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Defining a View Volume

• Reduce degrees of freedom

• position the camera (and view plane)

• point it towards the area of interest

• rotate it about the barrel to define "up"

• define the field of view (wide angle, normal...)

• define the depth of field (not in PHIGS and equivalent real-time graphics libraries)

• tilt view plane if oblique projection

• define perspective or parallel projection

• We define coordinate systems in which to specify these parameters:

• position of camera = COP in perspective projection

• position of camera = "way out" along the PRP - CW line, in parallel projection

• area of interest = combination of VRP and CW (breaks the metaphor slightly)

• rotate to define "up" = VUP vector

• define field of view = pick umin, umax, vmin, vmax on view plane

• Tilt film plane = adjust VPN relative to PRP - CW.

Mathematics of Projections - 09 MAY 95

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