D. Manocha - Academia.edu (original) (raw)

Papers by D. Manocha

IEEE Transactions on Visualization and Computer Graphics, 2005

We present a novel approach for interactive view-dependent rendering of massive models. Our algor... more We present a novel approach for interactive view-dependent rendering of massive models. Our algorithm combines viewdependent simplification, occlusion culling, and out-of-core rendering. We represent the model as a clustered hierarchy of progressive meshes (CHPM). We use the cluster hierarchy for coarse-grained selective refinement and progressive meshes for fine-grained local refinement. We present an out-of-core algorithm for computation of a CHPM that includes cluster decomposition, hierarchy generation, and simplification. We introduce novel cluster dependencies in the preprocess to generate crack-free, drastic simplifications at runtime. The clusters are used for LOD selection, occlusion culling, and out-of-core rendering. We add a frame of latency to the rendering pipeline to fetch newly visible clusters from the disk and avoid stalls. The CHPM reduces the refinement cost of view-dependent rendering by more than an order of magnitude as compared to a vertex hierarchy. We have implemented our algorithm on a desktop PC. We can render massive CAD, isosurface, and scanned models, consisting of tens or a few hundred million triangles at 15-35 frames per second with little loss in image quality.

Proceedings 2002 IEEE International Conference on Robotics and Automation (Cat. No.02CH37292)

We present an incremental algorithm to estimate the penetration depth between convex polytopes in... more We present an incremental algorithm to estimate the penetration depth between convex polytopes in 3D. The algorithm incrementally seeks a "locally optimal solution" by walking on the surface of the Minkowski sums. The surface of the Minkowski sums is computed implicitly by constructing a local Gauss map. In practice, the algorithm works well when there is high motion coherence in the environment and is able to compute the optimal solution in most cases.

Proceedings of the 2001 symposium on Interactive 3D graphics - SI3D '01, 2001

We present a new approach for computing generalized proximity information of arbitrary 2D objects... more We present a new approach for computing generalized proximity information of arbitrary 2D objects using graphics hardware. Using multi-pass rendering techniques and accelerated distance computation, our algorithm performs proximity queries not only for detecting collisions, but also for computing intersections, separation distance, penetration depth, and contact points and normals. Our hybrid geometry and image-based approach balances computation between the CPU and graphics subsystems. Geometric object-space techniques coarsely localize potential intersection regions or closest features between two objects, and image-space techniques compute the low-level proximity information in these regions. Most of the proximity information is derived from a distance field computed using graphics hardware. We demonstrate the performance in collision response computation for rigid and deformable body dynamics simulations. Our approach provides proximity information at interactive rates for a variety of simulation strategies for both backtracking and penalty-based collision responses.

2013 IEEE International Conference on Robotics and Automation, 2013

We present a novel algorithm to compute collision-free trajectories in dynamic environments. Our ... more We present a novel algorithm to compute collision-free trajectories in dynamic environments. Our approach is general and makes no assumption about the obstacles or their motion. We use a replanning framework that interleaves optimization-based planning with execution. Furthermore, we describe a parallel formulation that exploits high number of cores on commodity graphics processors (GPUs) to compute a high-quality path in a given time interval. We derive bounds on how parallelization can improve the responsiveness of the planner and the quality of the trajectory.

2009 IEEE International Conference on Robotics and Automation, 2009

We present a novel approach to compute collisionfree paths for multiple robots subject to local c... more We present a novel approach to compute collisionfree paths for multiple robots subject to local coordination constraints. More specifically, given a set of robots, their initial and final configurations, and possibly some additional coordination constraints, our goal is to compute a collision-free path between the initial and final configuration that maintains the constraints. To solve this problem, our approach generalizes the social potential field method to be applicable to both convex and nonconvex polyhedra. Social potential fields are then integrated into a "physics-based motion planning" framework which uses constrained dynamics to solve the motion planning problem. Our approach is able to plan for over 200 robots while averaging about 110 ms per step in a variety of environments.

