Particle-based simulation techniques, like the discrete element method or molecular dynamics, are widely used in many research fields. In real-time explorative visualization it is common to render the resulting data using opaque spherical glyphs with local lighting only. Due to massive overlaps, however, inner structures of the data are often occluded rendering visual analysis impossible. Furthermore, local lighting is not sufficient as several important features like complex shapes, holes, rifts or filaments cannot be perceived well.To address both problems we present a new technique that jointly supports transparency and ambient occlusion in a consistent illumination model. Our approach is based on the emission-absorption model of volume rendering. We provide analytic solutions to the volume rendering integral for several density distributions within a spherical glyph. Compared to constant transparency our approach preserves the three-dimensional impression of the glyphs much better. We approximate ambient illumination with a fast hierarchical voxel cone-tracing approach, which builds on a new real-time voxelization of the particle data. Our implementation achieves interactive frame rates for millions of static or dynamic particles without any preprocessing. We illustrate the merits of our method on real-world data sets gaining several new insights.
Pressure Temperature Wind speed a) b) c) d) Figure 1: Hurricane Isabel data set shown in different plots. Left: scatterplot of x×y using our blur method. Top row: zoomed-in views of the two marked regions. a) and c) use our method. b) and d) use transparent splats for comparison. Bottom row: histograms of three relevant dimensions and the selected focus coordinates marked with red vertical lines. (cf. Sec. 5.2)
AbstractScatterplots directly depict two dimensions of multi-dimensional data points, discarding all other information. To visualize all data, these plots are extended to scatterplot matrices, which distribute the information of each data point over many plots. Problems arising from the resulting visual complexity are nowadays alleviated by concepts like filtering and focus and context. We present a method based on depth of field that contains both aspects and injects information from all dimensions into each scatterplot. Our approach is a natural generalization of the commonly known focus effects from optics. It is based on a multidimensional focus selection body. Points outside of this body are defocused depending on their distance. Our method allows for a continuous transition from data points in focus, over regions of blurry points providing contextual information, to visually filtered data. Our algorithm supports different focus selection bodies, blur kernels, and point shapes. We present an optimized GPU-based implementation for interactive exploration and show the usefulness of our approach on several data sets.
This paper presents a new hardware‐accelerated approach to the volumetric reconstruction of trees from photographs, based on the methods introduced by Reche‐Martinez et al. The system applies an adapted computed tomography (CT) procedure that uses a set of oriented photographs with known interior and exterior camera parameters for creating a 3D model of a tree, while requiring considerably fewer images than standard CT. As tomographic reconstructions are complex tasks that result in time‐consuming processes for high‐resolution volumes, the hitherto existing methods are improved and modified to allow an ideal parallelisation of the computations on graphics hardware. The paper delivers a detailed insight into the complete process of the reconstruction, from the acquisition and preparation of the input data to the implementation of the final system on graphics processing hardware.
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