ENDS 375

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ENDS 375

• Foundations of Visualization
• 12/1/05 Notes

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Image Synthesis

• Digital Compositing
• The most basic effects techniques
• Based on earlier optical and camera techniques

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Digital Compositing

• digitally manipulated combination of at least two
  source images to produce an integrated result

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Image Elements

• The source images
• From many possible sources
• real images, scanned images
• CGI images
• paintings
• stop motion animation

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Historical Techniques

• Optical Printers
• various corrections
• use of mattes
• blue-screen
• In-Camera Techniques
• Rear projection - Stop motion

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Compositing Issues

• Spatial resolution
• Color resolution/Color Spaces
• Quantizing (artifacts)
• File formats
• Image compression,

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Basic Image Manipulation

• Creating output images from input images
• Color manipulations
• levels, contrast, gamma, invert,
• Look-Up Table based

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Spatial Filters

• Convolutions
• kernels
• Blurring
• Sharpening,

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Geometric Transformations

• Panning
• Rotation
• Scale
• Warping
• Morphing
• Sampling based

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Basic Image Compositing

• Alpha or matte image (channel)
• Over operation
• Output AM B(1-M)
• Mixing operation
• Subtracting operation

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Basic Image Compositing

• In
• Output A Balpha
• Out
• Output A (1 - Balpha)
• Atop
• Output (A in B) over B

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Matte Creation

• Luminance based
• Chrominance based
• blue or green screen
• Difference based
• Garbage mattes
• Edge mattes

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Digital Painting

• Matte paintings
• Traveling mattes
• Wire removal

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Temporal Manipulations

• Temporal resolution
• Temporal artifacts
• Changing running time
• expanding
• compressing
• Film to Video (24 fps to 30 fps)

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Formats

• Film
• 16mm, 35mm, 65mm, 70mm
• aspect ratios, frame rates
• Video
• NTSC, PAL, SECAM, HDTV, digital

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Pixel Ratios

• Square pixels
• Non-square pixels
• Computation vs Display ratios
• Video interlaced fields

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Image Tracking

• Image element tracking
• Stabilizing a plate
• remove camera jitter
• Match Moves

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Workflow

• Compositing Interfaces
• Maintaining Quality
• Efficiency