In this article, we present a parallel prioritized Jacobian-based inverse kinematics algorithm fo... more In this article, we present a parallel prioritized Jacobian-based inverse kinematics algorithm for multithreaded architectures. We solve damped least squares inverse kinematics using a parallel line search by identifying and sampling critical input parameters. Parallel competing execution paths are spawned for each parameter in order to select the optimum that minimizes the error criteria. Our algorithm is highly scalable and can handle complex articulated bodies at interactive frame rates. We show results on complex skeletons consisting of more than 600 degrees of freedom while being controlled using multiple end effectors. We implement the algorithm both on multicore and GPU architectures and demonstrate how the GPU can further exploit fine-grain parallelism not directly available on a multicore processor. Our implementations are 10 to 150 times faster compared to a state-of-the-art serial implementation while providing higher accuracy. We also demonstrate the scalability of the algorithm over multiple scenarios and explore the GPU implementation in detail.
In this chapter we present a GPU implementation of the minimum spanning tree (MST) algorithm for ... more In this chapter we present a GPU implementation of the minimum spanning tree (MST) algorithm for undirected graphs. Our application follows Boruvka's approach to MST computation in a recursive manner and lays irregular data-dependent steps in terms of primitive operations using parallel scan, segmented scan, and split to achieve the reported high performance. The adaptation also provides an outlook on exploiting data-parallel primitives for nontrivial data-dependent algorithms.
IEEE Transactions on Visualization and Computer Graphics, Sep 1, 2007
Cluster-based tiled display walls can provide cost-effective and scalable displays with high reso... more Cluster-based tiled display walls can provide cost-effective and scalable displays with high resolution and large display area. Software to drive them needs to scale too if arbitrarily large displays are to be built. Chromium is a popular software API used to construct such displays. Chromium transparently renders any OpenGL application to a tiled display by partitioning and sending individual OpenGL primitives to each client per frame. Visualization applications often deal with massive geometric data with millions of primitives. Transmitting them every frame results in huge network requirements that adversely affects the scalability of the system. In this paper, we present Garuda, a client-server based display wall framework that uses off-the-shelf hardware and a standard network. Garuda is scalable to large tile configurations and massive environments. It can transparently render any application built using the Open Scene Graph (OSG) API to a tiled display without any modification by the user. The Garuda server uses an object-based scene structure represented using a scene graph. The server determines the objects visible to each display-tile using a novel adaptive algorithm which culls the scenegraph to a hierarchy of frustums. Required parts of the scenegraph are transmitted to the clients, which cache them to exploit the inter-frame redundancy. A multicastbased protocol is used to transmit the geometry to exploit the spatial redundancy present in tiled display systems. A geometry push philosophy from the server helps keep the clients in sync with one another. Neither the server nor a client needs to render the entire scene, making the system suitable for interactive rendering of massive models. Transparent rendering is achieved by intercepting the cull, draw, and swap functions of OSG and replacing them with our own. We demonstrate the performance and scalability of the Garuda system for different configurations of display wall. We also show that the server and network loads grow sub-linearly with increase in number of tiles which makes our scheme suitable to construct very large displays.
Background The authors had previouslydeveloped AnaVu, a low-resource 3D visualization tool for st... more Background The authors had previouslydeveloped AnaVu, a low-resource 3D visualization tool for stereoscopic projection of 3D models generated from annotated MRI neuroimaging data. However, its utility in neuroanatomical education needs to be quantified,and the students’ perspectives known. Methods A three-limb randomized controlled trial with crossover was designed. A sample (n=152) from the 2022 cohort of MBBS students at Government Medical College, Thiruvananthapuram (GMCT), was randomly selected from those who gave informed consent. After a one-hour introductory lecture on brainstem anatomy and a dissection session, students were randomized to three groups (S – stereo; M – Mono and C – Control). S was given a 20-minute demonstration on the brainstem lesson module in AnaVu in stereoscopic mode. M was given the same demonstration, but in monoscopic mode.The C group was taught using white-board drawn diagrams. Pre-intervention and post-intervention tests for four domains (basicrecal...
