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page. Remember, from Chapter 7, the different Renderman coordinate
systems: " raster " ® Physical Device Coordinates
(PDC) with 0, 0 at top left " screen" ® Normalized
Device Coordinates (NDC), but not restricted to 0.0 £ NDC ³ 1,
e.g., for a screen with an aspect ratio of 4:3 might have -1. 33
£ x ³ +1. 33, -1 £ y ³ 1. " camera " ® Left Handed
viewing space " world " ® World Device Coordinates
(WDC) ( Remember in Renderman the default is left handed but can
be set to either left or right handed) " object " ®
"modeling " device coordinates, i.e., space in which
object is defined (same units as WDC) Some of the output
parameters are set by the following: RiFormat ® horizontal &
vertical resolution in pixels & aspect ratio RiCropWindow ®
Window in WDC (image is clipped to this window) RiScreenWindow®
"viewport " RiProjection ® projection mode, e.g.,
orthogorophic or perspective and field of view (expressed as an
angle) Look at listing 8 -1 for a general viewing program
RiDisplay ® output device, e.g., the tiff file, the RiRGBA
parameter has the following psible values ( objects vs
background) coverage depth into | | Ri--RGBA ---> rgh, a, z
RiDisplay ----> type of output ---> upper left pixel of
image ( 0, 0 ) is placed at upper left of file or display ( can
be changed ) RiFormat ----> size of output in pixels &
aspect ratios width height Look at virtual camera model -- by
default camera is at origin lookign along + z axis if want elese
where must do a viewing transformation place 8 -- 2 . c | Look at
placecam.O ---> gives VRP, view direction, orientation (
--rume 8 -- 4. c ---> physcam.o can also have clipping Ri(
Lipping( near , far ) = 10 - 10 inri.h = 1038 where default
values near = epslon C > f ), far = -- minimum valid value for
perspective can change image size in several ways 1. for ---->
larger gives wide angle lens effect so objects are smaller
----> smaller gives telephoto lens effect so objects are
bigger main 8 -- 1 for = 90 main 8 -- 1 a for = 60 main 8 -- 1 b
for = 30 2. ScreenWindow ---> larger window gives smaller
image remember perspective projection ---> X, Y = +, - 1 only
visible part Might want to render only a part of frame theb use
RiCropWindow ( l, r, t, b ) between f
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