Lighting Controls for Computer Cinematography

Ronen Barzel
Pixar

This paper appears in issue Volume 2, Number 1.
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Abstract

Lighting is an essential component of visually rich cinematographic images. However, the common computer graphics light source models, such as a cone-shaped spotlight, are not versatile enough for cinematographic-quality lighting. In this paper we describe the controls and features of a light source model for lighting computer graphics films. The model is based on generalized light cones, emphasizing independent control over the shape and texture of lights and shadows. While inspired by techniques of real-world cinematography, it is tailored to the needs and capabilities of computer graphics. The model has been used successfully in production over the past few years, to light many short works and the movie Toy Story.

Author Information

Ronen Barzel, Pixar, 1001 West Cutting Blvd., Richmond, CA 94804 ronen@pixar.com

Figures

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Figure 1. Cylinder and cube on the floor, torus in midair.

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Figure 2. Same as Figure 1, with a conical key light.

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Figure 3. Selection. Same as Figure 2, but the torus is unaffected by the key light.

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Figure 4. Shape. A superellipse profile is swept into a pyramid, which may be truncated or sheared.

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Figure 5. Rounded rectangle shape, as in Figure 4b.

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Figure 6. A sheared barn door light, as in Figure 4d.

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Figure 7. Same as Figure 5, but with soft edges (Figure 8).

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Figure 8. Nested pyramids define the soft edges in Figure 7.

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Figure 9. Same as Figure 2, but with a sharp cutoff.

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Figure 10. Same as Figure 2, but with a gradual cuton.

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Figure 11. Basic shadows.Same as Figure 2, but with shadows from the key light.

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Figure 12. Shadow selection.Same as Figure 11, but the cube casts no shadow.

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Figure 13. Cheated shadows.All light parameters are the same as in Figure 11, but the shadow directions have been cheated so that the torus slightly shadows the cylinder.

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Figure 14. Shared shadows.Same as Figure 11, but the key light shares its shadows with the fill lights.

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Figure 15. Faked shadow.Same as Figure 2, but with a blocker that casts a shadow.

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Figure 16. Shape trimming.Same as Figure 2, but a large blocker has been placed just in front of the rear wall to eliminate unwanted illumination of the wall.

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Figure 17. Projecting a matte image as a “cookie cutter” to get alternate light shapes (Figure 19).

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Figure 18. Projecting a matte image to get simulated shadows, here for a dappled-leaf effect (Figure 19).

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Figure 19. a b The matte images used in Figure 17 and Figure 18.

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Figure 20. Projecting a color image (the well-known mandrill) to get a slide effect.

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Figure 21. Intensity distribution across beam.

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Figure 22. Intensity falloff with distance.

Follow-up

[July, 1998] Larry Gritz (lg@pixar.com) wrote a shader “uberlight” based on the outline in this paper. Larry and Ronen presented this at the Siggraph ’98 course “Advanced Renderman”.

[September, 1998] Tal Lancaster used Larry’s shader to roughly mimic the figures of this paper.

BibTeX Entry

@article{Barzel97,
  author = "Ronen Barzel",
  title = "Lighting Controls for Computer Cinematography",
  journal = "journal of graphics, gpu, and game tools",
  volume = "2",
  number = "1",
  pages = "1-20",
  year = "1997",
}