CS 655 Advanced Computer Graphics

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CS 655 Advanced Computer Graphics

• Image Based Modeling and Rendering

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What is it?

• Image Based Modeling (IBM)
• using images to assist in modeling
• Image Based Rendering (IBR)
• using images to assist in rendering

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Traditional Graphics
Model
Image
Synthetic camera
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Traditional Computer Vision
Real Scene
Model
Real cameras
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Combined
Real Scene
Real cameras
Model
Synthetic Camera
Image
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Problem Vision Falls Short
Real Scene
Real cameras
Model
Synthetic Camera
Image
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As Does Graphics
Model
Synthetic Camera
Image
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Image Based Rendering
Real Scene
Real cameras
Model and images
Synthetic Camera
Image
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Image Based Modeling

• Images are used to determine
• Scene geometry
• Scene appearance
• Kinematic properties
• Reflectance characteristics
• Modeling photorealistic scenes is easier

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Image Based Rendering

• Appearance in available views is used to
  determine appearance in novel views
• Rendering is faster

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Is This New?

• Texture mapping
• Environment mapping
• Shadow maps
• Range images
• Etc.

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Models From Images

• How do we derive models from images?
• Camera calibration
• Structure from motion
• Stereo correspondence

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Camera Calibration

• If we know camera parameters, it is much easier
  to recover 3D information from the images
• Intrinsic parameters
• Focal length
• Radial distortion
• Extrinsic
• Position
• Orientation

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Structure From Motion

• An image consists of a set of points in 3D that
  have been projected to 2D
• If we take several images from different
  locations, and get a correspondence of points
  between images, we can deduce 3D locations

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Stereo Correspondence

• Take two images of a scene from positions close
  to one another
• Knowing the distance between camera positions
  (the baseline) we can determine 3D shape

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IBMR Papers
Light Field
Concentric Mosaics
Lumigraph
View Interpolation
View Morphing
Layered Depth Images
3D Warping
Texture Mapped Models
No Geometry
Implicit Geometry
Explicit Geometry
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Plenoptic Function

• Function which defines all light through a point
  in space
• with
• (Vx, Vy, Vz) the viewpoint
• q the azimuth angle
• f the elevation angle
• l the wavelength
• t the time

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Approximations to the Plenoptic Function