Milan Ikits

University of Utah, Salt Lake City, UT, United States

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Publications (16)3.02 Total impact

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    M. Ikits, C.D. Hansen
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    ABSTRACT: We present a method for combining multiple point-based constraints in haptic programming environments. Instead of using a single proxy point for haptic feedback, the method maintains a separate proxy for each constraint. The reaction force is computed by linking the proxies in a chain. Constraints are applied in sequential order, such that the proxy found in the current step becomes the probe for the next step in the chain. The advantage of the method over previous approaches is that the constraints are maintained precisely and the output is well-defined. We illustrate the method with examples from the domain of 3D scientific data visualization. Finally, we present the results of an experiment conducted to quantify the contribution of haptic guidance in two representative vector field exploration tasks.
    Haptic Interfaces for Virtual Environment and Teleoperator Systems, 2006 14th Symposium on; 04/2006
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    Charles D. Hansen, Milan Ikits
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    ABSTRACT: We present a method for combining multiple point-based constraints in haptic programming environments. Instead of using a single proxy point for haptic feedback, the method maintains a separate proxy for each constraint. The reaction force is computed by linking the proxies in a chain. Constraints are applied in sequential order, such that the proxy found in the current step becomes the probe for the next step in the chain. The advantage of the method over previous approaches is that the constraints are maintained precisely and the output is well-defined. We illustrate the method with examples from the domain of 3D scientific data visualization. Finally, we present the results of an experiment conducted to quantify the contribution of haptic guidance in two representative vector field exploration tasks.
    01/2006;
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    ABSTRACT: Harvesting the power of modern graphics hardware to solve the complex problem of real-time rendering of large unstructured meshes is a major research goal in the volume visualization community. While, for regular grids, texture-based techniques are well-suited for current GPUs, the steps necessary for rendering unstructured meshes are not so easily mapped to current hardware. We propose a novel volume rendering technique that simplifies the CPU-based processing and shifts much of the sorting burden to the GPU, where it can be performed more efficiently. Our hardware-assisted visibility sorting algorithm is a hybrid technique that operates in both object-space and image-space. In object-space, the algorithm performs a partial sort of the 3D primitives in preparation for rasterization. The goal of the partial sort is to create a list of primitives that generate fragments in nearly sorted order. In image-space, the fragment stream is incrementally sorted using a fixed-depth sorting network. In our algorithm, the object-space work is performed by the CPU and the fragment-level sorting is done completely on the GPU. A prototype implementation of the algorithm demonstrates that the fragment-level sorting achieves rendering rates of between one and six million tetrahedral cells per second on an ATI Radeon 9800.
    IEEE Transactions on Visualization and Computer Graphics 06/2005; 11(3):285-95. · 1.90 Impact Factor
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    ABSTRACT: We present a simple yet efficient calibration and registration procedure for improving the overall static display accuracy of the Visual Haptic Workbench. The procedure is used for precisely colocating the visual and haptic workspaces of the system and is divided into three stages. First, we calibrate and register the PHANToM to the display surface of the workbench. Second, we calibrate the tracking system by attaching a rigid extension between the tracker sensor and the PHANToM stylus. Third, we interactively find the remaining unknown display parameters including eye and hotspot offsets as well as a local reference frame. Initial evaluation of the approach indicates that it is possible to improve static display accuracy by at least an order of magnitude for this system.
