Method and apparatus for reproducing lighting effects in computer animated objects

• US 6,342,887 B1
• Filed: 11/18/1998
• Issued: 01/29/2002
• Est. Priority Date: 11/18/1998
• Status: Expired due to Fees

• Current Assignee: Earl Robert Munroe
• Original Assignee: Earl Robert Munroe
• Inventors: Munroe, Earl Robert
• Primary Examiner(s): Zimmerman, Mark
• Assistant Examiner(s): Sealey, Lance W.
• Application Number:
  US09/195,428
• Time in Patent Office: 1,168 Days
• Field of Search: 345/426, 345/419
• US Class Current: 345/426
• CPC Class Codes: G06T 15/50 Lighting effects
• CPC Class Codes: G06T 15/506 Illumination models

Abstract

A method and apparatus for reproducing real-world lighting effects in a computer animated object, in which a three dimensional virtual set is created in proportion to the physical set, optical parameters of each physical light source used on the real-world set are input into the model and qualified by effects such as dimming, filtration, diffusion, occlusion and attenuation to produce synthetic lighting of the virtual set. The camera lens transmission characteristics and film speed may also be incorporated into the virtual set parameters. The three dimensional computer animated object is positioned and oriented within the virtual set according to the position and orientation in which the visual effect is to appear in the cinematographic scene, and is thus synthetically ‘illuminated’ within the virtual set in exactly the manner that a physical object of the same shape in the physical set would be illuminated, to produce a computer animated object that exhibits lighting effects as would appear in a comparable physical object photographed through the same camera lens using the same film as used in the physical set. The invention thus eliminates most of the judgment required on the part of a visual effects artist trying to reproduce in a computer animated object the lighting effects used in a cinematographic scene, and thus significantly reduces the time required to integrate the visual effect object into the cinematographic scene. Inherent characteristics of many light sources, filters, cameras and films can be maintained in a database or look-up table and can thus be entered into the virtual set by reference to the actual light sources and camera used on the real-world set.

Claims

1. A method of reproducing in a three dimensional computer animated object lighting effects generated by light sources on a physical set, composing the steps of:

(a) inputting data corresponding to metric parameters of the physical set to generate a virtual set scaled in proportion to the physical set,

(b) inputting data corresponding to the positions and orientations of the light sources to generate synthetic light sources in the virtual set in positions and orientations corresponding to positions and orientations of corresponding physical light sources on the physical set

(c) calculating effective luminous intensity and effective colour component parameters of the physical light sources, including determining a peak luminous intensity of each physical light source,

(d) reducing the peak luminous intensity to account for transmission characteristics of a lens of the camera,

(e) reducing the peak luminous intensity to account for a shutter angle of the camera,

(f) reducing the peak luminous intensity to account for an exposure index of cinematographic film used in the camera,

(g) inputting data to position the computer animated object in the virtual set, and

(h) applying the effective luminous intensity and effective colour component parameters of the physical light sources to the data representing the synthetic light sources to reproduce in the virtual set lighting effects corresponding to those of the physical set to thereby generate lighting effects on the computer animated object which correspond to lighting effects in the physical set.

2. The method of claim 1 including the step of reducing the peak luminous intensity to account for dimming of each physical light source.

3. The method of claim 1 including the step of reducing the peak luminous intensity to account for filtration of each physical light source.

4. The method of claim 2 including the step of reducing the peak luminous intensity to account for a frame rate of the camera.

5. The method of claim 1 in which step (b) includes the step of determining a base colour temperature of each light source.

6. The method of claim 5 including the step of adjusting the colour temperature to account for dimming.

7. The method of claim 1 including the step of reducing the peak luminous intensity to account for a frame rate of the camera.

8. The method of claim 5 including the step of adjusting a colour of each synthetic light source to account for filtration.

9. The method of claim 5 including the step of adjusting a colour of each synthetic light source to account for a colour balance of film in the camera.

10. The method of claim 1 in which step (e) includes the step calculating an effective light value for each light source.

11. The method of claim 10 including the step of adjusting the effective light value to account for attenuation of each light source due to distance from each light source to the computer animated object.

12. The method of claim 10 including the step of adjusting the effective light value to account for attenuation of each light source due to an angle between an optical axis of each light source and a line between each light source and the computer animated object.

13. The method of claim 10 including the step of adjusting for diffusion of each light source to account for a focus of the light.

14. The method of claim 10 including the step of adjusting for diffusion of each light source to account for filtration.

15. The method of claim 10 including the step of adjusting for occlusion of each light source due to any opaque object disposed between each light source and the computer animated object.

16. A product produced according to the method of claim 1.

17. An apparatus for reproducing in a three dimensional computer animated object lighting effects produced by physical light sources on a physical set captured by a camera, comprising a computer having a computer monitor and software for:

a) generating data corresponding to metric parameters of the physical set to generate a virtual set scaled in proportion to the physical set,

b) generate data corresponding to positions and orientations of the light sources to generate synthetic light sources in the virtual set in positions and orientations corresponding to positions and orientations of corresponding physical light sources on the physical set,

(c) calculating effective luminous intensity and effective colour component parameters of the physical light sources, including determining a peak luminous intensity of each physical light source,

(d) reducing the peak luminous intensity to account for transmission characteristics of a lens of the camera,

(e) reducing the peak luminous intensity to account for a shutter angle of the camera,

(f) reducing the peak luminous intensity to account for an exposure index of cinematographic film used in the camera,

(g) generating a representation of the computer animated object in the virtual set, and

(h) applying the effective luminous intensity and effective colour component parameters of the physical light sources to tho data representing the synthetic light sources to reproduce in the virtual set lighting effects corresponding to those of the physical set to thereby generate lighting effects on the computer animated object which correspond to lighting effects in the physical set.

18. A computer program product for use with a device for producing a representation of a three dimensional computer animated object and generating therein lighting effects corresponding to lighting effects produced by physical light sources on a physical set captured by a camera, the computer program product comprising:

a) computer readable program code for causing a computer to generate a representation of a virtual set scaled in proportion to the physical set,

b) computer readable program code for causing a computer to generate synthetic light sources in the virtual set in positions and orientations corresponding to positions and orientations of corresponding physical light sources on the physical set,

(c) computer readable program code for causing a computer to calculate effective luminous intensity and effective colour component parameters of the synthetic light sources corresponding to effective luminous intensity and effective colour component parameters of the light sources,

(d) computer readable program code for causing a computer to reduce the peak luminous intensity to account for transmission characteristics of a lens of the camera,

(e) computer readable program code for causing a computer to reduce the peak luminous intensity to account for a shutter angle of the camera,

(f) computer readable program code for causing a computer to reduce the peak luminous intensity to account for an exposure index of cinematographic film used in the camera, and

(g) computer readable program code for applying the effective luminous intensity and effective colour component parameters to the data representing the synthetic light sources to reproduce in the virtual set lighting effects corresponding to those of the physical set to thereby generate lining effects on the computer animated object which correspond to lighting effects in the physical set.