Direct volume rendering is often used to compare different 3D scalar fields. The choice of the transfer function which maps scalar values to color and opacity plays a critical role in this task. We present a technique for the automatic optimization of a transfer function so that rendered images of a second field match as good as possible images of a field that has been rendered with some other transfer function. This enables users to see whether differences in the visualizations can be solely attributed to the choice of transfer function or remain after optimization. We propose and compare two different approaches to solve this problem, a voxel-based solution solving a least squares problem, and an image-based solution using differentiable volume rendering for optimization. We further propose a residual-based visualization to emphasize the differences in information content.

翻译：直接体绘制常被用于比较不同三维标量场。传递函数（将标量值映射为颜色与不透明度）的选择在此任务中起着关键作用。我们提出一种传递函数自动优化技术，使得第二个场的渲染图像能够尽可能匹配已通过某种传递函数渲染出的第一个场图像。这使用户能够判断可视化差异是否完全归因于传递函数选择，抑或是优化后仍然存在。我们提出并比较两种解决该问题的方法：基于体素的解法（通过最小二乘问题求解）和基于图像的解法（利用可微体绘制进行优化）。此外，我们提出基于残差的可视化方法，以突出信息内容差异。