    03/2004;
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    Milan Ikits, J. Dean Brederson
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    ABSTRACT: Introduction Haptic feedback is a promising interaction modality for a variety of applications. Successful examples include robot teleoperation [57], virtual prototyping [63], painting [4], and medical training [30, 55]. Graphical applications are augmented with force or tactile feedback for two reasons: 1. to increase the realism of the simulation and 2. to improve operator performance, as typically indicated by increased precision, reduced fatigue, and shorter task completion times. Even though a great variety of graphical visualization techniques have been developed in the past, e#ective display of complex multi-dimensional and multi-field datasets remains a challenging task. While the human visual system is excellent at interpreting two-dimensional images, understanding volumetric features is di#cult due to occlusion, clutter, and lack of spatial cues. Stereoscopic rendering, shadows, and proper illumination provide important depth cues that make volumetric feature discrimination
    01/2004;
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    ABSTRACT: We present a haptic rendering technique that uses directional constraints to facilitate enhanced exploration modes for volumetric datasets. The algorithm restricts user motion in certain directions by incrementally moving a proxy point along the axes of a local reference frame. Reaction forces are generated by a spring coupler between the proxy and the data probe, which can be tuned to the capabilities of the haptic interface. Secondary haptic effects including field forces, friction, and texture can be easily incorporated to convey information about additional characteristics of the data. We illustrate the technique with two examples: displaying fiber orientation in heart muscle layers and exploring diffusion tensor fiber tracts in brain white matter tissue. Initial evaluation of the approach indicates that haptic constraints provide an intuitive means or displaying directional information in volume data.
    Visualization, 2003. VIS 2003. IEEE; 11/2003
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    ABSTRACT: Volume rendering is a flexible technique for visualizing dense 3D volumetric datasets. A central element of volume rendering is the conversion between data values and observable quantities such as color and opacity. This process is usually realized through the use of transfer functions that are precomputed and stored in lookup tables. For multidimensional transfer functions applied to multivariate data, these lookup tables become prohibitively large. We propose the direct evaluation of a particular type of transfer functions based on a sum of Gaussians. Because of their simple form (in terms of number of parameters), these functions and their analytic integrals along line segments can be evaluated efficiently on current graphics hardware, obviating the need for precomputed lookup tables. We have adopted these transfer functions because they are well suited for classification based on a unique combination of multiple data values that localize features in the transfer function domain. We apply this technique to the visualization of several multivariate datasets (CT, cryosection) that are difficult to classify and render accurately at interactive rates using traditional approaches.
    Visualization, 2003. VIS 2003. IEEE; 11/2003
  • Article: Unknown
    [Show abstract] [Hide abstract]
    ABSTRACT: We present a haptic rendering technique that uses directional constraints to facilitate enhanced exploration modes for volumetric datasets. The algorithm restricts user motion in certain directions by incrementally moving a proxy point along the axes of a local reference frame. Reaction forces are generated by a spring coupler between the proxy and the data probe, which can be tuned to the capabilities of the haptic interface. Secondary haptic effects including field forces, friction, and texture can be easily incorporated to convey information about additional characteristics of the data. We illustrate the technique with two examples: displaying fiber orientation in heart muscle layers and exploring diffusion tensor fiber tracts in brain white matter tissue. Initial evaluation of the approach indicates that haptic constraints provide an intuitive means for displaying directional information in volume data.
    09/2003;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We present a simple yet efficient calibration and registration procedure for improving the overall static display accuracy of the Visual Haptic Workbench. The procedure is used for precisely colocating the visual and haptic workspaces of the system and is divided into three stages. First, we calibrate and register the PHANToM to the display surface of the workbench. Second, we calibrate the tracking system by attaching a rigid extension between the tracker sensor and the PHANToM stylus. Third, we interactively find the remaining unknown display parameters including eye and hotspot offsets as well as a local reference frame. Initial evaluation of the approach indicates that it is possible to improve static display accuracy by at least an order of magnitude for this system.
    09/2003;
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    ABSTRACT: In direct volume rendering, transfer functions map data points to optical properties such as color and opacity. We have found transfer functions based on the Gaussian primitive to be particularly useful for multivariate volumes, because they are simple and rely on a limited number of free parameters. We show how this class of transfer function primitives can be analytically integrated over a line segment under the assumption that data values vary linearly between two sampled points. Analytically integrated segment can then be composited using standard techniques.
