US 11,989,823 B2
Method for rendering on basis of hemispherical orthogonal function
Yi Zheng, Jiangsu (CN); Kai Wei, Jiangsu (CN); Bin Liang, Jiangsu (CN); Ying Li, Jiangsu (CN); and Changpeng Ding, Jiangsu (CN)
Assigned to NANJING INSTITUTE OF ASTRONOMICAL OPTICS & TECHNOLOGY, NATIONAL ASTRONOMICAL OBSERVATORIES, CAS, Jiangsu (CN)
Appl. No. 17/775,531
Filed by NANJING INSTITUTE OF ASTRONOMICAL OPTICS & TECHNOLOGY, NATIONAL ASTRONOMICAL OBSERVATORIES, CAS, Jiangsu (CN)
PCT Filed Sep. 14, 2020, PCT No. PCT/CN2020/115055
§ 371(c)(1), (2) Date May 9, 2022,
PCT Pub. No. WO2021/063169, PCT Pub. Date Apr. 8, 2021.
Claims priority of application No. 201910938907.5 (CN), filed on Sep. 30, 2019.
Prior Publication US 2022/0406006 A1, Dec. 22, 2022
Int. Cl. G06T 15/50 (2011.01); G06T 15/20 (2011.01)
CPC G06T 15/506 (2013.01) [G06T 15/205 (2013.01)] 2 Claims
OG exemplary drawing
 
1. A method for rendering a three-dimensional image of a material on the basis of hemispherical orthogonal function, including the following steps:
S1: selecting a rendering tablet, and establishing a local coordinate system;
S2: getting a bidirectional reflection distribution function of the material;
S3: determining if global light is an orthogonal function; if it is, performing step S4 and S5; if not, proceeding to step S4′ and S5′;
S4: determining a rotation matrix of an orthogonal function coefficient according to a corner of a global coordinate system and the local coordinate system, and calculating a local orthogonal function of the local coordinate system;
S5: according to an equivalent formula, converting the local orthogonal function to the hemispherical orthogonal function; wherein the hemispherical orthogonal function includes a hemispherical harmonic function, a Zernike hemisphere function, and a vertical hemisphere function;
S4′: sampling an upper half of a ball, and obtaining a spatial distribution of light;
S5′: fitting light distribution with hemispherical orthogonal functions, obtaining a slime orthogonal function of the light;
S6: determining a direction of reflected light, and obtaining a spatial distribution of a two-way reflection distribution function of the material;
S7: fitting the two-way reflection distribution function of the material with the hemispherical orthogonal function, and obtaining a hemispherical orthogonal function factor of the two-way reflection distribution function of the material;
S8: multiplying a hemispherical orthogonal function coefficient of light by a half-way reflection distribution function of the material and accumulating light intensity of a reflection direction based on the multiplied hemispherical orthogonal function coefficient of light; and
S9: rendering the three-dimensional image of the material using the accumulated light intensity of the rejection direction.