Springer Tracts in Advanced Robotics, 2013

We present a novel approach to improve the performance of sample-based motion planners by learnin... more We present a novel approach to improve the performance of sample-based motion planners by learning from prior instances. Our formulation stores the results of prior collision and local planning queries. This information is used to accelerate the performance of planners based on probabilistic collision checking, select new local paths in free space, and compute an efficient order to perform queries along a search path in a graph. We present fast and novel algorithms to perform k-NN (k-nearest neighbor) queries in high dimensional configuration spaces based on locality-sensitive hashing and derive tight bounds on their accuracy. The k-NN queries are used to perform instance-based learning and have a sub-linear time complexity. Our approach is general, makes no assumption about the sampling scheme, and can be used with various sample-based motion planners, including PRM, Lazy-PRM, RRT and RRT * , by making small changes to these planners. We observe up to 100% improvement in the performance of various planners on rigid and articulated robots. Jia Pan and Dinesh Manocha are with the Department of Computer Science,

Proceedings of the 2002 ACM SIGGRAPH/Eurographics symposium on Computer animation - SCA '02, 2002

We present a novel and fast algorithm to compute penetration depth (PD) between two polyhedral mo... more We present a novel and fast algorithm to compute penetration depth (PD) between two polyhedral models for physically-based animation. Given two overlapping polyhedra, it computes the minimal translation distance to separate them using a combination of objectspace and image-space techniques. The algorithm computes pairwise Minkowski sums of decomposed convex pieces and performs a closest point query using rasterization hardware. It uses bounding volume hierarchies, object-space and image-space culling algorithms to further accelerate the computation and refines the estimated PD in a hierarchical manner. We demonstrate its application to contact response computation and a time-stepping method for dynamic simulation.

We introduce a novel online method to predict pedestrian trajectories using agent-based velocity-... more We introduce a novel online method to predict pedestrian trajectories using agent-based velocity-space reasoning for improved human-robot interaction and collision-free navigation. Our formulation uses velocity obstacles to model the trajectory of each moving pedestrian in a robot's environment and improves the motion model by adaptively learning relevant parameters based on sensor data. The resulting motion model for each agent is computed using statistical inferencing techniques, including a combination of Ensemble Kalman filters and a maximum-likelihood estimation algorithm. This allows a robot to learn individual motion parameters for every agent in the scene at interactive rates. We highlight the performance of our approach for collision-free robot navigation among pedestrians based on noisy, sparsely-sampled data and highlight the results in our simulator.

ACM International Conference Proceeding Series, 2004

We present a novel approach for collision detection between large models composed of tens of mill... more We present a novel approach for collision detection between large models composed of tens of millions of polygons. Each model is represented as a clustered hierarchy of progressive meshes (CHPM). The CHPM is a dual hierarchy of the original model; it serves both as a multiresolution representation of the original model, as well as a bounding volume hierarchy. We use the cluster hierarchy of a CHPM to perform coarse-grained selective refinement and the progressive meshes for fine-grained local refinement. We present a novel conservative error metric to perform collision queries based on the multiresolution representation. We use this error metric to perform dynamic simplification for collision detection. Our approach is conservative in that it may overestimate the set of colliding regions, but never misses any collisions. Furthermore, we are able to generate these hierarchies and perform collision queries using out-of-core techniques on all triangulated models. We have applied our algorithm to perform conservative collision detection between massive CAD and scanned models, consisting of millions of triangles at interactive rates on a commodity PC.

Proceedings - IEEE International Conference on Robotics and Automation, 2006

We present a simple algorithm for approximating the free configuration space of robots with low d... more We present a simple algorithm for approximating the free configuration space of robots with low degrees of freedom (DOFs). We represent the free space as an arrangement of contact surfaces. We approximate the free space using an adaptive volumetric grid that is computed by performing simple geometric tests on the contact surfaces. We use an isosurface extraction algorithm to compute a piecewise-linear approximation to the boundary of the free space. We prove that our approximation is topologically equivalent to the exact free space boundary. We also ensure that our approximation is geometrically close to the exact free space boundary by bounding its two-sided Hausdorff error. We have applied our algorithm to compute the free configuration space for the following instances: (1) a 2D polygonal robot with translational and rotational DOFs navigating among polygonal obstacles, and (2) a 3D polyhedral robot translating among polyhedral obstacles. In practice, our algorithm works well on robots with three DOFs.

