Device and method for estimating a glossy part of radiation

• US 10,607,404 B2
• Filed: 02/15/2016
• Issued: 03/31/2020
• Est. Priority Date: 02/16/2015
• Status: Active Grant

• Current Assignee: Thomson Licensing (Vantiva SA)
• Original Assignee: Thomson Licensing (Vantiva SA)
• Inventors: Lecocq, Pascal, Sourimant, Gael, Marvie, Jean-Eudes
• Primary Examiner(s): Thompson, James A
• Assistant Examiner(s): Beard, Charles L
• Application Number:
  US15/044,083
• Publication Number:
  US 20160239998A1
• Time in Patent Office: 1,506 Days
• CPC Class Codes: G06T 1/20 Processor architectures; Processor configuration, e.g. pipelining
• CPC Class Codes: G06T 15/506 Illumination models
• CPC Class Codes: G06T 15/55 Radiosity
• CPC Class Codes: G06T 15/83 Phong shading

Abstract

The present invention relates to a glossy part of radiation is estimated coming from a surface illuminated by area light source(s) having source surface(s) (A) bounded by edge curves, by determining integrand function(s) representative of that glossy part. The latter corresponding to an integration of the integrand function along the edge curves. In this respect, the integrand function(s) is/are approximated by means of peak-shape function(s) having a known antiderivative over the edge curves, and the glossy part is computed from analytical expressions associated with integrations of the peak-shape function(s) along the edge curves. Such invention can offer efficient and accurate computation for specular part of reflection as well as glossy transmission, and is notably relevant to real-time rendering.

Claims

1. A device for processing and rendering scene data wherein the scene data include data for determining a glossy part of a radiation coming from a surface illuminated by at least one area light source having at least one polygonal source surface bounded by light edge curves, said light edge curves being straight lines, said device comprising at least one processor configured to:

for each of said light edge curves, determine at least one integrand function representative of a contribution of said light edge curve to said glossy part, said integrand function being based on a Phong reflection model,

for each of said light edge curves, approximate said at least one determined integrand function using at least one peak-shape function having a known antiderivative,

determine said glossy part from the known antiderivatives of each of said peak-shape functions along said edge curves, said glossy part corresponding to a summation of integrations of each of said integrand functions along each of said light edge curves,

wherein said radiation is scattered at a point towards an observer and is defined by a hemispherical integral over a solid angle sustained by said at least one polygonal source surface, and said at least one peak-shape function comprises an affine combination of a Lorentzian function and a Pearson function, and in that said integrand function having a tail value at a tail abscissa, said at least one processor is configured to determine said affine combination by using parameters representative of said tail value and said tail abscissa, and

output and render pixels of an image associated with said glossy part.

2. The device according to claim 1, wherein said at least one processor is configured to determine said glossy part when said glossy part is reflected by said illuminated surface.

3. The device according to claim 2, wherein said glossy part corresponds to a specular term of the Phong reflection model.

4. The device according to claim 1, wherein said at least one processor is configured to determine said glossy part coming from points of said illuminated surface, and said at least one integrand function depends on the positioning of said points with respect to said edge curves and on viewing directions with regard to said points.

5. The device according to claim 1, wherein said at least one integrand function having a maximal height at a peak abscissa and having a floor value at side abscissas, said at least one processor is configured to determine said integrand function by using parameters representative of said maximal height, peak abscissa, floor value and side abscissas.

6. The device according to claim 1, wherein said at least one integrand function having a maximal height and reaching a predefined ratio of said maximal height at a width abscissa, said at least one processor is configured to determine said integrand function by using parameters representative of said maximal height and width abscissa.

7. The device according to claim 6, wherein said at least one peak-shape function being parameterized with at least one adjustment parameter, said at least one processor is configured to determine said at least one adjustment parameter by using said parameters representative of said maximal height and width abscissa.

8. The device according to claim 1, wherein said at least one processor is configured to determine said integrand function by using a linear combination of said at least one peak-shape function in an untranslated form, in a rightward translated form, and in a leftward translated form.

9. The device according to claim 1, wherein said at least one peak-shape function comprises at least one of a Lorentzian function and a Pearson function.

10. The device according to claim 9, wherein said at least one peak-shape function comprises an affine combination of a Lorentzian function and a Pearson function, and in that said integrand function having a tail value at a tail abscissa, said at least one processor is configured to determine said affine combination by using parameters representative of said tail value and tail abscissa.

11. The device according to claim 1, wherein said device comprises a programmable rendering pipeline adapted to compute said glossy part.

12. A method for processing and rendering scene data wherein the scene data include data for determining a glossy part of a radiation coming from a surface illuminated by at least one area light source having at least one polygonal source surface bounded by light edge curves, said light edge curves being straight lines, wherein said method comprises:

for each of said light edge curves, determining at least one integrand function representative of a contribution of said light edge curve to said glossy part, said integrand function being based on a Phong reflection model, said glossy part corresponding to a summation of integrations of said integrand functions along said light edge curves,

for each light edge curve, approximating each of said determined at least one integrand function using at least one peak-shape function having a known antiderivative,

determining said glossy part from the known antiderivatives of each of said peak-shape functions, said glossy part corresponding to a summation of integrations of said determined integrand functions along said light edge curves,

wherein said radiation is scattered at a point towards an observer and is defined by a hemispherical integral over a solid angle sustained by said at least one polygonal source surface, and said at least one peak-shape function comprises an affine combination of a Lorentzian function and a Pearson function, and in that said integrand function having a tail value at a tail abscissa, said at least one processor is configured to determine said affine combination by using parameters representative of said tail value and said tail abscissa, and

outputting and rendering pixels of an image associated with said glossy part.

13. The method according to claim 12, wherein said glossy part is determined when said glossy part is reflected by said illuminated surface.

14. The method according to claim 13, wherein said glossy part corresponds to a specular term of the Phong reflection model.

15. The method according to claim 12, wherein said glossy part is determined as coming from points of said illuminated surface, and said at least one integrand function depends on the positioning of said points with respect to said edge curves and on viewing directions with regard to said points.

16. The method according to claim 12, wherein said at least one integrand function having a maximal height at a peak abscissa and having a floor value at side abscissas, said integrand function is determined by using parameters representative of said maximal height, peak abscissa, floor value and side abscissas.

17. The method according to claim 12, wherein said at least one integrand function having a maximal height and reaching a predefined ratio of said maximal height at a width abscissa, said integrand function is determined by using parameters representative of said maximal height and width abscissa.

18. The method according to claim 17, wherein said at least one peak-shape function being parameterized with at least one adjustment parameter, said at least one adjustment parameter is determined by using said parameters representative of said maximal height and width abscissa.

19. The method according to claim 12, wherein said integrand function is determined by using a linear combination of said at least one peak-shape function in an untranslated form, in a rightward translated form, and in a leftward translated form.

20. The method according to claim 12, wherein said at least one peak-shape function comprises at least one of a Lorentzian function and a Pearson function.

21. The method according to claim 20, wherein said at least one peak-shape function comprises an affine combination of a Lorentzian function and a Pearson function, and in that said integrand function having a tail value at a tail abscissa, the method further comprising determining said affine combination by using parameters representative of said tail value and tail abscissa.

22. A non-transitory processor readable medium having stored therein instructions for causing a processor to perform the method according to claim 12.