Computer displays have remained flat and rectangular for the most part. In this paper, we explore... more Computer displays have remained flat and rectangular for the most part. In this paper, we explore parametric display surfaces, which are of arbitrary shape, but with a mapping to a 2D domain for each pixel. The display could have arbitrary curved shapes given by implicit or parametric equations. We present a fast and efficient method to render 3D scenes onto such a display in a perspectively correct manner. Our method tessellates the scene based on the geodesic edge length and a user-defined error threshold. We also modify scene vertices, based on per-vertex ray casting, so that the final image appears correct to a user's viewpoint. The ray-surface intersection procedure, geodesic length computation and 2D image mapping are assumed to be known for the given surface. We exploit the tessellation hardware of the SM 5:0 GPUs to perform the error checking, polygon splitting, and rendering in a single pass. This brings the performance of our approach closer to rasterization schemes, w...
We present a method that uses a sketch-based interface in conjunction with a parallelized per-fra... more We present a method that uses a sketch-based interface in conjunction with a parallelized per-frame inverse kinematics (Parallel- PFIK) method for the purpose of motion editing. The artist creates and edits 3D constraints through an intuitive and easy to use 2D interface. These constraints are passed to Parallel-PFIK in order to solve for the joint angles of the character in a fast and efficient manner. Parallel-PFIK employs multicore processors and current generation GPUs extending parallel damped least squares inverse kinematics to multiple frames in order to solve the entire animation in real time. Our method allows users to create and edit 3D animations using an intuitive 2D sketch-based interface bringing 2D artist into 3D character animation.
Abstract. Visibility culling of a scene is a crucial stage for interactive graphics applications,... more Abstract. Visibility culling of a scene is a crucial stage for interactive graphics applications, particularly for scenes with thousands of objects. The culling time must be small for it to be effective. A hierarchical representation of the scene is used for efficient culling tests. However, when there are multiple view frustums (as in a tiled display wall), visibility culling time becomes substantial and cannot be hidden by pipelining it with other stages of rendering. In this paper, we address the problem of culling an object to a hierarchically organized set of frustums, such as those found in tiled displays and shadow volume computation. We present an adaptive algorithm to unfold the twin hierarchies at every stage in the culling procedure. Our algorithm computes from-point visibility and is conservative. The precomputation required is minimal, allowing our approach to be applied for dynamic scenes as well. We show performance of our technique over different variants of culling ...
Computer displays have remained flat and rectangular for the most part. In this paper, we explore... more Computer displays have remained flat and rectangular for the most part. In this paper, we explore parametric display surfaces, which are of arbitrary shape, but with a mapping to a 2D domain for each pixel. The display could have arbitrary curved shapes given by implicit or parametric equations. We present a fast and efficient method to render 3D scenes onto such a display in a perspectively correct manner. Our method tessellates the scene based on the geodesic edge length and a user-defined error threshold. We also modify scene vertices, based on per-vertex ray casting, so that the final image appears correct to a user’s viewpoint. The ray-surface intersection procedure, geodesic length computation and 2D image mapping are assumed to be known for the given surface. We exploit the tessellation hardware of the SM 5.0 GPUs to perform the error checking, polygon splitting, and rendering in a single pass. This brings the performance of our approach closer to rasterization schemes, witho...
Abstract—Displays have remained flat and passive amidst the many changes in their fundamental tec... more Abstract—Displays have remained flat and passive amidst the many changes in their fundamental technologies. One natural step ahead is to create displays that merge seamlessly in shape and appearance to one’s natural surroundings. In this paper, we present a system to design, render to, and build view-dependent multiplanar displays, of arbitrary shape built using planar, polygonal facets. Our system provides high quality, interactive rendering of 3D environments to a head-tracked viewer on arbitrary planar display shapes. We develop a novel rendering scheme that creates exact image and depth at each display facet. The facets thus align exactly at boundaries without inconsistencies in comparison with existing methods. Our approach scales well to large numbers of display facets. This is achieved using a single-pass rendering of all facets using a parallel, per-frame, viewdependent binning and prewarping of scene triangles. The method places no constraints on the scene or display and al...
