The Local Clearance Triangulation (LCT) of polygonal obstacles is a cell decomposition designed f... more The Local Clearance Triangulation (LCT) of polygonal obstacles is a cell decomposition designed for the efficient computation of locally shortest paths with clearance. This article presents a revised definition of LCTs, new theoretical results and optimizations, and new algorithms introducing dynamic updates and robustness. Given an input obstacle set with n vertices, a theoretical analysis is proposed showing that LCTs generate a triangular decomposition of O ( n ) cells, guaranteeing that discrete search algorithms can compute paths in optimal times. In addition, several examples are presented indicating that the number of triangles is low in practice, close to 2 n , and a new technique is described for reducing the number of triangles when the maximum query clearance is known in advance. Algorithms for repairing the local clearance property dynamically are also introduced, leading to efficient LCT updates for addressing dynamic changes in the obstacle set. Dynamic updates automat...
IEEE International Conference on Robotics and Automation, 2004. Proceedings. ICRA '04. 2004, 2004
We evaluate the use of dynamic roadmaps for online motion planning in changing environments. When... more We evaluate the use of dynamic roadmaps for online motion planning in changing environments. When changes are detected in the workspace, the validity state of affected edges and nodes of a precomputed roadmap are updated accordingly. We concentrate in this paper on analyzing the tradeoffs between maintaining dynamic roadmaps and applying an on-line bidirectional Rapidly-exploring Random Tree (RRT) planner alone, which requires no preprocessing or maintenance. We ground the analysis in several benchmarks in virtual environments with randomly moving obstacles. Different robotics structures are used, including a 17 degrees of freedom model of NASA's Robonaut humanoid. Our results show that dynamic roadmaps can be both faster and more capable for planning difficult motions than using on-line planning alone. In particular, we investigate its scalability to 3D workspaces and higher dimensional configurations spaces, as our main interest is the application of the method to interactive domains involving humanoids.
4th IEEE/RAS International Conference on Humanoid Robots, 2004.
The problem of humanoid agents and robots reaching to arbitrary targets in environments with stat... more The problem of humanoid agents and robots reaching to arbitrary targets in environments with static and dynamic obstacles has not yet been investigated in detail. Typical approaches include using randomized motion planning or constructing uninformed trajectories (e.g., linear interpolation between initial and target positions and orientations of the hand) in operational space, in hopes that inter-link and agent-environment collisions do not occur. In this paper, we test the most popular algorithms for motion generation for single-arm reaching in environments with randomly placed obstacles of random sizes. Additionally, we attempt to formalize the concept of motor primitives, and test a motor primitive implementation in the same experiments. We conduct an analysis of the efficacy of the algorithms for reaching in static environments, and discuss the extensibility of the algorithms towards reaching in dynamic environments.
2010 IEEE International Conference on Robotics and Automation, 2010
This paper presents a multi-skill motion planner which is able to sequentially synchronize parame... more This paper presents a multi-skill motion planner which is able to sequentially synchronize parameterized motion skills in order to achieve humanoid motions exhibiting complex whole-body coordination. The proposed approach integrates sampling-based motion planning in continuous parametric spaces with discrete search over skill choices, selecting the search strategy according to the functional type of each skill being coordinated. As a result, the planner is able to sequence arbitrary motion skills (such as reaching, balance adjustment, stepping, etc) in order to achieve complex motions needed for solving humanoid reaching tasks in realistic environments. The proposed framework is applied to the HOAP-3 humanoid robot and several results are presented.
2011 IEEE/RSJ International Conference on Intelligent Robots and Systems, 2011
We introduce an approach for enabling samplingbased planners to compute motions with humanlike ap... more We introduce an approach for enabling samplingbased planners to compute motions with humanlike appearance. The proposed method is based on a space of blendable example motions collected by motion capture. This space is explored by a sampling-based planner that is able to produce motions around obstacles while keeping solutions similar to the original examples. The results therefore largely maintain the humanlike characteristics observed in the example motions. The method is applied to generic upper-body actions and is complemented by a locomotion planner that searches for suitable body placements for executing upper-body actions successfully. As a result, our overall multi-modal planning method is able to automatically coordinate whole-body motions for action execution among obstacles, and the produced motions remain similar to example motions given as input to the system.
