计算机图形学北大光照模型

* 当来自光源和周围环境的入射光照射在景物表面上时，将有部分光被反射或透射； 在视线方向的反射或透射光，被观察者眼睛中的视觉细胞接收 人眼中的杆状及锥状细胞接收光线，产生视觉 * * Insulator:绝热体 * Fuchsine:品红 Cyan：青色 * 是一种对实际的简化性的近似 * 是一种比场景中物体小的多的光源的一种近似 * Ia is the intensity of the ambient light, assumed to be constant for all objects. The amount of ambient light reflected from an object's surface is determined by ka, the ambient-reflection coefficient, which ranges from 0 to 1. ka may be thought of as characterizing the material from which the surface is made * Dull:较暗的 Matte:不光滑的 latex paint：乳胶涂料 * For ambient light only produce “shading” mode, We consider direction light in most rendered scene * For ambient light only produce “shading” mode, We consider direction light in most rendered scene * Ideal diffuse reflectors reflect light according to Lambert's cosine law, (there are sometimes called Lambertian reflectors). * The angle between the surface normal and the incoming light ray is called the angle of incidence and we can express a intensity of the light in terms of this angle The Ilight term represents the intensity of the incoming light at the particular wavelength (the wavelength determines the light's color). kd is a constant between 0 and 1 and varies from one material to another. 接近1表示材料具有很好的反光特性 当物体仅仅处于环境光源中cos项为1 两个相反的项相互消去，于是仅仅剩下一个cos term * 抽象： 自然界的大多数物体为漫反射体。假设其为理想漫反射体 Lambert漫反射模型是针对理想漫反射体在点光源照射下的光反射规律 * 这两个概念:描述发光单元自行发光的能力 * 表示发光单元在固定方向的光的功率. * 表示被照射体接受光能的能力 * 如图所示的效果使用了“constant/flat shading”方法,针对每个多边形使用常数光亮度，因此真实感程度低。 * 图片选自清华大学数学学院信息科学专业，李鑫(硕士生？)学位论文：基于外存的海量三角网格模型的压缩，导师查红彬。 * 桔红色显示部分可以是常数，所以，亮度插值计算简化为一次加法。 * 不是Phong模型！ * 计算机图形学教程(修订版)唐荣锡等，科学出版社 Taylor-series expansion and triangular surface patches. In Computer Graphics by DONALD HEARN P526 XA1=(0 1 0)T XA2=(0 0 1)T xp1 yp1 1 X=(xp2 yp2 1) xp3 yp3 1 a2 A2=(b2) c2 * I(x,y)-I1=a(I2-I1)+b(I3-I1) * Recursive ray tracing extends the visible-surface ray-tracing algorithm introduced in the previous chapter to interleave the determination