[清华大学co mputergraphic课件]chap3_final.pdfVIP

Computer Graphics Shi-Min Hu Tsinghua University BRDF 双向反射分布函数 ? BRDF – Bidirectional Reflectance Distribution Function – Describe how light is reflected from a surface ? Preliminary for BRDF ? BRDF ：definition and Properties ? BRDF Models ? BRDF Measurement Illumination 光照、照明 ? Illumination can be classified as local or global. – Local illumination is concerned with how Local illumination objects are directly illuminated by light sources. – Global illumination includes how objects are illuminated by light from locations other than light sources, Including by reflection of other objects and refraction through objects. Illumination 光照、照明 ? Illumination can be classified as local or global. – Local illumination is concerned with how objects are directly illuminated by light sources. – Global illumination includes how objects are Today’s Topic: a physical description of how illuminated by light from locations other than light is reflected from a surface, which is light sources, Including by reflection of other known as BRDF. objects and refraction through objects. Preliminary ? Before introducing BRDF, we review some preliminary concepts. – Spherical Coordinate 球面坐标 – Solid Angle 立体角 – Foreshortened Area 投影面积 – Radiant Energy 光能 – Radiant Flux 光通量 – Irradiance （辉度） – Intensity （发光强度） – Radiance （光亮度） Spherical Coordinate 球面坐标 ? Since light are mostly expressed in terms of directions, it is generally more convenient to describe them by spherical coordinates rather than by cartesian coordinate vectors. Spherical Coordinate 球面坐标 ? Since light are mostly expressed in terms of