Lighting and Cameras

1
Lighting and Cameras

• Eric Sedgwick

2
Visual Arts

• Painting
• Sculpture
• Photography
• Cinema
• Cartoons

3
References

• digital Lighting and Rendering
• Jeremy Birn, New Riders Publishing
• Some information available at http//www.3drender.
  com/
• Jeremy Engleman some nice renderings
• art.net/jeremy
• Chapters 7 and 8 of text

4
Lighting

• Real Lights
• sun, tungsten bulb, flourescent bulb, Interior
  lighting, sky, match, candle
• light bounces
• Cast shadows no choice
• Constraints on placement
• CG lights
• May or may not cast shadows
• local illumination
• fast, but no bounces
• Free placement
• global illumination, e.g., radiosity
• more realistic, but computationally expensive

5
Additive color
6
CG lighting

• How is the diffuse shading computed?
• Ray-tracing
• Z-buffer

7
Types of CG lights I

• Ambient light - universal light, added to
  everything
• Point or omnidirectional light
• Light emanates in all directions
• Spot light
• Omni light with barn doors
• Umbra, penumbra
• Use for illuminating a specific area
• softness, spread, falloff, attenuation

8
Types of CG lights II

• Infinite or directional light
• Simulates sunlight
• light vector
• Doesnt matter where you place it
• Area lights - light emitted from a surface,
  rectangle, sphere
• soft shadows
• portraits
• Expensive computationally

9
Lights in Max

• Default lights, one or two omnis (turn off when
  other lights are added)
• Omni
• Spot
• Directional
• Sunlight system
• Ambient (in rendering effects)
• By default, shadows are off

10
Lighting in Maya

• Default lights, a point light behind and above
  camera (turns off when other lights are added)
• Point lights
• Spot lights
• Directional
• Ambient
• Volume lights

11
Lighting Workflow

• Set up camera first
• start dark, no ambient light
• add light
• false color helps to detect contribution of
  various sources

12
3 Point lighting

• Key light
• Fill light
• Back light
• (Background lights)
• Each light may in fact be several

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Key light

• Main illumination
• Obvious source of light in the scene
• predominant (only?) shadow
• Brightest
• Typically above and at roughly a 45 degree angle
  in reference to camera

14
Fill light

• adds to overall illumination
• reveals detail, I.e. bump mapping
• Soften shadows
• Often does not cast shadows

15
backlight

• hair light
• Rim light
• separates subject from background
• important in black and white photography
• Usually less prominent effect in CG

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3 point lighting tutorial

• Jeremy Birns at http//www.3drender.com/

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Standard Lighting setup

• Key
• 15 to 45 degrees to side (left or right) of
  camera
• 15 to 45 degrees above camera
• Fill
• 15 to 60 degree to opposite side of camera
• 0 to 30 degrees above (often below key)
• Guidelines only could use others for dramatic
  effect
• Low-angle (spooky), above (raccoon eyes), side
  key (casts unflattering nose shadow)

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Key-to-Fill Ratio

• Key / fill -or- KeyFill
• Remember to count all lights
• Low, usually at least 21
• Reflected light, or multiple light sources
• Cloudy, hazy days. Scattered light
• Interiors with lots of reflective surfaces
• More cheerful
• High, e..g, 81 or more
• Dark scenes, e.g., night
• Suspense, drama

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Low Key-to-Fill, Jeremy Englemann
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High Key-to-Fill Ratio, Jeremy Englemann
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Shadows

• spatial relationships
• composition
• contrast
• indicating offscreen space

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Spatial RelationshipsGreg Gargett , Internet Ray
Tracing Competition
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Offscreen Space, Adam Murphy
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Shadow algorithms

• Raytracing
• Send ray to object, bounce ray to light
• z-buffer or depth-mapped
• shadow buffer
• I.e., render scene from perspective of light
• Should differentiate between
• Dark side of object, normal doesnt point to
  light
• Object truly in shadow, another object blocks
  light
• Shadows are expensive, either way

25
Shadow tricks
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Faking shadows

• Set up lights
• Add spot for shadow
• exclude object casting shadow
• make brightness negative
• Very cheap computationally
• Not so accurate, good for non-critical shadows

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Shadows only light

• Get lighting the way you want
• create light to cast shadow
• make it cast shadows
• duplicate shadow light
• turn brightness negative, same magnitude
• turn shadows off
• Good shadow control, not cheap

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Qualities of light

• softness
• intensity
• attenuation
• color

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Softness

• Hard light
• Focused, sharp shadows, clear point of origin
• Soft light
• Soft shadows
• More diffuse
• Emitted from an area rather than from a single
  point
• Area light, or simulated area lighthttp//www.bti
  nternet.com/d.s.w/Tutorials/pixtut3.htm