IEEE International Conference on Intelligent Robots and Systems, 2007

We present a novel algorithm for motion planning of multiple robots amongst dynamic obstacles. Ou... more We present a novel algorithm for motion planning of multiple robots amongst dynamic obstacles. Our approach is based on a new roadmap representation that uses deformable links and dynamically retracts to capture the connectivity of the free space. We use Newtonian Physics and Hooke's Law to update the position of the milestones and deform the links in response to the motion of other robots and the obstacles. Based on this roadmap representation, we describe our planning algorithms that can compute collision-free paths for tens of robots in complex dynamic environments.

ACM SIGGRAPH 2007 Sketches, SIGGRAPH'07, 2007

We present a novel algorithm to selectively restructure bounding volume hierarchies (BVHs) for ra... more We present a novel algorithm to selectively restructure bounding volume hierarchies (BVHs) for ray tracing dynamic scenes. We derive two new metrics to evaluate the culling efficiency and restructuring benefit of any BVH. Based on these metrics, we perform selective restructuring operations that efficiently reconstruct small portions of a BVH instead of the entire BVH. Our approach is general and applicable to complex and dynamic scenes, including topological changes. We use the selective restructuring algorithm to improve the performance of ray tracing dynamic scenes that consist of hundreds of thousands of triangles. In our benchmarks, we observe up to an order of magnitude improvement over prior BVH-based ray tracing algorithms.

IEEE International Conference on Intelligent Robots and Systems, 2007

We present an efficient algorithm for complete motion planning that combines approximate cell dec... more We present an efficient algorithm for complete motion planning that combines approximate cell decomposition (ACD) with probabilistic roadmaps (PRM). Our approach uses ACD to subdivide the configuration space into cells and computes localized roadmaps by generating samples within these cells. We augment the connectivity graph for adjacent cells in ACD with pseudo-free edges that are computed based on localized roadmaps. These roadmaps are used to capture the connectivity of free space and guide the adaptive subdivision algorithm. At the same time, we use cell decomposition to check for path non-existence and generate samples in narrow passages. Overall, our hybrid algorithm combines the efficiency of PRM methods with the completeness of ACD-based algorithms. We have implemented our algorithm on 3-DOF and 4-DOF robots. We demonstrate its performance on planning scenarios with narrow passages or no collision-free paths. In practice, we observe up to 10 times improvement in performance over prior complete motion planning algorithms.

ACM SIGGRAPH 2008 Classes, 2008

We present a novel approach for real-time path planning of multiple virtual agents in complex dyn... more We present a novel approach for real-time path planning of multiple virtual agents in complex dynamic scenes. We introduce a new data structure, Multi-agent Navigation Graph (MaNG), which is constructed from the first-and second-order Voronoi diagrams. The MaNG is used to perform route planning and proximity computations for each agent in real time. We compute the MaNG using graphics hardware and present culling techniques to accelerate the computation. We also address undersampling issues for accurate computation. Our algorithm is used for real-time multi-agent planning in pursuit-evasion and crowd simulation scenarios consisting of hundreds of moving agents, each with a distinct goal.

ACM SIGGRAPH 2008 Classes, 2008

We present a novel algorithm for navigating a large number of independent agents in complex and d... more We present a novel algorithm for navigating a large number of independent agents in complex and dynamic environments. We compute adaptive roadmaps to perform global path planning for each agent simultaneously. We take into account dynamic obstacles and inter-agents interaction forces to continuously update the roadmap by using a physically-based agent dynamics simulator. We also introduce the notion of 'link bands' for resolving collisions among multiple agents. We present efficient techniques to compute the guiding path forces and perform lazy updates to the roadmap. In practice, our algorithm can perform real-time navigation of hundreds and thousands of human agents in indoor and outdoor scenes.

