either centralized or distributed environments. Several adaptive mesh refinement criteria based on viewing distance, application context, and movement velocity are proposed. Global and local mesh refinement algorithms and a BVH CD algorithm are introduced. They are computationally simple and achieve reliable real-time performance. The complexity of the proposed algorithms is analyzed and proved. Measurements are taken to compare with the analytical results and strong agreements are achieved. The major application areas considered are distributed virtual environments (DVEs) and interactive haptic applications.

Purpose – This paper aims to find an objects representation scheme with high precision and to compute the objects’ separation distance effectively in final analysis. Proximity queries have been used widely in robot trajectory planning, automatic assembly planning, virtual surgery and many other applications. The core of proximity query is the precise computation of (minimum) separation distance in narrow phase, and specific object representation scheme corresponds to different methods of separation distance computation. Design/methodology/approach – In this paper, a second-order cone programming (SOCP)-based (minimum) separation distance computation algorithm was proposed. It treats convex superquadrics, descriptive primitives of complex object as the study objects. The separation distance between two convex superquadrics was written as a general nonlinear programming (NLP) problem with superquadric constraints and then transformed into an SOCP problem with the method of conic formulation of superquadric constraints. Finally, a primal-dual interior point method embedded in MOSEK was used for solving the SOCP problem. Findings – The proposed algorithm achieved exact separation distance computation between convex superquadrics, with a relative error of 10-6. It is particularly suitable for proximity queries in narrow phase of static collision detection algorithms. Further, the proposed algorithm achieved continuous collision detection between rectilinear translation superquadrics. Originality/value – The proposed algorithm in narrow phase of static collision detection algorithms makes objects’ separation distance effectively computed. Proximity queries are easy and more accurate to perform in this way.

Background: As commercial motion tracking technology becomes more readily available, it is necessary to evaluate the accuracy of these systems before using them for biomechanical and motor rehabilitation applications. Objective: This study aimed to evaluate the relative position accuracy of the Oculus Touch controllers in a 2.4 x 2.4 m play-space. Methods: Static data samples (n=180) were acquired from the Oculus Touch controllers at step sizes ranging from 5 to 500 mm along 16 different points on the play-space floor with graph paper in the x (width), y (height), and z (depth) directions. The data were compared with reference values using measurements from digital calipers, accurate to 0.01 mm; physical blocks, for which heights were confirmed with digital calipers; and for larger step sizes (300 and 500 mm), a ruler with hatch marks to millimeter units. Results: It was found that the maximum position accuracy error of the system was 3.5 ± 2.5 mm at the largest step size of 500 mm along the z-axis. When normalized to step size, the largest error found was 12.7 ± 9.9% at the smallest step size in the y-axis at 6.23 mm. When the step size was <10 mm in any direction, the relative position accuracy increased considerably to above 2% (approximately 2 mm at maximum). An average noise value of 0.036 mm was determined. A comparison of these values to cited visual, goniometric, and proprioceptive resolutions concludes that this system is viable for tracking upper-limb movements for biomechanical and rehabilitation applications. The accuracy of the system was also compared with accuracy values from previous studies using other commercially available devices and a multicamera, marker-based professional motion tracking system. Conclusions: The study found that the linear position accuracy of the Oculus Touch controllers was within an agreeable range for measuring human kinematics in rehabilitative upper-limb exercise protocols. Further testing is required to ascertain acceptable repeatability in multiple sessions and rotational accuracy.

Control of manipulator collision avoidance by using computer‐aided potential field method is studied. A repulsive force is artificially created using the distances between the robot links and obstacles, which are generated by a distance computation algorithm. Typical approaches for definition of link coordinate frames and kinematics computations are adopted. Control gains in the potential field control model are selected with respect to the ranges of the angular velocity and angular acceleration of an industrial robot. Results on collision detection and collision avoidance control are presented. Using a high‐speed personal computer, real‐time manipulator control was achieved. From the results, changing repulsive force gain can change the safety distance. This makes the safety zone adjustable and provides greater intelligence for robotic tasks under the ever‐changing environment.

