We present a method to accurately and efficiently perform perspective volumetric ray casting of uniform regular datasets, called Exponential-Region (ER) Perspective. Unlike previous methods which undersample, oversamp...
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We present a method to accurately and efficiently perform perspective volumetric ray casting of uniform regular datasets, called Exponential-Region (ER) Perspective. Unlike previous methods which undersample, oversample, or approximate the data, our method near uniformly samples the data throughout the viewing volume. In addition, it gains algorithmic advantages from a regular sampling pattern and cache-coherent read access, making it an algorithm well suited for implementation on hardware architectures for volume rendering. We qualify the algorithm by its filtering characteristics and demonstrate its effectiveness by contrasting its antialiasing quality and timing with other perspective ray casting methods.
The authors analyze different filters used for the voxelization of analytically described objects. They show that, when the voxel model is used for visualization, the filter design is related to the subsequent renderi...
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The authors analyze different filters used for the voxelization of analytically described objects. They show that, when the voxel model is used for visualization, the filter design is related to the subsequent rendering phase, namely the gradient estimation technique. The theoretical and experimental analyses show that, in order to avoid a systematic error in normal estimation, the density profile near the surface should be linearly proportional to the distance from the surface. Optimal thickness of this transient region has been estimated to be about 3 voxel units. Based on these results, they propose a technique for voxelization of arbitrary parametric surfaces, using a hierarchical subdivision of the 2D surface domain.
The paper presents a voxel-based animation technique which employs either a mass-spring model or a finite element model. Two volumetric objects, a voxelized chair and a scanned muscle, are used as case studies with th...
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The paper presents a voxel-based animation technique which employs either a mass-spring model or a finite element model. Two volumetric objects, a voxelized chair and a scanned muscle, are used as case studies with the two different models. The mass-spring model is used to show an animation sequence of a falling and bouncing chair: wireframe display and volume rendering are used to display a real-time animation of the process. In addition, a real-time simulation is carried out by the finite element method (FEM) of a voxel-based multi-resolution muscle mesh. Two techniques, a direct integration and a simplified modal analysis method are discussed in the context of applying FEM for muscle deformation. Local deformation optimization with modal analysis for higher resolution muscle volumetric animation, which allows accurate prediction of muscle deformation changes, has been used. Physiological muscle force has been considered and a biomechanically-based 3D FEM muscle model has been implemented. Realistic animations have been produced based on the FEM simulation with various graphics techniques.
We present an efficient and robust ray-casting algorithm for directly rendering a curvilinear volume of arbitrarily-shaped cells. We designed the algorithm to alleviate the consumption of CPU power and memory space. B...
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We present an efficient and robust ray-casting algorithm for directly rendering a curvilinear volume of arbitrarily-shaped cells. We designed the algorithm to alleviate the consumption of CPU power and memory space. By incorporating the essence of the projection paradigm into the ray-casting process, we have successfully accelerated the ray traversal through the grid and data interpolations at sample points. Our algorithm also overcomes the conventional limitation requiring the cells to be convex. Application of this algorithm to several commonly-used curvilinear data sets has produced a favorable performance when compared with recently reported algorithms.
The authors present a multiresolution framework, called Multi-Tetra framework, that approximates volume data with different levels-of-detail tetrahedra. The framework is generated through a recursive subdivision of th...
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The authors present a multiresolution framework, called Multi-Tetra framework, that approximates volume data with different levels-of-detail tetrahedra. The framework is generated through a recursive subdivision of the volume data and is represented by binary trees. Instead of using a certain level of the Multi-Tetra framework for approximation, an error-based model (EBM) is generated by recursively fusing a sequence of tetrahedra from different levels of the Multi-Tetra framework. The EBM significantly reduces the number of voxels required to model an object, while preserving the original topology. The approach provides continuous distribution of rendered intensity or generated isosurfaces along boundaries of different levels-of-detail thus solving the crack problem. The model supports typical rendering approaches, such as marching cubes, direct volume projection, and splatting. Experimental results demonstrate the strengths of the approach.
3D virtual colonoscopy has recently been proposed as a non-invasive alternative procedure for the visualization of the human colon. Surface rendering is sufficient for implementing such a procedure to obtain an overvi...
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3D virtual colonoscopy has recently been proposed as a non-invasive alternative procedure for the visualization of the human colon. Surface rendering is sufficient for implementing such a procedure to obtain an overview of the interior surface of the colon at interactive rendering speeds. Unfortunately, physicians can not use it to explore tissues beneath the surface to differentiate between benign and malignant structures. In this paper, we present a direct volume rendering approach based on perspective ray casting, as a supplement to the surface navigation. To accelerate the rendering speed, surface-assistant techniques are used to adapt the resampling rates by skipping the empty space inside the colon. In addition, a parallel version of the algorithm has been implemented on a shared-memory multiprocessing architecture. Experiments have been conducted on both simulation and patient data sets.
In this paper we study the computational-space-based (C-space-based) ray-casting algorithm for rendering curvilinear volumes. With a simple counter example, we demonstrate that a proposed C-space-based method may not ...
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In this paper we study the computational-space-based (C-space-based) ray-casting algorithm for rendering curvilinear volumes. With a simple counter example, we demonstrate that a proposed C-space-based method may not generate rendering results as accurately as ray-casting in the physical space. We also analyze what needs to be improved and discuss several other issues related to the C-space-based approach.
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