9th IEEE-RAS International Conference on Humanoid Robots, HUMANOIDS09, 2009

We present a whole-body motion planning algorithm for human-like robots. The planning problem is ... more We present a whole-body motion planning algorithm for human-like robots. The planning problem is decomposed into a sequence of low-dimensional sub-problems. Our formulation is based on the fact that a human-like model is a tightly coupled system and uses a constrained coordination scheme to solve the sub-problems in an incremental manner. We also present a local path refinement algorithm to compute collision-free paths in tight spaces and satisfy the statically stable constraint on CoM. We demonstrate the performance of our algorithm on an articulated human-like model and generate efficient motion strategies for walking, sitting and grabbing objects in complex CAD models.

Proceedings - I3D 2012: ACM SIGGRAPH Symposium on Interactive 3D Graphics and Games, 2012

It is a common artifact of multi-agent motion planning for groups of agents, following similar pa... more It is a common artifact of multi-agent motion planning for groups of agents, following similar paths, to converge to a line. This occurs because the agents' immediate goals, a.k.a. way points, are frequently a shared point in space. Contention for the point goal causes agents to line up and generally interferes with agent motion. By extending the definition of an immediate point goal to a line segment, which we call a "way portal", we enable the agents to better utilize the space available to them in responding to dynamic constraints. We present a novel multi-agent navigation algorithm to efficiently compute the trajectories of autonomous agents using these way portals. We have incorporated the concept into a velocity obstacle-based local navigation model and present a new segment optimization algorithm that efficiently computes a new agent velocity with respect to the way portal. We show how way portal data is extracted from current global navigation data structures, such as navigation meshes. The algorithm is relatively simple to implement and has a small run-time cost (approximately 3 µs per agent.) We highlight its performance in different game-like scenarios and observe improved agent behavior and better utilization of free space.

Proceedings - IEEE International Conference on Robotics and Automation, 2012

We present a new collision and proximity library that integrates several techniques for fast and ... more We present a new collision and proximity library that integrates several techniques for fast and accurate collision checking and proximity computation. Our library is based on hierarchical representations and designed to perform multiple proximity queries on different model representations. The set of queries includes discrete collision detection, continuous collision detection, separation distance computation and penetration depth estimation. The input models may correspond to triangulated rigid or deformable models and articulated models. Moreover, FCL can perform probabilistic collision checking between noisy point clouds that are captured using cameras or LIDAR sensors. The main benefit of FCL lies in the fact that it provides a unified interface that can be used by various applications. Furthermore, its flexible architecture makes it easier to implement new algorithms within this framework. The runtime performance of the library is comparable to state of the art collision and proximity algorithms. We demonstrate its performance on synthetic datasets as well as motion planning and grasping computations performed using a two-armed mobile manipulation robot.

Proceedings - IEEE Virtual Reality, 2012

We present a new algorithm to simulate a variety of crowd behaviors using the Discrete Choice Mod... more We present a new algorithm to simulate a variety of crowd behaviors using the Discrete Choice Model (DCM). DCM has been widely studied in econometrics to examine and predict customers' or households' choices. Our DCM formulation can simulate virtual agents' goal selection and we highlight our algorithm by simulating heterogeneous crowd behaviors: evacuation, shopping, and rioting scenarios.

2009 IEEE/RSJ International Conference on Intelligent Robots and Systems, 2009

We address the problem of real-time navigation in dynamic environments for car-like robots. We pr... more We address the problem of real-time navigation in dynamic environments for car-like robots. We present an approach to identify controls that will lead to a collision with a moving obstacle at some point in the future. Our approach generalizes the concept of velocity obstacles, which have been used for navigation among dynamic obstacles, and takes into account the constraints of a car-like robot. We use this formulation to find controls that will allow collision free navigation in dynamic environments. Finally, we demonstrate the performance of our algorithm on a simulated car-like robot among moving obstacles.