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Soft light

• Jeremy Englemann
• Simulated area lighting
• multiple lights with soft shadows

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Simulating an Area light

• Start with single light, get brightness right,
  use falloff
• Make multiple instances (e.g, say 5 at 20
  brightness of original)
• Cast shadows using z-buffer with soft edges
• MAX Turn up sample range in Shadow Map Params
• Maya Turn up DMap filter size
• Much cheaper than an area light

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Attenuation

• Brightness decreases with distance from
  lightillumination at object intensity /
  distance2
• CG attenuation
• None far away lights (that arent far away in
  your scene)
• Linear medium distance lights (that arent far
  away in your scene)
• Quadratic/Inverse square lights where they are
  supposed to be

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color temperature at 3DU.com
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Practical lights
35
Cameras
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Real Camera vs. CG camera

• Real Camera
• Lens
• Focus
• Amount of light
• Placement
• CG camera
• No lens
• Everything in focus (can blur)
• Fully adjustable light
• Flexible placement

37
Real Camera terms

• Focal length distance from lens to film
• Angle of view
• Focal point
• Depth of Field distance
• Aperture size of lens opening
• f-stops

38
Some Lenses

• Portrait
• 70mm, 19.2
• Telephoto
• 120mm, 10.5
• Super long, I.e. nature photography
• 200mm, 6.1
• Source Lee Sullivan

• Super Wide angle
• 15mm, 78.5
• Wide angle
• 30mm, 44.2
• Normal not too far from eye
• 50mm, 27.4

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Depth of Field

• Blur foreground (and maybe background)
• Deeper for longer focal length often focus at
  infinity
• Closeups could look unnatural if background is
  clear
• Deep shots could look unnatural if foreground is
  too clear (less of an issue)
• Used for narrative, tells you what to look at

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Types of Cameras

• Orthogonal
• Perspective
• Perspective view acts as a camera
• In Max, Can match camera to perspective view
• Select viewport
• Select camera
• Viewgtmatch camera to view
• Most CG cameras dont have a lens

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Pyramid of Vision

• Aka cone of vision
• Eye point
• Image plane
• Near clipping plane hither plane
• depth of field
• Far clipping plane yon plane

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Field elements

• Aspect ratio (proportion of height to width of
  the image) establish early
• Title safe area
• Action safe area
• In configure area for viewport

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Depth of field

• Portion of the pyramid that is in focus
• Binoculars
• Focus
• Applies to real cameras very strongly
• CG, usually has infinite depth of field,
  everything is in focus, not very realistic

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Camera Translations

• Dolly sideways motion
• Truck forward/backward motion
• Boom vertical motion
• Tracking shot camera follows action

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Camera Rotations

• about camera center, I.e., target moves
• Tilt forward/backward, rotate in horizontal
  axis
• Roll to side, rotate in depth axis
• Pan left/right, rotate in vertical axis
• about target, I.e., camera moves
• Orbit

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Lens Animations

• Zoom
• in for close up
• out widen field of view
• Rack focus
• Zoom that adjusts the focus from subject to
  another.
• Narrative tool. E.g., filming conversation

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Some Lenses

• Portrait
• 70mm, 19.2
• Telephoto
• 120mm, 10.5
• Super long, I.e. nature photography
• 200mm, 6.1
• Source Lee Sullivan

• Super Wide angle
• 15mm, 78.5
• Wide angle
• 30mm, 44.2
• Normal not too far from eye
• 50mm, 27.4

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Distance

• Close-up
• Strong perspective
• Can be disorienting
• Can be mysterious
• Medium
• Long
• Weak perspective
• Binoculars
• Can be objective

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Camera Lenses

• Practical vs. stylistic use
• Focal length is inversely related to the angle of
  view
• Distortion due to perspective increases when
  focal length decreases

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camera shots

• Low-angle High-angle Point of
  view

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camera shots
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Parallax

• Animation
• Close up motion appears faster than far away
  motion.

53
Camera and lights

• Caution while camera and lighting effects can be
  dramatic they can also be highly distracting.
• Cameras
• Animate cameras OR- objects not both
• Dont use lights recklessly. They increase
  rendering time dramatically, particularly shadow
  casting lights.

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Lights and Camera

• Citizen Kane
• Director Orson Welles
• Goodfellas
• Director Martin Scorsese

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Lights and Camera example, anibyte
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Cameras

• aperture
• lens effects
• motion blur
• shutter speed

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Framing

• rule of thirds
• graphic weight