The Graphics Processing Units (GPUs) provide high computation power at a low cost and is an impor... more The Graphics Processing Units (GPUs) provide high computation power at a low cost and is an important compute accelerator with a massively multithreaded architecture. In this paper, we present fast implementations of common graph operations like breadth-first search, st-connectivity, single-source shortest path, all-pairs shortest path, minimum spanning tree, and maximum flow for undirected graphs on the GPU using the CUDA programming model. Our implementations exhibit high performance, especially on large graphs. We use two data-parallel programming methodologies for these algorithms. One is an iterative, mask-based approach that processes valid data elements like vertices and edges using independent threads for each. The other is a divide-and-conquer approach that reduces the problem into smaller problems that are handled later using the same approach. Parallel algorithms for such problems have been reported in the literature before, especially on supercomputers. The massively mul...
Abstract: Computer displays have remained flat and rectangular for the most part. In this paper, ... more Abstract: Computer displays have remained flat and rectangular for the most part. In this paper, we explore parametric display surfaces, which are of arbitrary shape, but with a mapping to a 2D domain for each pixel. The display could have arbitrary curved shapes given by implicit or parametric equations. We present a fast and efficient method to render 3D scenes onto such a display in a perspectively correct manner. Our method tessellates the scene based on the geodesic edge length and a user-defined error threshold.
We present a method that uses a sketch-based interface in conjunction with a parallelized per-fra... more We present a method that uses a sketch-based interface in conjunction with a parallelized per-frame inverse kinematics (Parallel-PFIK) method for the purpose of motion editing. The artist creates and edits 3D constraints through an intuitive and easy to use 2D interface. These constraints are passed to Parallel-PFIK in order to solve for the joint angles of the character in a fast and efficient manner. Parallel-PFIK employs multicore processors and current generation GPUs extending parallel damped least squares inverse kinematics to multiple frames in order to solve the entire animation in real time. Our method allows users to create and edit 3D animations using an intuitive 2D sketch-based interface bringing 2D artist into 3D character animation.
Displays remain flat and passive amidst the many changes in their fundamental technologies. One n... more Displays remain flat and passive amidst the many changes in their fundamental technologies. One natural step ahead is to create displays that merge seamlessly in shape and appearance with one's natural surroundings. In this paper, we present a system to design, render to, and build view-dependent multiplanar displays of arbitrary piecewise-planar shapes, built using polygonal facets. Our system provides high quality, interactive rendering of 3D environments to a head-tracked viewer on arbitrary multiplanar displays. We develop a novel rendering scheme that produces exact image and depth map at each facet, producing artifact-free images on and across facet boundaries. The system scales to a large number of display facets by rendering all facets in a single pass of rasterization. This is achieved using a parallel, perframe, view-dependent binning and prewarping of scene triangles. The display is driven using one or more target quilt images into which facet pixels are packed. Our m...
Cluster-based tiled display walls can provide cost-effective and scalable displays with high reso... more Cluster-based tiled display walls can provide cost-effective and scalable displays with high resolution and a large display area. The software to drive them needs to scale too if arbitrarily large displays are to be built. Chromium is a popular software API used to construct such displays. Chromium transparently renders any OpenGL application to a tiled display by partitioning and sending individual OpenGL primitives to each client per frame. Visualization applications often deal with massive geometric data with millions of primitives. Transmitting them every frame results in huge network requirements that adversely affect the scalability of the system. In this paper, we present Garuda, a client-server-based display wall framework that uses off-the-shelf hardware and a standard network. Garuda is scalable to large tile configurations and massive environments. It can transparently render any application built using the open scene graph (OSG) API to a tiled display without any modific...
Publisher Summary This chapter presents a graphical processing unit (GPU) implementation of the m... more Publisher Summary This chapter presents a graphical processing unit (GPU) implementation of the minimum spanning tree (MST) algorithm for undirected graphs. This application follows Boruvka's approach to MST computation in a recursive manner and lays irregular data-dependent steps in terms of primitive operations using parallel scan, segmented scan, and split to achieve the reported high performance. The use of efficient primitives to map the irregular aspects of the problem to the data-parallel architecture of these massively multithreaded architectures is central to performance obtained. Optimized primitives can provide high speed-ups on such architectures. The adaptation also provides an outlook on exploiting data-parallel primitives for nontrivial data-dependent algorithms. It is likely to see more general graph algorithms implemented using such primitives in the near future.