IEEE Transactions on Visualization and Computer Graphics, 2005

We present a novel approach for interactive view-dependent rendering of massive models. Our algor... more We present a novel approach for interactive view-dependent rendering of massive models. Our algorithm combines viewdependent simplification, occlusion culling, and out-of-core rendering. We represent the model as a clustered hierarchy of progressive meshes (CHPM). We use the cluster hierarchy for coarse-grained selective refinement and progressive meshes for fine-grained local refinement. We present an out-of-core algorithm for computation of a CHPM that includes cluster decomposition, hierarchy generation, and simplification. We introduce novel cluster dependencies in the preprocess to generate crack-free, drastic simplifications at runtime. The clusters are used for LOD selection, occlusion culling, and out-of-core rendering. We add a frame of latency to the rendering pipeline to fetch newly visible clusters from the disk and avoid stalls. The CHPM reduces the refinement cost of view-dependent rendering by more than an order of magnitude as compared to a vertex hierarchy. We have implemented our algorithm on a desktop PC. We can render massive CAD, isosurface, and scanned models, consisting of tens or a few hundred million triangles at 15-35 frames per second with little loss in image quality.

Proceedings 2002 IEEE International Conference on Robotics and Automation (Cat. No.02CH37292)

We present an incremental algorithm to estimate the penetration depth between convex polytopes in... more We present an incremental algorithm to estimate the penetration depth between convex polytopes in 3D. The algorithm incrementally seeks a "locally optimal solution" by walking on the surface of the Minkowski sums. The surface of the Minkowski sums is computed implicitly by constructing a local Gauss map. In practice, the algorithm works well when there is high motion coherence in the environment and is able to compute the optimal solution in most cases.

Proceedings of the 2001 symposium on Interactive 3D graphics - SI3D '01, 2001

We present a new approach for computing generalized proximity information of arbitrary 2D objects... more We present a new approach for computing generalized proximity information of arbitrary 2D objects using graphics hardware. Using multi-pass rendering techniques and accelerated distance computation, our algorithm performs proximity queries not only for detecting collisions, but also for computing intersections, separation distance, penetration depth, and contact points and normals. Our hybrid geometry and image-based approach balances computation between the CPU and graphics subsystems. Geometric object-space techniques coarsely localize potential intersection regions or closest features between two objects, and image-space techniques compute the low-level proximity information in these regions. Most of the proximity information is derived from a distance field computed using graphics hardware. We demonstrate the performance in collision response computation for rigid and deformable body dynamics simulations. Our approach provides proximity information at interactive rates for a variety of simulation strategies for both backtracking and penalty-based collision responses.

2013 IEEE International Conference on Robotics and Automation, 2013

We present a novel algorithm to compute collision-free trajectories in dynamic environments. Our ... more We present a novel algorithm to compute collision-free trajectories in dynamic environments. Our approach is general and makes no assumption about the obstacles or their motion. We use a replanning framework that interleaves optimization-based planning with execution. Furthermore, we describe a parallel formulation that exploits high number of cores on commodity graphics processors (GPUs) to compute a high-quality path in a given time interval. We derive bounds on how parallelization can improve the responsiveness of the planner and the quality of the trajectory.

2009 IEEE International Conference on Robotics and Automation, 2009

We present a novel approach to compute collisionfree paths for multiple robots subject to local c... more We present a novel approach to compute collisionfree paths for multiple robots subject to local coordination constraints. More specifically, given a set of robots, their initial and final configurations, and possibly some additional coordination constraints, our goal is to compute a collision-free path between the initial and final configuration that maintains the constraints. To solve this problem, our approach generalizes the social potential field method to be applicable to both convex and nonconvex polyhedra. Social potential fields are then integrated into a "physics-based motion planning" framework which uses constrained dynamics to solve the motion planning problem. Our approach is able to plan for over 200 robots while averaging about 110 ms per step in a variety of environments.

