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.
In this paper we describe a simple and efficient ray casting engine that is suitable for the rapid exploration of irregular grids composed of tetrahedra cells, or other cell complexes where cells have been broken up i...
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In this paper we describe a simple and efficient ray casting engine that is suitable for the rapid exploration of irregular grids composed of tetrahedra cells, or other cell complexes where cells have been broken up into faces. In our method, in a preprocessing phase, all the cells are broken into their corresponding faces. Visibility determination is performed after all the faces have been transformed into screen space; here we compute for each pixel an ordered list of the stabbing boundary faces. The final phase is the actual ray casting, which is performed independently for each pixel, and is basically a walk in the cell complex inside each component of the stabbing ordered list. For color calculations, a simple analytical lighting model is applied to each intersection of ray and cell. Our algorithm is simple, and our implementation fast and robust.
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