IEEE Transactions on Visualization and Computer Graphics, 2013
We propose feature-based motion graphs for realistic locomotion synthesis among obstacles. Among ... more We propose feature-based motion graphs for realistic locomotion synthesis among obstacles. Among several advantages, feature-based motion graphs achieve improved results in search queries, eliminate the need of post-processing for foot skating removal, and reduce the computational requirements in comparison to traditional motion graphs. Our contributions are threefold. First, we show that choosing transitions based on relevant features significantly reduces graph construction time and leads to improved search performances. Second, we employ a fast channel search method that confines the motion graph search to a free channel with guaranteed clearance among obstacles, achieving faster and improved results that avoid expensive collision checking. Lastly, we present a motion deformation model based on Inverse Kinematics applied over the transitions of a solution branch. Each transition is assigned a continuous deformation range that does not exceed the original transition cost threshold specified by the user for the graph construction. The obtained deformation improves the reachability of the feature-based motion graph and in turn also reduces the time spent during search. The results obtained by the proposed methods are evaluated and quantified, and they demonstrate significant improvements in comparison to traditional motion graph techniques.
In order to deliver information effectively, virtual human demonstrators must be able to address ... more In order to deliver information effectively, virtual human demonstrators must be able to address complex spatial constraints and at the same time replicate motion coordination patterns observed in human-human interactions. We introduce in this paper a whole-body motion planning and synthesis framework that coordinates locomotion, body positioning, action execution and gaze behavior for generic demonstration tasks among obstacles.
Neuroscience evidence supports the idea that biological adaptive behavior may utilize combination... more Neuroscience evidence supports the idea that biological adaptive behavior may utilize combination and sequences of movement primitives, allowing the motor system to reduce the dimensionality of movement control. We present a framework, using sampling-based motion planning, that is able to automatically determine the sequencing of para metric movement primitives needed to execute a given motion task. Our approach builds a search tree in which nodes are configurations reachable with one or more movement primitives, and edges represent valid paths connecting parent and child nodes. The paths are determined by a motion planner that operates in the parameter space of a single movement primitive. The search tree is expanded with A*-like best-first search using greedy problem-specific heuristics. The benefits of our approach are twofold: 1) planning complex motions becomes more efficient in the reduced dimensionality of each movement primitive, and 2) the ability to plan entire motions con...
We present algorithms for the efficient insertion and removal of constraints in Delaunay Triangul... more We present algorithms for the efficient insertion and removal of constraints in Delaunay Triangulations. Constraints are considered to be points or any kind of polygonal lines. Degenerations such as edge overlapping, self-intersections or duplicated points are allowed and are automatically detected and fixed on line. As a result, a fully Dynamic Constrained Delaunay Triangulation is achieved, able to efficiently maintain a consistent triangulated representation of dynamic polygonal domains. Several applications in the fields of data visualization, reconstruction, geographic information systems and collision-free path planning are discussed.
We present in this paper a new GPU-based approach to compute Shortest Path Maps (SPMs) from a sou... more We present in this paper a new GPU-based approach to compute Shortest Path Maps (SPMs) from a source point in a polygonal domain. Our method takes advantage of GPU polygon rasterization with shader programming. After encoding the SPM in the frame buffer, globally shortest paths are efficiently computed in time proportional to the number of vertices in the path, and length queries are computed in constant time. We have evaluated our method in multiple environments and our results show a significant speedup in comparison to previous approaches.
... It's important to make the difference between the behaviour of a virtual creature and th... more ... It's important to make the difference between the behaviour of a virtual creature and the potential functionality of an object composing the virtual world. For example, the potential functionality of a signpost is to inform, and of a door is to open itself in a specific way. ...
This paper presents a new architecture for simulating virtual humans in complex urban environment... more This paper presents a new architecture for simulating virtual humans in complex urban environments. Our approach is based on the integration of six modules. Four key modules are used in order to: manage environmental data, simulate human crowds, control interactions between virtual humans and objects, and generate tasks based on a rule-based behavioural model. The communication between these modules are made through a Client/Server system. Finally, all lowlevel virtual human actions are delegated to a single motion and behavioural control module. Our architecture combines various human and object simulation aspects, based on the coherent extraction and classification of information from a virtual city database. This architecture is discussed in this paper, together with a detailled case-study example. RBBS CITY Router CROWD SMART OBJECT Controller Message-based communication function calls AGENTlib ACTION PERCEPTION Figure 1 -Representation of the system architecture
This paper investigates the use of 3D immersive virtual environments and 3D prints for interactio... more This paper investigates the use of 3D immersive virtual environments and 3D prints for interaction with past material culture over traditional observation without manipulation. Our work is motivated by studies in heritage, museum, and cognitive sciences indicating the importance of object manipulation for understanding present and ancient artifacts. While virtual immersive environments and 3D prints have started to be incorporated in heritage research and museum displays as a way to provide improved manipulation experiences, little is known about how these new technologies affect the perception of our past. This paper provides first results obtained with three experiments designed to investigate the benefits and tradeoffs in using these technologies. Our results indicate that traditional museum displays limit the experience with past material culture, and reveal how our sample of participants favor tactile and immersive 3D virtual experiences with artifacts over visual non-manipulative experiences with authentic objects.
