Visualization and MultiMedia Lab, Department of Informatics, University of Zürich, Switzerland.
IEEE Trans Vis Comput Graph. 2011 Dec;17(12):1795-802. doi: 10.1109/TVCG.2011.198.
Direct volume rendering has become a popular method for visualizing volumetric datasets. Even though computers are continually getting faster, it remains a challenge to incorporate sophisticated illumination models into direct volume rendering while maintaining interactive frame rates. In this paper, we present a novel approach for advanced illumination in direct volume rendering based on GPU ray-casting. Our approach features directional soft shadows taking scattering into account, ambient occlusion and color bleeding effects while achieving very competitive frame rates. In particular, multiple dynamic lights and interactive transfer function changes are fully supported. Commonly, direct volume rendering is based on a very simplified discrete version of the original volume rendering integral, including the development of the original exponential extinction into a-blending. In contrast to a-blending forming a product when sampling along a ray, the original exponential extinction coefficient is an integral and its discretization a Riemann sum. The fact that it is a sum can cleverly be exploited to implement volume lighting effects, i.e. soft directional shadows, ambient occlusion and color bleeding. We will show how this can be achieved and how it can be implemented on the GPU.
直接体绘制已经成为可视化体数据集的一种流行方法。尽管计算机的速度在不断提高，但在保持交互帧率的同时，将复杂的光照模型纳入直接体绘制仍然是一个挑战。在本文中，我们提出了一种新的基于 GPU 光线投射的直接体绘制高级光照方法。我们的方法具有方向性软阴影，考虑到散射，环境光遮挡和颜色渗色效果，同时实现非常有竞争力的帧率。特别是，完全支持多个动态灯光和交互式传输函数更改。通常，直接体绘制是基于原始体绘制积分的非常简化的离散版本，包括将原始指数衰减发展为 a 混合。与沿光线采样时形成乘积的 a 混合相反，原始指数衰减系数是一个积分，其离散化是黎曼和。事实证明，它是一个和，可以巧妙地利用它来实现体积光照效果，即软方向阴影、环境光遮挡和颜色渗色。我们将展示如何实现这一点，以及如何在 GPU 上实现它。