In this article, we present a parallel prioritized Jacobian-based inverse kinematics algorithm fo... more In this article, we present a parallel prioritized Jacobian-based inverse kinematics algorithm for multithreaded architectures. We solve damped least squares inverse kinematics using a parallel line search by identifying and sampling critical input parameters. Parallel competing execution paths are spawned for each parameter in order to select the optimum that minimizes the error criteria. Our algorithm is highly scalable and can handle complex articulated bodies at interactive frame rates. We show results on complex skeletons consisting of more than 600 degrees of freedom while being controlled using multiple end effectors. We implement the algorithm both on multicore and GPU architectures and demonstrate how the GPU can further exploit fine-grain parallelism not directly available on a multicore processor. Our implementations are 10 to 150 times faster compared to a state-of-the-art serial implementation while providing higher accuracy. We also demonstrate the scalability of the algorithm over multiple scenarios and explore the GPU implementation in detail.
In this chapter we present a GPU implementation of the minimum spanning tree (MST) algorithm for ... more In this chapter we present a GPU implementation of the minimum spanning tree (MST) algorithm for undirected graphs. Our application follows Boruvka's approach to MST computation in a recursive manner and lays irregular data-dependent steps in terms of primitive operations using parallel scan, segmented scan, and split to achieve the reported high performance. The adaptation also provides an outlook on exploiting data-parallel primitives for nontrivial data-dependent algorithms.
IEEE Transactions on Visualization and Computer Graphics, Sep 1, 2007
Cluster-based tiled display walls can provide cost-effective and scalable displays with high reso... more Cluster-based tiled display walls can provide cost-effective and scalable displays with high resolution and large display area. Software to drive them needs to scale too if arbitrarily large displays are to be built. Chromium is a popular software API used to construct such displays. Chromium transparently renders any OpenGL application to a tiled display by partitioning and sending individual OpenGL primitives to each client per frame. Visualization applications often deal with massive geometric data with millions of primitives. Transmitting them every frame results in huge network requirements that adversely affects the scalability of the system. In this paper, we present Garuda, a client-server based display wall framework that uses off-the-shelf hardware and a standard network. Garuda is scalable to large tile configurations and massive environments. It can transparently render any application built using the Open Scene Graph (OSG) API to a tiled display without any modification by the user. The Garuda server uses an object-based scene structure represented using a scene graph. The server determines the objects visible to each display-tile using a novel adaptive algorithm which culls the scenegraph to a hierarchy of frustums. Required parts of the scenegraph are transmitted to the clients, which cache them to exploit the inter-frame redundancy. A multicastbased protocol is used to transmit the geometry to exploit the spatial redundancy present in tiled display systems. A geometry push philosophy from the server helps keep the clients in sync with one another. Neither the server nor a client needs to render the entire scene, making the system suitable for interactive rendering of massive models. Transparent rendering is achieved by intercepting the cull, draw, and swap functions of OSG and replacing them with our own. We demonstrate the performance and scalability of the Garuda system for different configurations of display wall. We also show that the server and network loads grow sub-linearly with increase in number of tiles which makes our scheme suitable to construct very large displays.
Background The authors had previouslydeveloped AnaVu, a low-resource 3D visualization tool for st... more Background The authors had previouslydeveloped AnaVu, a low-resource 3D visualization tool for stereoscopic projection of 3D models generated from annotated MRI neuroimaging data. However, its utility in neuroanatomical education needs to be quantified,and the students’ perspectives known. Methods A three-limb randomized controlled trial with crossover was designed. A sample (n=152) from the 2022 cohort of MBBS students at Government Medical College, Thiruvananthapuram (GMCT), was randomly selected from those who gave informed consent. After a one-hour introductory lecture on brainstem anatomy and a dissection session, students were randomized to three groups (S – stereo; M – Mono and C – Control). S was given a 20-minute demonstration on the brainstem lesson module in AnaVu in stereoscopic mode. M was given the same demonstration, but in monoscopic mode.The C group was taught using white-board drawn diagrams. Pre-intervention and post-intervention tests for four domains (basicrecal...