The Local Clearance Triangulation (LCT) of polygonal obstacles is a cell decomposition designed f... more The Local Clearance Triangulation (LCT) of polygonal obstacles is a cell decomposition designed for the efficient computation of locally shortest paths with clearance. This article presents a revised definition of LCTs, new theoretical results and optimizations, and new algorithms introducing dynamic updates and robustness. Given an input obstacle set with n vertices, a theoretical analysis is proposed showing that LCTs generate a triangular decomposition of O ( n ) cells, guaranteeing that discrete search algorithms can compute paths in optimal times. In addition, several examples are presented indicating that the number of triangles is low in practice, close to 2 n , and a new technique is described for reducing the number of triangles when the maximum query clearance is known in advance. Algorithms for repairing the local clearance property dynamically are also introduced, leading to efficient LCT updates for addressing dynamic changes in the obstacle set. Dynamic updates automat...
IEEE International Conference on Robotics and Automation, 2004. Proceedings. ICRA '04. 2004, 2004
We evaluate the use of dynamic roadmaps for online motion planning in changing environments. When... more We evaluate the use of dynamic roadmaps for online motion planning in changing environments. When changes are detected in the workspace, the validity state of affected edges and nodes of a precomputed roadmap are updated accordingly. We concentrate in this paper on analyzing the tradeoffs between maintaining dynamic roadmaps and applying an on-line bidirectional Rapidly-exploring Random Tree (RRT) planner alone, which requires no preprocessing or maintenance. We ground the analysis in several benchmarks in virtual environments with randomly moving obstacles. Different robotics structures are used, including a 17 degrees of freedom model of NASA's Robonaut humanoid. Our results show that dynamic roadmaps can be both faster and more capable for planning difficult motions than using on-line planning alone. In particular, we investigate its scalability to 3D workspaces and higher dimensional configurations spaces, as our main interest is the application of the method to interactive domains involving humanoids.
4th IEEE/RAS International Conference on Humanoid Robots, 2004.
The problem of humanoid agents and robots reaching to arbitrary targets in environments with stat... more The problem of humanoid agents and robots reaching to arbitrary targets in environments with static and dynamic obstacles has not yet been investigated in detail. Typical approaches include using randomized motion planning or constructing uninformed trajectories (e.g., linear interpolation between initial and target positions and orientations of the hand) in operational space, in hopes that inter-link and agent-environment collisions do not occur. In this paper, we test the most popular algorithms for motion generation for single-arm reaching in environments with randomly placed obstacles of random sizes. Additionally, we attempt to formalize the concept of motor primitives, and test a motor primitive implementation in the same experiments. We conduct an analysis of the efficacy of the algorithms for reaching in static environments, and discuss the extensibility of the algorithms towards reaching in dynamic environments.
2010 IEEE International Conference on Robotics and Automation, 2010
This paper presents a multi-skill motion planner which is able to sequentially synchronize parame... more This paper presents a multi-skill motion planner which is able to sequentially synchronize parameterized motion skills in order to achieve humanoid motions exhibiting complex whole-body coordination. The proposed approach integrates sampling-based motion planning in continuous parametric spaces with discrete search over skill choices, selecting the search strategy according to the functional type of each skill being coordinated. As a result, the planner is able to sequence arbitrary motion skills (such as reaching, balance adjustment, stepping, etc) in order to achieve complex motions needed for solving humanoid reaching tasks in realistic environments. The proposed framework is applied to the HOAP-3 humanoid robot and several results are presented.
2011 IEEE/RSJ International Conference on Intelligent Robots and Systems, 2011
We introduce an approach for enabling samplingbased planners to compute motions with humanlike ap... more We introduce an approach for enabling samplingbased planners to compute motions with humanlike appearance. The proposed method is based on a space of blendable example motions collected by motion capture. This space is explored by a sampling-based planner that is able to produce motions around obstacles while keeping solutions similar to the original examples. The results therefore largely maintain the humanlike characteristics observed in the example motions. The method is applied to generic upper-body actions and is complemented by a locomotion planner that searches for suitable body placements for executing upper-body actions successfully. As a result, our overall multi-modal planning method is able to automatically coordinate whole-body motions for action execution among obstacles, and the produced motions remain similar to example motions given as input to the system.
