計算機圖形學北大光照模型

* 當來自光源和周圍環(huán)境的入射光照射在景物表面上時，將有部分光被反射或透射； 在視線方向的反射或透射光，被觀察者眼睛中的視覺細胞接收 人眼中的桿狀及錐狀細胞接收光線，產(chǎn)生視覺 * * Insulator:絕熱體 * Fuchsine:品紅 Cyan：青色 * 是一種對實際的簡化性的近似 * 是一種比場景中物體小的多的光源的一種近似 * 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:較暗的 Matte:不光滑的 latex paint：乳膠涂料 * 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 當物體僅僅處于環(huán)境光源中cos項為1 兩個相反的項相互消去，于是僅僅剩下一個cos term * 抽象： 自然界的大多數(shù)物體為漫反射體。假設(shè)其為理想漫反射體 Lambert漫反射模型是針對理想漫反射體在點光源照射下的光反射規(guī)律 * 這兩個概念:描述發(fā)光單元自行發(fā)光的能力 * 表示發(fā)光單元在固定方向的光的功率. * 表示被照射體接受光能的能力 * 如圖所示的效果使用了“constant/flat shading”方法,針對每個多邊形使用常數(shù)光亮度，因此真實感程度低。 * 圖片選自清華大學數(shù)學學院信息科學專業(yè)，李鑫(碩士生？)學位論文：基于外存的海量三角網(wǎng)格模型的壓縮，導師查紅彬。 * 桔紅色顯示部分可以是常數(shù)，所以，亮度插值計算簡化為一次加法。 * 不是Phong模型！ * 計算機圖形學教程(修訂版)唐榮錫等，科學出版社 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

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