CHS: Medium: Collaborative Research: Fast Photorealistic Computer Graphics Rendering of Non-Smooth Surfaces

计算机图形学在外观重要的材料和产品设计的虚拟视觉原型中的应用越来越广泛。 在显示器上使用图形渲染来取代物理原型可能会使新产品和设计更快、更便宜地推向市场。 但是这样的应用要求在具有更高分辨率的显示器上的特定真实的材料的外观的高保真度。 基本问题是，目前的光反射数学模型假设小于像素的细节可以被忽略，并由平滑平均值代替。 在高分辨率下，这种假设就不成立了;当你靠近看时，大多数材料开始出现嘈杂、颗粒状或闪闪发光。 但是简单地在模型中包含微观细节并继续使用传统的渲染方法将太慢。该项目将开发一系列方法来模拟亚像素细节的可见效果，而不会大大增加渲染图像的时间和费用。 这项研究的结果将推广广泛的材料模型在计算机图形学中使用，使他们在近距离观察下工作。 它将从根本上改变表面反射率的定义，并提供一套新的工具，用于实现和设计反射率的工业应用，包括汽车设计，虚拟样机，视觉效果和预测产品可视化。准确地渲染材料的外观一直是计算机图形学的中心问题。 随着当今越来越高的显示分辨率和要求精确再现特定材料的应用，材料建模的现状正在达到极限。 问题在于，建模表面反射率的标准方法，双向反射分布函数（BRDF），从根本上假设表面粗糙度远小于像素的尺度。 但是粗糙的表面，可以通过平滑的BRDF模型来建模，用于更远或更低分辨率的视图，当人们看得更近时，开始出现噪音，颗粒状或闪烁，并且单个散射元素的效果变得可见。 这在各种材料中产生“闪烁”或“闪光”，这些材料很难使用当前技术进行建模，包括汽车上使用的金属油漆，电子产品中流行的喷砂和拉丝金属饰面，以及注塑塑料上无处不在的纹理饰面，以及织物，木材饰面和木纹以及许多其他材料。 该项目将开发新的方法来考虑表面反射的反射模型，在其核心建立在空间和角度变化，而不假设小尺度的平滑度。 这些模型考虑了单个散射特征的可见效果，并且空间和角度细节随着观看和照明条件的变化而自然显现。提出了详细材料的几种数学表示，涵盖表面和次表面效果，以形成完整的端到端管道的核心，该管道跨越新的采集方法和渲染技术。

Computer graphics is finding growing application to virtual visual prototyping for the design of materials and products where appearance is important. Using graphics rendering on a display to replace physical prototypes could potentially make it faster and cheaper to bring new products and designs to market. But such applications demand high fidelity in the appearance of specific real materials on displays with ever-higher resolution. The fundamental problem is that current mathematical models for light reflection assume that details smaller than a pixel can be ignored, and replaced by smooth averages. At high resolutions this assumption breaks down; most materials start to appear noisy, grainy, or glittery as one looks closer. But to simply include microscopic detail in the model and continue with conventional rendering methods would be far too slow. This project will develop a range of methods to model the visible effects of sub-pixel details without greatly increasing the time and expense of rendering images. The results of this research will generalize a broad range of material models used in computer graphics so that they work under close-range observation. It will transform the field by fundamentally changing the definition of surface reflectance and by providing a suite of new tools for implementing and designing reflectance in industrial applications including automotive design, virtual prototyping, visual effects, and predictive product visualization.Accurately rendering the appearance of materials has always been a central problem of computer graphics. With today's ever-higher display resolutions, and applications demanding exact reproduction of specific materials, the status quo in material modeling is reaching its limits. The problem is that the standard approach to modeling surface reflectance, the Bi-directional Reflectance Distribution Function (BRDF), fundamentally assumes that surface roughness is far smaller than the scale of pixels. But rough surfaces, which can be modeled by smooth BRDF models for more distant or lower-resolution views, start to appear noisy, grainy, or glittery as one looks closer and the effects of individual scattering elements become visible. This produces "shimmering" or "glints" in a variety of materials that are difficult to model using current technology, including metallic paints used on cars, bead-blasted and brushed metal finishes popular for electronics, and the ubiquitous textured finishes on injection-molded plastic, as well as in fabrics, wood finishes and wood grain, and many other materials. This project will develop new ways to think about surface reflection in terms of reflectance models that build in spatial and angular variation at their core, without assuming smoothness at small scales. These models account for the visible effects of individual scattering features, and spatial and angular detail emerges naturally as the viewing and illumination conditions reveal it. Several mathematical representations for detailed materials are proposed, covering both surface and subsurface effects, to form the core of a full end-to-end pipeline that spans new acquisition methods and rendering techniques.