IEEE Transactions on Visualization and Computer Graphics, 2013
We propose feature-based motion graphs for realistic locomotion synthesis among obstacles. Among ... more We propose feature-based motion graphs for realistic locomotion synthesis among obstacles. Among several advantages, feature-based motion graphs achieve improved results in search queries, eliminate the need of post-processing for foot skating removal, and reduce the computational requirements in comparison to traditional motion graphs. Our contributions are threefold. First, we show that choosing transitions based on relevant features significantly reduces graph construction time and leads to improved search performances. Second, we employ a fast channel search method that confines the motion graph search to a free channel with guaranteed clearance among obstacles, achieving faster and improved results that avoid expensive collision checking. Lastly, we present a motion deformation model based on Inverse Kinematics applied over the transitions of a solution branch. Each transition is assigned a continuous deformation range that does not exceed the original transition cost threshold specified by the user for the graph construction. The obtained deformation improves the reachability of the feature-based motion graph and in turn also reduces the time spent during search. The results obtained by the proposed methods are evaluated and quantified, and they demonstrate significant improvements in comparison to traditional motion graph techniques.
In order to deliver information effectively, virtual human demonstrators must be able to address ... more In order to deliver information effectively, virtual human demonstrators must be able to address complex spatial constraints and at the same time replicate motion coordination patterns observed in human-human interactions. We introduce in this paper a whole-body motion planning and synthesis framework that coordinates locomotion, body positioning, action execution and gaze behavior for generic demonstration tasks among obstacles.
Neuroscience evidence supports the idea that biological adaptive behavior may utilize combination... more Neuroscience evidence supports the idea that biological adaptive behavior may utilize combination and sequences of movement primitives, allowing the motor system to reduce the dimensionality of movement control. We present a framework, using sampling-based motion planning, that is able to automatically determine the sequencing of para metric movement primitives needed to execute a given motion task. Our approach builds a search tree in which nodes are configurations reachable with one or more movement primitives, and edges represent valid paths connecting parent and child nodes. The paths are determined by a motion planner that operates in the parameter space of a single movement primitive. The search tree is expanded with A*-like best-first search using greedy problem-specific heuristics. The benefits of our approach are twofold: 1) planning complex motions becomes more efficient in the reduced dimensionality of each movement primitive, and 2) the ability to plan entire motions con...
We present algorithms for the efficient insertion and removal of constraints in Delaunay Triangul... more We present algorithms for the efficient insertion and removal of constraints in Delaunay Triangulations. Constraints are considered to be points or any kind of polygonal lines. Degenerations such as edge overlapping, self-intersections or duplicated points are allowed and are automatically detected and fixed on line. As a result, a fully Dynamic Constrained Delaunay Triangulation is achieved, able to efficiently maintain a consistent triangulated representation of dynamic polygonal domains. Several applications in the fields of data visualization, reconstruction, geographic information systems and collision-free path planning are discussed.
We present in this paper a new GPU-based approach to compute Shortest Path Maps (SPMs) from a sou... more We present in this paper a new GPU-based approach to compute Shortest Path Maps (SPMs) from a source point in a polygonal domain. Our method takes advantage of GPU polygon rasterization with shader programming. After encoding the SPM in the frame buffer, globally shortest paths are efficiently computed in time proportional to the number of vertices in the path, and length queries are computed in constant time. We have evaluated our method in multiple environments and our results show a significant speedup in comparison to previous approaches.
... It's important to make the difference between the behaviour of a virtual creature and th... more ... It's important to make the difference between the behaviour of a virtual creature and the potential functionality of an object composing the virtual world. For example, the potential functionality of a signpost is to inform, and of a door is to open itself in a specific way. ...
This paper presents a new architecture for simulating virtual humans in complex urban environment... more This paper presents a new architecture for simulating virtual humans in complex urban environments. Our approach is based on the integration of six modules. Four key modules are used in order to: manage environmental data, simulate human crowds, control interactions between virtual humans and objects, and generate tasks based on a rule-based behavioural model. The communication between these modules are made through a Client/Server system. Finally, all lowlevel virtual human actions are delegated to a single motion and behavioural control module. Our architecture combines various human and object simulation aspects, based on the coherent extraction and classification of information from a virtual city database. This architecture is discussed in this paper, together with a detailled case-study example. RBBS CITY Router CROWD SMART OBJECT Controller Message-based communication function calls AGENTlib ACTION PERCEPTION Figure 1 -Representation of the system architecture
This paper investigates the use of 3D immersive virtual environments and 3D prints for interactio... more This paper investigates the use of 3D immersive virtual environments and 3D prints for interaction with past material culture over traditional observation without manipulation. Our work is motivated by studies in heritage, museum, and cognitive sciences indicating the importance of object manipulation for understanding present and ancient artifacts. While virtual immersive environments and 3D prints have started to be incorporated in heritage research and museum displays as a way to provide improved manipulation experiences, little is known about how these new technologies affect the perception of our past. This paper provides first results obtained with three experiments designed to investigate the benefits and tradeoffs in using these technologies. Our results indicate that traditional museum displays limit the experience with past material culture, and reveal how our sample of participants favor tactile and immersive 3D virtual experiences with artifacts over visual non-manipulative experiences with authentic objects.
Uploads
Papers by M. Kallmann