Computer displays have remained flat and rectangular for the most part. In this paper, we explore... more Computer displays have remained flat and rectangular for the most part. In this paper, we explore parametric display surfaces, which are of arbitrary shape, but with a mapping to a 2D domain for each pixel. The display could have arbitrary curved shapes given by implicit or parametric equations. We present a fast and efficient method to render 3D scenes onto such a display in a perspectively correct manner. Our method tessellates the scene based on the geodesic edge length and a user-defined error threshold. We also modify scene vertices, based on per-vertex ray casting, so that the final image appears correct to a user's viewpoint. The ray-surface intersection procedure, geodesic length computation and 2D image mapping are assumed to be known for the given surface. We exploit the tessellation hardware of the SM 5:0 GPUs to perform the error checking, polygon splitting, and rendering in a single pass. This brings the performance of our approach closer to rasterization schemes, w...
We present a method that uses a sketch-based interface in conjunction with a parallelized per-fra... more We present a method that uses a sketch-based interface in conjunction with a parallelized per-frame inverse kinematics (Parallel- PFIK) method for the purpose of motion editing. The artist creates and edits 3D constraints through an intuitive and easy to use 2D interface. These constraints are passed to Parallel-PFIK in order to solve for the joint angles of the character in a fast and efficient manner. Parallel-PFIK employs multicore processors and current generation GPUs extending parallel damped least squares inverse kinematics to multiple frames in order to solve the entire animation in real time. Our method allows users to create and edit 3D animations using an intuitive 2D sketch-based interface bringing 2D artist into 3D character animation.
Abstract. Visibility culling of a scene is a crucial stage for interactive graphics applications,... more Abstract. Visibility culling of a scene is a crucial stage for interactive graphics applications, particularly for scenes with thousands of objects. The culling time must be small for it to be effective. A hierarchical representation of the scene is used for efficient culling tests. However, when there are multiple view frustums (as in a tiled display wall), visibility culling time becomes substantial and cannot be hidden by pipelining it with other stages of rendering. In this paper, we address the problem of culling an object to a hierarchically organized set of frustums, such as those found in tiled displays and shadow volume computation. We present an adaptive algorithm to unfold the twin hierarchies at every stage in the culling procedure. Our algorithm computes from-point visibility and is conservative. The precomputation required is minimal, allowing our approach to be applied for dynamic scenes as well. We show performance of our technique over different variants of culling ...
Computer displays have remained flat and rectangular for the most part. In this paper, we explore... more Computer displays have remained flat and rectangular for the most part. In this paper, we explore parametric display surfaces, which are of arbitrary shape, but with a mapping to a 2D domain for each pixel. The display could have arbitrary curved shapes given by implicit or parametric equations. We present a fast and efficient method to render 3D scenes onto such a display in a perspectively correct manner. Our method tessellates the scene based on the geodesic edge length and a user-defined error threshold. We also modify scene vertices, based on per-vertex ray casting, so that the final image appears correct to a user’s viewpoint. The ray-surface intersection procedure, geodesic length computation and 2D image mapping are assumed to be known for the given surface. We exploit the tessellation hardware of the SM 5.0 GPUs to perform the error checking, polygon splitting, and rendering in a single pass. This brings the performance of our approach closer to rasterization schemes, witho...
Abstract—Displays have remained flat and passive amidst the many changes in their fundamental tec... more Abstract—Displays have remained flat and passive amidst the many changes in their fundamental technologies. One natural step ahead is to create displays that merge seamlessly in shape and appearance to one’s natural surroundings. In this paper, we present a system to design, render to, and build view-dependent multiplanar displays, of arbitrary shape built using planar, polygonal facets. Our system provides high quality, interactive rendering of 3D environments to a head-tracked viewer on arbitrary planar display shapes. We develop a novel rendering scheme that creates exact image and depth at each display facet. The facets thus align exactly at boundaries without inconsistencies in comparison with existing methods. Our approach scales well to large numbers of display facets. This is achieved using a single-pass rendering of all facets using a parallel, per-frame, viewdependent binning and prewarping of scene triangles. The method places no constraints on the scene or display and al...