Springer Tracts in Advanced Robotics, 2013

We present a novel approach to improve the performance of sample-based motion planners by learnin... more We present a novel approach to improve the performance of sample-based motion planners by learning from prior instances. Our formulation stores the results of prior collision and local planning queries. This information is used to accelerate the performance of planners based on probabilistic collision checking, select new local paths in free space, and compute an efficient order to perform queries along a search path in a graph. We present fast and novel algorithms to perform k-NN (k-nearest neighbor) queries in high dimensional configuration spaces based on locality-sensitive hashing and derive tight bounds on their accuracy. The k-NN queries are used to perform instance-based learning and have a sub-linear time complexity. Our approach is general, makes no assumption about the sampling scheme, and can be used with various sample-based motion planners, including PRM, Lazy-PRM, RRT and RRT * , by making small changes to these planners. We observe up to 100% improvement in the performance of various planners on rigid and articulated robots. Jia Pan and Dinesh Manocha are with the Department of Computer Science,

Proceedings of the 2002 ACM SIGGRAPH/Eurographics symposium on Computer animation - SCA '02, 2002

We present a novel and fast algorithm to compute penetration depth (PD) between two polyhedral mo... more We present a novel and fast algorithm to compute penetration depth (PD) between two polyhedral models for physically-based animation. Given two overlapping polyhedra, it computes the minimal translation distance to separate them using a combination of objectspace and image-space techniques. The algorithm computes pairwise Minkowski sums of decomposed convex pieces and performs a closest point query using rasterization hardware. It uses bounding volume hierarchies, object-space and image-space culling algorithms to further accelerate the computation and refines the estimated PD in a hierarchical manner. We demonstrate its application to contact response computation and a time-stepping method for dynamic simulation.

We introduce a novel online method to predict pedestrian trajectories using agent-based velocity-... more We introduce a novel online method to predict pedestrian trajectories using agent-based velocity-space reasoning for improved human-robot interaction and collision-free navigation. Our formulation uses velocity obstacles to model the trajectory of each moving pedestrian in a robot's environment and improves the motion model by adaptively learning relevant parameters based on sensor data. The resulting motion model for each agent is computed using statistical inferencing techniques, including a combination of Ensemble Kalman filters and a maximum-likelihood estimation algorithm. This allows a robot to learn individual motion parameters for every agent in the scene at interactive rates. We highlight the performance of our approach for collision-free robot navigation among pedestrians based on noisy, sparsely-sampled data and highlight the results in our simulator.

ACM International Conference Proceeding Series, 2004

We present a novel approach for collision detection between large models composed of tens of mill... more We present a novel approach for collision detection between large models composed of tens of millions of polygons. Each model is represented as a clustered hierarchy of progressive meshes (CHPM). The CHPM is a dual hierarchy of the original model; it serves both as a multiresolution representation of the original model, as well as a bounding volume hierarchy. We use the cluster hierarchy of a CHPM to perform coarse-grained selective refinement and the progressive meshes for fine-grained local refinement. We present a novel conservative error metric to perform collision queries based on the multiresolution representation. We use this error metric to perform dynamic simplification for collision detection. Our approach is conservative in that it may overestimate the set of colliding regions, but never misses any collisions. Furthermore, we are able to generate these hierarchies and perform collision queries using out-of-core techniques on all triangulated models. We have applied our algorithm to perform conservative collision detection between massive CAD and scanned models, consisting of millions of triangles at interactive rates on a commodity PC.

Proceedings - IEEE International Conference on Robotics and Automation, 2006

We present a simple algorithm for approximating the free configuration space of robots with low d... more We present a simple algorithm for approximating the free configuration space of robots with low degrees of freedom (DOFs). We represent the free space as an arrangement of contact surfaces. We approximate the free space using an adaptive volumetric grid that is computed by performing simple geometric tests on the contact surfaces. We use an isosurface extraction algorithm to compute a piecewise-linear approximation to the boundary of the free space. We prove that our approximation is topologically equivalent to the exact free space boundary. We also ensure that our approximation is geometrically close to the exact free space boundary by bounding its two-sided Hausdorff error. We have applied our algorithm to compute the free configuration space for the following instances: (1) a 2D polygonal robot with translational and rotational DOFs navigating among polygonal obstacles, and (2) a 3D polyhedral robot translating among polyhedral obstacles. In practice, our algorithm works well on robots with three DOFs.

