中国科学院南京天文光学技术研究所机构知识库

The invention discloses a method for rendering on the basis  of hemispherical orthogonal function, the method compris­ ing the following steps: selecting rendering fragments and  establishing a local coordinate system; acquiring a bidirec­ tional reflectance distribution function of a material; if  global illumination is an orthogonal function, determining a  rotation matrix of an orthogonal function coefficient accord­ ing to the rotation angles of the global coordinate system and  the local coordinate system, and calculating a local orthogo­ nal function illumination coefficient; converting the local  orthogonal function illumination coefficient into a hemi­ spherical orthogonal function illumination coefficient; sampling to obtain the spatial distribution of a bidirectional  reflection distribution function of a rendered material;  obtaining a hemispherical orthogonal function of the bidi­ rectional reflection distribution function of the rendered  material; and using the dot product of a hemispherical  orthogonal function coefficient of illumination and a hemi­ spherical orthogonal function coefficient of the bidirectional  reflection distribution function of the rendered material and  accumulating to obtain the light intensity in the reflection  direction. A hemispherical harmonic function(HSH) is used  to fit measurement data or theoretically derived data of a  BRDF, which may avoid the difficulty of fitting that accurs  for a hemispherical harmonics function due to data being  missing in the lower hemisphere.