View-dependant shading normal adaptation

Patent metadata

Field	Value
Publication number	US-10565781-B2
Application number	US-201514875813-A
Country	US
Kind code	B2
Filing date	Oct 6, 2015
Priority date	Aug 20, 2015
Publication date	Feb 18, 2020
Grant date	Feb 18, 2020

Abstract

A method of adjusting a shading normal vector for a computer graphics rendering program. Calculating a normalized shading normal vector pointing outwards from an origin point on a tessellated surface modeling a target surface to be rendered. Calculating a normalized outgoing reflection vector projecting from the origin point for an incoming view vector directed towards the origin point and reflecting relative to the normalized shading normal vector. Calculating a correction vector such that when the correction vector is added to the normalized outgoing reflection vector a resulting vector sum is yielded that is equal to a maximum reflection vector, wherein the maximum reflection vector is on or above the tessellated surface. Calculating a normalized maximum reflection vector by normalizing a vector sum of the correction vector plus the maximum reflection vector. Calculating a normalized adjusted shading normal vector by normalizing a vector difference of the normalized maximum reflection vector minus the incoming view vector.

First claim

What is claimed is:

1. A method of adjusting a shading normal vector for a computer graphics rendering program, comprising:
calculating a normalized shading normal vector pointing outwards from an origin point on a tessellated surface modeling a target surface to be rendered;
calculating a normalized outgoing reflection vector projecting from the origin point for an incoming view vector directed towards the origin point and reflecting relative to the normalized shading normal vector;
calculating a correction vector such that when the correction vector is added to the normalized outgoing reflection vector a resulting vector sum is yielded that is equal to a maximum reflection vector, wherein the maximum reflection vector is on or above the tessellated surface;
calculating a normalized maximum reflection vector by normalizing a vector sum of the correction vector plus the maximum reflection vector;
calculating a normalized adjusted shading normal vector by normalizing a vector difference of the normalized maximum reflection vector minus the incoming view vector; and
applying the normalized adjusted shading normal vector to shade the tessellated surface for rendering a computer graphics image to minimize visual artifacts in the computer graphics image.

2. The method of claim 1 , wherein calculating the correction vector includes:
calculating a length A between the tessellated surface and the normalized outgoing reflection vector, wherein the length A equals an absolute value of a dot product of the normalized outgoing reflection vector and a normalized geometric normal vector projecting from the point of origin;
calculating a length B of a projection of the normalized shading normal vector onto the normalized geometric normal vector, wherein the length B equals an absolute value of a dot product of the normalized shading normal vector and the normalized geometric normal vector; and
calculating a product of the normalized shading normal vector multiplied by a correction ratio equal to or greater than A/B.

3. The method of claim 2 , wherein the correction ratio equals A/B.

4. The method of claim 2 , wherein the correction ratio is a value in a range between A/B and (2A)/B.

5. The method of claim 1 , wherein calculating the normalized shading normal vector includes applying an interpolation heuristic to vertex normals of the tessellated surface.

6. The method of claim 5 , wherein the interpolation heuristic includes a Phong interpolation heuristic.

7. The method of claim 5 , wherein the interpolation heuristic includes a Blinn-Phong interpolation heuristic.

8. A non-transitory computer-readable storage medium storing instructions that, when executed by a processor, cause the processor to compute an adjusted shading normal vector, comprising:
calculating a normalized shading normal vector pointing outwards from an origin point on a tessellated surface modeling a target surface to be rendered;
calculating a normalized outgoing reflection vector projecting from the origin point for an incoming view vector directed towards the origin point and reflecting relative to the normalized shading normal vector;
calculating a correction vector such that when the correction vector is added to the normalized outgoing reflection vector a resulting vector sum is yielded that is equal to a maximum reflection vector, wherein the maximum reflection vector is on or above the tessellated surface;
calculating a normalized maximum reflection vector by normalizing a vector sum of the correction vector plus the maximum reflection vector;
calculating a normalized adjusted shading normal vector by normalizing a vector difference of the normalized maximum reflection vector minus the incoming view vector; and
applying the normalized adjusted shading normal vector to shade the tessellated surface for rendering a computer graphics image to minimize visual artifacts in the computer graphics image.

9. The non-transitory storage medium of claim 8 further stores instructions to cause the processor to calculate the correction vector including:
calculating a length A between the tessellated surface and the normalized outgoing reflection vector, wherein the length A equals an absolute value of a dot product of the normalized outgoing reflection vector and a normalized geometric normal vector projecting from the point of origin;
calculating a length B of a projection of the normalized shading normal vector onto the normalized geometric normal vector, wherein the length B equals an absolute value of a dot product of the normalized shading normal vector and the normalized geometric normal vector; and
calculating a product of the normalized shading normal vector multiplied by a correction ratio equal to or greater than A/B.

10. The non-transitory storage medium of claim 9 , wherein the correction ratio equals A/B.

11. The non-transitory storage medium of claim 9 , wherein the correction ratio is a value in a range between A/B and (2A)/B.

12. The non-transitory storage medium of claim 8 , wherein calculating the normalized shading normal vector includes applying an interpolation heuristic to vertex normals of the tessellated surface.

13. The non-transitory storage medium of claim 12 , wherein the interpolation heuristic includes a Phong interpolation heuristic.

14. The non-transitory storage medium of claim 12 , wherein the interpolation heuristic includes a Blinn-Phong interpolation heuristic.

15. A computer graphics rendering system, comprising:
a non-transitory computer-readable storage medium;
a processor configured to execute instructions stored on the non-transitory computer-readable storage medium to compute an adjusted shading normal vector, including:
calculating a normalized shading normal vector pointing outwards from an origin point on a tessellated surface modeling a target surface to be rendered;
calculating a normalized outgoing reflection vector projecting from the origin point for an incoming view vector directed towards the origin point and reflecting relative to the normalized shading normal vector;
calculating a correction vector such that when the correction vector is added to the normalized outgoing reflection vector a resulting vector sum is yielded that is equal to a maximum reflection vector, wherein the maximum reflection vector is on or above the tessellated surface;
calculating a normalized maximum reflection vector by normalizing a vector sum of the correction vector plus the maximum reflection vector;
calculating a normalized adjusted shading normal vector by normalizing a vector difference of the normalized maximum reflection vector minus the incoming view vector; and
applying the normalized adjusted shading normal vector to shade the tessellated surface for rendering a computer graphics image to minimize visual artifacts in the computer graphics image.

16. The system of claim 15 , wherein the processor is configured to execute the instructions to calculate the correction vector including:
calculating a length A between the tessellated surface and the normalized outgoing reflection vector, wherein the length A equals an absolute value of a dot product of the normalized outgoing reflection vector and a normalized geometric normal vector projecting from the point of origin;
calculating a length B of a projection of the normalized shading normal vector onto the normalized geometric normal vector, wherein the length B equals an absolute value of a dot product of the normalized shading normal vector and the normalized geometric normal vector; and
calculating a product of the normalized sh

Assignees

• Nvidia Corp

Inventors

• Gautron Pascal
• van Antwerpen Dietger
• Waechter Carsten
• Raab Matthias

Classifications

• G06T17/20

  Finite element generation, e.g. wire-frame surface description, {tesselation} · CPC title

• G06T15/83 Primary

  Phong shading · CPC title

• G06T15/506

  Illumination models · CPC title