In order to improve the real-time and accuracy in the collision detection technology, a collision detection algorithm based on spatial partitioning and bounding volume was proposed . This algorithm adopted different spatial division strategies for different locations of the spaces according to the details in the scenes to exclude objects which can not intersect.Thus defined the potential intersection areas. Then we used a dynamic S-AABB hierarchy bounding boxes to test whether the intersection happened between the objects in the same grids. We used the sphere boxes to rule out the disjoint objects quickly. Then constructed the dynamic AABB bounding boxes trees for the rest of objects for further intersection test. At last, we improved the traditional overlapping test between the primitives for accurate collision detection . Compared to the traditional collision detection algorithm based on spatial partitioning and AABB bounding volume. This algorithm effectively improves the real-time of the collision detection without affecting the accuracy of original collision detection.

Based on the potential of current programmable GPUs, recently several approaches were developed that use the GPU to calculate deformations of surfaces like the folding of cloth or to convert higher level geometry to renderable primitives like NURBS or subdivision surfaces. These algorithms are realized as a per‐frame operation and take advantage of the parallel processing power of the GPU. Unfortunately, an efficient accurate collision detection, that is necessary for the simulation itself or for the interaction with and editing of the objects, can currently not be integrated seamlessly into these GPU‐based approaches without switching back to the CPU. In this paper we describe a novel GPU‐based collision detection method for deformable parameterized surfaces that can easily be combined with the aforementioned approaches. Representing the individual parameterized surfaces by stenciled geometry images allows to generate GPU‐optimized bounding volume hierarchies in real‐time that serve as a basis for an optimized GPU‐based hierarchical collision detection algorithm. As a test case we applied our algorithm to the collision detection of deformable trimmed NURBS models, which is an important problem in industry. For the trimming and tessellation of the NURBS on the GPU we used a recent approach [GBK05] and combined it with our collision detection algorithm. This way we are able to render and check collisions for deformable models consisting of several thousands of trimmed NURBS patches in real‐time. Categories and Subject Descriptors (according to ACM CCS): I.3.5 [Computer Graphics]: Computational Geometry and Object Modeling—Geometric algorithms, languages, and systems; Splines; I.3.7 [Computer Graphics]: Three‐Dimensional Graphics and Realism—Virtual reality

We present new distance computation algorithms using hierarchies of rectangular swept spheres. Each bounding volume of the tree is described as the Minkowski sum of a rectangle and a sphere, and fits tightly to the underlying geometry. We present accurate and efficient algorithms to build the hierarchies and perform distance queries between the bounding volumes. We also present traversal techniques for accelerating distance queries using coherence and priority directed search. These algorithms have been used to perform proximity queries for applications including virtual prototyping, dynamic simulation, and motion planning on complex models. As compared to earlier algorithms based on bounding volume hierarchies for separation distance and approximate distance computation, our algorithms have achieved significant speedups on many benchmarks.

The step size of least mean square (LMS) algorithm is significant for its performance. To be specific, small step size can get small excess mean square error but results in slow convergence. However, large step size may cause instability. Many variable step size least mean square (VSSLMS) algorithms have been developed to enhance the control performance. In this paper, a new VSSLMS was proposed based on Kwong’s algorithm to evaluate the robustness. The approximate analysis of dynamic and steady-state performance of this developed VSSLMS algorithm was given. An active vibration control system of piezoelectric cantilever beam was established to verify the performance of the VSSLMS algorithms. By comparing with the current VSSLMS algorithms, the proposed method has better performance in active vibration control applications.

Antenna array has been extensively applied to wireless communication systems. Optimal design of antenna array is very useful to attain desired spatial beam and reduce signal degradation. Potential search directions in artificial bee colony (ABC) algorithm are mixed with both large step size and small step size. This could lead to the malfunction of employed bee stage and onlooker bee stage of ABC algorithm. This paper proposes to improve the effectiveness of ABC by a similarity induced search method. This method adaptively adjusts search step size. Employed bees perform large step size search, while onlooker bees do small step size search. Scout bees could probe potential high-quality solutions in neighborhoods. The proposed algorithm is tested on antenna array design problem. Compared with four other algorithms, the results verify the effectiveness of the proposed algorithm. Furthermore, the scalability of the proposed algorithm is also analyzed in terms of array element and computational time. Scalability analysis also shows that the proposed algorithm is suitable for solving antenna array design problems.