The Graphics Processing Units (GPUs) provide high computation power at a low cost and is an impor... more The Graphics Processing Units (GPUs) provide high computation power at a low cost and is an important compute accelerator with a massively multithreaded architecture. In this paper, we present fast implementations of common graph operations like breadth-first search, st-connectivity, single-source shortest path, all-pairs shortest path, minimum spanning tree, and maximum flow for undirected graphs on the GPU using the CUDA programming model. Our implementations exhibit high performance, especially on large graphs. We use two data-parallel programming methodologies for these algorithms. One is an iterative, mask-based approach that processes valid data elements like vertices and edges using independent threads for each. The other is a divide-and-conquer approach that reduces the problem into smaller problems that are handled later using the same approach. Parallel algorithms for such problems have been reported in the literature before, especially on supercomputers. The massively mul...
Abstract: Computer displays have remained flat and rectangular for the most part. In this paper, ... more Abstract: Computer displays have remained flat and rectangular for the most part. In this paper, we explore parametric display surfaces, which are of arbitrary shape, but with a mapping to a 2D domain for each pixel. The display could have arbitrary curved shapes given by implicit or parametric equations. We present a fast and efficient method to render 3D scenes onto such a display in a perspectively correct manner. Our method tessellates the scene based on the geodesic edge length and a user-defined error threshold.
We present a method that uses a sketch-based interface in conjunction with a parallelized per-fra... more We present a method that uses a sketch-based interface in conjunction with a parallelized per-frame inverse kinematics (Parallel-PFIK) method for the purpose of motion editing. The artist creates and edits 3D constraints through an intuitive and easy to use 2D interface. These constraints are passed to Parallel-PFIK in order to solve for the joint angles of the character in a fast and efficient manner. Parallel-PFIK employs multicore processors and current generation GPUs extending parallel damped least squares inverse kinematics to multiple frames in order to solve the entire animation in real time. Our method allows users to create and edit 3D animations using an intuitive 2D sketch-based interface bringing 2D artist into 3D character animation.
Displays remain flat and passive amidst the many changes in their fundamental technologies. One n... more Displays remain flat and passive amidst the many changes in their fundamental technologies. One natural step ahead is to create displays that merge seamlessly in shape and appearance with one's natural surroundings. In this paper, we present a system to design, render to, and build view-dependent multiplanar displays of arbitrary piecewise-planar shapes, built using polygonal facets. Our system provides high quality, interactive rendering of 3D environments to a head-tracked viewer on arbitrary multiplanar displays. We develop a novel rendering scheme that produces exact image and depth map at each facet, producing artifact-free images on and across facet boundaries. The system scales to a large number of display facets by rendering all facets in a single pass of rasterization. This is achieved using a parallel, perframe, view-dependent binning and prewarping of scene triangles. The display is driven using one or more target quilt images into which facet pixels are packed. Our m...
Cluster-based tiled display walls can provide cost-effective and scalable displays with high reso... more Cluster-based tiled display walls can provide cost-effective and scalable displays with high resolution and a large display area. The software to drive them needs to scale too if arbitrarily large displays are to be built. Chromium is a popular software API used to construct such displays. Chromium transparently renders any OpenGL application to a tiled display by partitioning and sending individual OpenGL primitives to each client per frame. Visualization applications often deal with massive geometric data with millions of primitives. Transmitting them every frame results in huge network requirements that adversely affect the scalability of the system. In this paper, we present Garuda, a client-server-based display wall framework that uses off-the-shelf hardware and a standard network. Garuda is scalable to large tile configurations and massive environments. It can transparently render any application built using the open scene graph (OSG) API to a tiled display without any modific...
Publisher Summary This chapter presents a graphical processing unit (GPU) implementation of the m... more Publisher Summary This chapter presents a graphical processing unit (GPU) implementation of the minimum spanning tree (MST) algorithm for undirected graphs. This application follows Boruvka's approach to MST computation in a recursive manner and lays irregular data-dependent steps in terms of primitive operations using parallel scan, segmented scan, and split to achieve the reported high performance. The use of efficient primitives to map the irregular aspects of the problem to the data-parallel architecture of these massively multithreaded architectures is central to performance obtained. Optimized primitives can provide high speed-ups on such architectures. The adaptation also provides an outlook on exploiting data-parallel primitives for nontrivial data-dependent algorithms. It is likely to see more general graph algorithms implemented using such primitives in the near future.
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