IEEE International Conference on Intelligent Robots and Systems, 2007

We present a novel algorithm for motion planning of multiple robots amongst dynamic obstacles. Ou... more We present a novel algorithm for motion planning of multiple robots amongst dynamic obstacles. Our approach is based on a new roadmap representation that uses deformable links and dynamically retracts to capture the connectivity of the free space. We use Newtonian Physics and Hooke's Law to update the position of the milestones and deform the links in response to the motion of other robots and the obstacles. Based on this roadmap representation, we describe our planning algorithms that can compute collision-free paths for tens of robots in complex dynamic environments.

ACM SIGGRAPH 2007 Sketches, SIGGRAPH'07, 2007

We present a novel algorithm to selectively restructure bounding volume hierarchies (BVHs) for ra... more We present a novel algorithm to selectively restructure bounding volume hierarchies (BVHs) for ray tracing dynamic scenes. We derive two new metrics to evaluate the culling efficiency and restructuring benefit of any BVH. Based on these metrics, we perform selective restructuring operations that efficiently reconstruct small portions of a BVH instead of the entire BVH. Our approach is general and applicable to complex and dynamic scenes, including topological changes. We use the selective restructuring algorithm to improve the performance of ray tracing dynamic scenes that consist of hundreds of thousands of triangles. In our benchmarks, we observe up to an order of magnitude improvement over prior BVH-based ray tracing algorithms.

IEEE International Conference on Intelligent Robots and Systems, 2007

We present an efficient algorithm for complete motion planning that combines approximate cell dec... more We present an efficient algorithm for complete motion planning that combines approximate cell decomposition (ACD) with probabilistic roadmaps (PRM). Our approach uses ACD to subdivide the configuration space into cells and computes localized roadmaps by generating samples within these cells. We augment the connectivity graph for adjacent cells in ACD with pseudo-free edges that are computed based on localized roadmaps. These roadmaps are used to capture the connectivity of free space and guide the adaptive subdivision algorithm. At the same time, we use cell decomposition to check for path non-existence and generate samples in narrow passages. Overall, our hybrid algorithm combines the efficiency of PRM methods with the completeness of ACD-based algorithms. We have implemented our algorithm on 3-DOF and 4-DOF robots. We demonstrate its performance on planning scenarios with narrow passages or no collision-free paths. In practice, we observe up to 10 times improvement in performance over prior complete motion planning algorithms.

ACM SIGGRAPH 2008 Classes, 2008

We present a novel approach for real-time path planning of multiple virtual agents in complex dyn... more We present a novel approach for real-time path planning of multiple virtual agents in complex dynamic scenes. We introduce a new data structure, Multi-agent Navigation Graph (MaNG), which is constructed from the first-and second-order Voronoi diagrams. The MaNG is used to perform route planning and proximity computations for each agent in real time. We compute the MaNG using graphics hardware and present culling techniques to accelerate the computation. We also address undersampling issues for accurate computation. Our algorithm is used for real-time multi-agent planning in pursuit-evasion and crowd simulation scenarios consisting of hundreds of moving agents, each with a distinct goal.

ACM SIGGRAPH 2008 Classes, 2008

We present a novel algorithm for navigating a large number of independent agents in complex and d... more We present a novel algorithm for navigating a large number of independent agents in complex and dynamic environments. We compute adaptive roadmaps to perform global path planning for each agent simultaneously. We take into account dynamic obstacles and inter-agents interaction forces to continuously update the roadmap by using a physically-based agent dynamics simulator. We also introduce the notion of 'link bands' for resolving collisions among multiple agents. We present efficient techniques to compute the guiding path forces and perform lazy updates to the roadmap. In practice, our algorithm can perform real-time navigation of hundreds and thousands of human agents in indoor and outdoor scenes.

