Perception of colour gradients in real and computer-simulated scenes: effects on depth

你能分辨出一个事件的真实的电影片段和计算机渲染的对应片段之间的区别吗？尽管动画和图形领域取得了巨大进步，但答案很可能是肯定的。在生成高质量的逼真渲染世界方面，我们还有很长的路要走，这些世界有着广泛的应用，从游戏到医疗和工业模拟器，再到建筑师设计的步行机，让我们感受到新建筑的外观。提高这种虚拟环境的自然性和真实性是计算机图形和渲染领域的一个关键挑战，特别是当需要交互式实时应用程序时：我们希望在模拟的新建筑中走动，而不仅仅是观看静态的场景。我们的进步缓慢的原因之一是，大多数人非凡的视觉能力，虽然看起来毫不费力，但隐藏着一个复杂的视觉处理网络，尚未完全理解。如果我们还不了解是什么增强了人类视觉系统的真实感，那么在开发技术以提高模拟的真实感方面进展缓慢也就不足为奇了。这项工作的目的是阐明一些基本的感知过程，这些过程是如何在颜色和亮度的微妙变化增强我们对三维场景的感知的真实性。这一人类行为研究为图形和渲染技术的发展奠定了基础，这些技术将为虚拟环境提供增强的真实感。这个问题如此困难的原因之一是，真实的世界包含非常复杂的光和颜色模式，这些模式以某种方式转化为我们对某物是绿色、亮、暗、近还是远的感知。例如，我面前桌子上的咖啡杯包含白色，明亮的镜面高光，有助于它看起来有光泽。也有反射的条纹表垫上，它坐，但我知道这些是反射，而不是图案的一部分马克杯。有一个附加的阴影，投下的光从窗口，我知道这不是我的杯子的一部分。表面的亮度和颜色都有变化，但我认为杯子是一种颜色，由一种材料制成。在这个项目中，我们将研究人类如何区分深度，光源和材料属性。对于大多数真实的场景，这是一个非常困难的计算问题，因为出现的特定局部补丁，例如，比周围的补丁更暗，可以具有它们由于各种原因而具有的值。例如，灰色文件柜的侧面可能与前面有非常不同的亮度，因为它在深度上远离你，并且与光源的角度不同，与橱柜的前面相比（实际上可能是不同的颜色）。人类的视觉系统是如何实现对一个坚实的、不变形的世界的连贯感知的，尽管视点和照明发生了变化？这是人类和计算机视觉研究中的一个巨大问题，对计算机图形学和虚拟环境开发有直接影响，但仍然知之甚少。我们将从探索包含孤立对象的非常简单的视觉场景开始，并研究颜色和亮度信息如何影响深度感知。这些数据将用于创建模型，预测亮度/颜色信息何时最有用。在其他实验中，我们将使用真实的物体和逼真的计算机渲染场景，这些场景保留了真实的世界中物体和光源之间的关系。我们的工作将为我们提供有关深度和场景感知的基本视觉机制的即时信息，这些信息直接通知计算机图形学和图像处理领域，为渲染场景看起来逼真所需的逼真亮度和颜色梯度提供指导。

Can you tell the difference between real filmed footage of an event, and a computer-rendered counterpart? Despite tremendous progress in animation and graphics, the answer is most likely yes. We still have a long way to go in generating high quality realistic rendered worlds, that have a wide variety of applications, from gaming, through medical and industrial simulators, to architect-designed walk-throughs that give us a feel for how a new building could look. Improving the naturalness and realism of such virtual environments is a key challenge for those involved in computer graphics and rendering, particularly when there is a demand for interactive, real-time applications: we want to walk around in that simulated new building, not just view static photograph-like scenes. One of the reasons that our progress is slow, is that the extraordinary visual capabilities of most humans, though apparently effortless, hide a complex web of visual processing that is not yet fully understood. If we do not yet understand what enhances realism for the human visual system, it is not surprising that progress is slow in developing technology to improve the realism of simulations. The aim of this work will be to elucidate some of the basic perceptual processes that underlie how subtle changes in colour and lightness enhance the realism of our perception of a three-dimensional scene. This human behavioural research underpins the development of graphics and rendering technologies that will deliver enhanced realism for virtual environments.One of the reasons why this problem is so hard is that the real world contains very complex patterns of light and colour that somehow translate into our perceptions of whether something is green, light, dark, near or far away. For example, my coffee cup on the table in front of me contains white, bright specular highlights that contribute to it looking glossy. There are also reflections of the stripy table mat on which it sits, yet I know these to be reflections, not part of the pattern on the mug. There is an attached shadow, cast by light from the window, and I know that is not part of my mug. And there are changes in lightness and colour across the surface, yet I see the mug as being a single colour, made from a single material. In this project we will study how humans distinguish between depth, light source, and material properties. For most real scenes, this is a very difficult computational problem because specific local patches that appear, for example, darker than those around them, can have the value they do for a variety of reasons. For example, the side of your grey filing cabinet may have a very different lightness than the front, because it slopes away from you in depth, and is at a different angle with the light source, compared with the front of the cabinet (and it could actually be a different colour). How does the human visual system achieve a coherent perception of a solid, non-deforming world, despite changes in view-point and lighting? This is a huge question in both human and computer vision research, with direct implications for computer graphics and virtual environment development, but one that is still poorly understood. We will start by exploring very simple visual scenes containing isolated objects, and study how colour and luminance information can influence depth perception. This data will be used to create models that predict when the luminance/colour information will be most useful. In other experiments we will use real objects and realistically computer-rendered scenes that preserve the relationship between objects and light source that would occur in the real world. Our work will give us immediate information about basic visual mechanisms of depth and scene perception that directly informs the fields of computer graphics and image processing, giving guidelines for when realistic luminance and colour gradients are required for a rendered scene to look realistic.