Real-time 3D Composition Rendering Based On Ray-casting

With the rapid development of science and technology, visualization in scientific computing (VISC) has been widely applied in medicine, geological exploration, meteorology, molecular model and finite element analysis, etc. However, the visual effect of the image, which is reconstructed by traditional VISC algorithms, is too simple. We mainly focus on the three dimension image composition. We compose several reconstructed images together to reflect the internal features of volume intuitively.The main contributions of this paper are given as follows:To improve the speed and efficiency of the volume segmentation technology, an iso-surface volume segmenting technology based on ray-casting is proposed. While a light passes through the volume, the densities of each position are different. The volume can be segmented into several iso-surfaces by using this character. Experimental results show that the technology can not only render the volume in real-time but also segment the volume effectively.To reflect the spatial relationship of volume in the reconstructed image intuitively, a region compositing technology based on ray-casting is proposed. The volume segmented by iso-surface segmentation can be composited together to display. The focus region in the composited image is rendered in a manner of "fog" semi-transparency to give prominence to the internal structures of volume, and the context surface is rendered opaquely to show the external structures of volume. Experimental results show that the displaying mode can reflect the spatial relationship of volume visually.The traditional volume rendering algorithms only reconstruct the structures of volume by using single rendering mode, and it is difficult to display the complex internal features. To solve this problem, this paper approaches a two-level compositing technology based on ray-casting. Each structure of volume can be reconstructed by different rendering pass. Experimental results show that the composited image can reflect more internal information of volume.The compositing rendering technology based on ray-casting is realized by using graphic processing unit, which can render the volume in real-time. The composited image can intuitively reflect the spatial structures of volume, and reduce the analyzing complexity of the structure. This can be widely applied in computer-aided diagnosis.