9th IEEE-RAS International Conference on Humanoid Robots, HUMANOIDS09, 2009

We present a whole-body motion planning algorithm for human-like robots. The planning problem is ... more We present a whole-body motion planning algorithm for human-like robots. The planning problem is decomposed into a sequence of low-dimensional sub-problems. Our formulation is based on the fact that a human-like model is a tightly coupled system and uses a constrained coordination scheme to solve the sub-problems in an incremental manner. We also present a local path refinement algorithm to compute collision-free paths in tight spaces and satisfy the statically stable constraint on CoM. We demonstrate the performance of our algorithm on an articulated human-like model and generate efficient motion strategies for walking, sitting and grabbing objects in complex CAD models.

Proceedings - I3D 2012: ACM SIGGRAPH Symposium on Interactive 3D Graphics and Games, 2012

It is a common artifact of multi-agent motion planning for groups of agents, following similar pa... more It is a common artifact of multi-agent motion planning for groups of agents, following similar paths, to converge to a line. This occurs because the agents' immediate goals, a.k.a. way points, are frequently a shared point in space. Contention for the point goal causes agents to line up and generally interferes with agent motion. By extending the definition of an immediate point goal to a line segment, which we call a "way portal", we enable the agents to better utilize the space available to them in responding to dynamic constraints. We present a novel multi-agent navigation algorithm to efficiently compute the trajectories of autonomous agents using these way portals. We have incorporated the concept into a velocity obstacle-based local navigation model and present a new segment optimization algorithm that efficiently computes a new agent velocity with respect to the way portal. We show how way portal data is extracted from current global navigation data structures, such as navigation meshes. The algorithm is relatively simple to implement and has a small run-time cost (approximately 3 µs per agent.) We highlight its performance in different game-like scenarios and observe improved agent behavior and better utilization of free space.

Proceedings - IEEE International Conference on Robotics and Automation, 2012

We present a new collision and proximity library that integrates several techniques for fast and ... more We present a new collision and proximity library that integrates several techniques for fast and accurate collision checking and proximity computation. Our library is based on hierarchical representations and designed to perform multiple proximity queries on different model representations. The set of queries includes discrete collision detection, continuous collision detection, separation distance computation and penetration depth estimation. The input models may correspond to triangulated rigid or deformable models and articulated models. Moreover, FCL can perform probabilistic collision checking between noisy point clouds that are captured using cameras or LIDAR sensors. The main benefit of FCL lies in the fact that it provides a unified interface that can be used by various applications. Furthermore, its flexible architecture makes it easier to implement new algorithms within this framework. The runtime performance of the library is comparable to state of the art collision and proximity algorithms. We demonstrate its performance on synthetic datasets as well as motion planning and grasping computations performed using a two-armed mobile manipulation robot.

Proceedings - IEEE Virtual Reality, 2012

We present a new algorithm to simulate a variety of crowd behaviors using the Discrete Choice Mod... more We present a new algorithm to simulate a variety of crowd behaviors using the Discrete Choice Model (DCM). DCM has been widely studied in econometrics to examine and predict customers' or households' choices. Our DCM formulation can simulate virtual agents' goal selection and we highlight our algorithm by simulating heterogeneous crowd behaviors: evacuation, shopping, and rioting scenarios.

2009 IEEE/RSJ International Conference on Intelligent Robots and Systems, 2009

We address the problem of real-time navigation in dynamic environments for car-like robots. We pr... more We address the problem of real-time navigation in dynamic environments for car-like robots. We present an approach to identify controls that will lead to a collision with a moving obstacle at some point in the future. Our approach generalizes the concept of velocity obstacles, which have been used for navigation among dynamic obstacles, and takes into account the constraints of a car-like robot. We use this formulation to find controls that will allow collision free navigation in dynamic environments. Finally, we demonstrate the performance of our algorithm on a simulated car-like robot among moving obstacles.