ITR: Volume Illustration: Non-Photorealistic Rendering of Volume Models

该项目研究通过体绘制将空间中每一点的信息可视化的过程。传统上，体绘制采用两种方法之一。第一种方法尝试对过程进行物理上的精确模拟，例如X射线穿过组织或光线穿过雾，从而产生体积数据的最逼真的视图(至少对于具有适当物理意义的数据)。第二种方法只是粗略地基于光的物理行为，而是使用空间中每个值的任意外观和空间中的累积过程来为可视化中的体积创建更广泛的外观。该项目提出了一种新的体绘制方法：使用非真实感绘制(NPR)技术来增强基于物理的绘制过程，以增强可视化的表现力。NPR从艺术和技术插图等领域获得灵感，开发出自动方法，从几何表面模型合成具有插图外观的图像。这种新的方法被称为体积插图，它结合了人们对基于物理的照明模型的熟悉程度，以及使用非照片级真实感渲染技术增强重要特征的能力。从技术上讲，该项目面临着几个挑战。在基于表面的NPR中，表面(特征)被很好地定义，而对于体积，体积特征区域通常是必须通过分析局部体积属性来确定的无定形区域。一旦识别了这些体积特征体积，就可以使用用户选择的参数特性来增强和说明它们。体积图提供了一个灵活的统一框架，通过放大特征、添加照明效果和应用程序纹理来增强体积模型的结构感知。体积插图将在预采样和程序定义的体积模型上工作，支持从实用的技术插图到更抽象的绘画效果的一系列图像样式。该项目将开发一系列体积插图技术，包括新颖的体积插图技术和将NPR技术改编和扩展到体积对象的技术。

This project studies the process of visualizing information at every point in space through volume rendering. Traditionally, volume rendering has employed one of two approaches. The first attempts a physically accurate simulation of a process such as X-rays passing through tissue or light passing through a fog, producing the most realistic views of volume data (at least for data with an appropriate physical meaning). The second approach is only loosely based on the physical behavior of light, using instead an arbitrary appearance of each value in space and an accumulation process through space to create a wider range of appearances for the volume in the visualization. This project proposes a new approach to volume rendering: the augmentation of a physics-based rendering process with non-photorealistic rendering (NPR) techniques to enhance the expressiveness of the visualization. NPR draws inspiration from such fields as art and technical illustration to develop automatic methods to synthesize images with an illustrated look from geometric surface models. The new approach, called volume illustration, combines the familiarity of a physics-based illumination model with the ability to enhance important features using non-photorealistic rendering techniques.Technically, the project faces several challenges. In surface-based NPR, the surfaces (features) are well defined, whereas with volumes, volumetric feature areas are often amorphous regions that must be determined through analysis of local volumetric properties. Once these volumetric feature volumes are identified, user selected parametric properties can be used to enhance and illustrate them. Volume illustration provides a flexible unified framework for enhancing structural perception of volume models through the amplification of features, the addition of illumination effects, and the application of procedural textures. Volume illustration will work on both presampled and procedurally defined volume models, enabling a range of image styles from practical technical illustrations to more abstract painterly effects. The project will develop a collection of volume illustration techniques, including novel volume illustration techniques and techniques that adapt and extend NPR techniques to volume objects.