    09/2003;
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    ABSTRACT: Today, scientists, engineers and medical researchers routinely use computers to simulate complex physical phenomena. Such simulations present new challenges for computational scientists, including the need to effectively analyze and visualize complex three-dimensional data. As simulations become more complex and produce larger amounts of data, the effectiveness of utilizing such high resolution data will hinge upon the ability of human experts to interact with their data and extract useful information. Here we describe recent work at the SCI Institute in large-scale scalar, vector and tensor visualization techniques. We end with a discussion of ideas for the integration of techniques for creating computational multi-field visualizations
    ACM SIGGRAPH Computer Graphics 11/2001; 35(4):5–9. · 1.13 Impact Factor
  • Source
    Milan Ikits
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    ABSTRACT: Multimodal visual haptic user interfaces can be made more effective by accurately colocating the workspaces of their components. We have developed a coregistration technique for pose measurement devices based on nonlinear least squares parameter estimation. A reduced quaternion parameterization is used for representing the orientation component of coordinate transformations, which avoids the numerical instability of traditional approaches. The method is illustrated with two examples: the colocation of a haptic device with a position tracker, and the coregistration of an optical and a magnetic tracking system. 1
    05/2001;
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    ABSTRACT: Electromagnetic trackers have many favorable characteristics but are notorious for their sensitivity to magnetic field distortions resulting from metal and electronic equipment in the environment. We categorize existing tracker calibration methods and present an improved technique for reducing the static position and orientation errors that are inherent to these devices. A quaternion-based formulation provides a simple and fast computational framework for representing orientation errors. Our experimental apparatus consists of a 6-DOF mobile platform and an optical position measurement system, allowing the collection of full-pose data at nearly arbitrary orientations of the receiver. A polynomial correction technique is applied and evaluated using a Polhemus Fastrak resulting in a substantial improvement of tracking accuracy. Finally, we apply advanced visualization algorithms to give new insight into the nature of the magnetic distortion field.
    Virtual Reality, 2001. Proceedings. IEEE; 04/2001
  • Christopher R. Johnson, Milan Ikits
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    ABSTRACT: Multimodal interfaces have been shown to increase user performance for a variety of tasks. We have been investigating the synergistic benefits of haptic scientific visualization using an integrated, semi-immersive virtual environment. The Visual Haptic Workbench provides multimodal interaction; immersion is enhanced by head and hand tracking, haptic feedback, and additional audio cues. We present the motivation, design and implementation of the prototype system and describe some challenges ahead in the context of questions to be answered. Preliminary results indicate that visualization combined with haptic rendering intuitively conveys the salient characteristics of scientific data.
    01/2001;
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    M. Ikits, J.M. Hollerbach
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    ABSTRACT: This work deals with closed-loop calibration methods where the robot endpoint is constrained to lie on a plane. Previously published calibration approaches are shown to have certain weaknesses. A new solution is given using DH and Hayati notations and standard nonlinear least squares optimization. The procedure is extended via the implicit loop method, which takes input noise into account. Pose selection is guided by the noise amplification index. Simulation and experimental results are presented for a PUMA 560 industrial manipulator and are compared to those obtained from an open-loop calibration procedure
    Robotics and Automation, 1997. Proceedings., 1997 IEEE International Conference on; 05/1997
  • Source
    Milan Ikits, Charles D. Hansen
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    ABSTRACT: Hardware-accelerated volume rendering techniques are limited by the available fragment processing capacity and on board texture memory of current GPUs. In this paper we investigate the utility of a focus and context interface for hardware-accelerated volume rendering by introducing an interactive lens that can provide finer detail within the region of interest through magnification and high-quality rendering, or can show different aspects of the data via a separate transfer function or rendering mode. In addi- tion, the focus and context decomposition can be used as a user-controlled mechanism for multiresolution rendering in time-critical applications. We show through several ex- amples that such an interface is a useful addition to exist- ing volume rendering implementations and provides a way for improved interaction with volumetric datasets.