The RenderMan Interface - Paul Bourke

xmin = clamp (ceil ( xresolution*xmin ), 0, xresolution-1);
rxmax = clamp (ceil ( xresolution*xmax -1 ), 0, xresolution-1);
rymin = clamp (ceil ( yresolution*ymin ), 0, yresolution-1);
rymax = clamp (ceil ( yresolution*ymax -1 ), 0, yresolution-1);
These regions are defined so that if a large image is generated with tiles of abutting
but non-overlapping crop windows, the subimages produced will tile the display
with abutting and non-overlapping regions.
RIB BINDING
Cropwindow xmin xmax ymin ymax
Cropwindow [xmin xmax ymin ymax]
EXAMPLE
RiCropWindow (0.0, 0.3, 0.0, 0.5);
SEE ALSO
RiFrameAspectRatio, RiFormat
RiProjection ( RtToken name, ...parameterlist...)
The projection determines how camera coordinates are converted to screen coordinates,
using the type of projection and the near/far clipping planes to generate a
projection matrix. It appends this projection matrix to the current transformation matrix
and stores this as the screen transformation, then marks the current coordinate
system as the camera coordinate system and reinitializes the current transformation
matrix to the identity camera transformation. The required types of projection are
”perspective”, ”orthographic”, and RI NULL.
”perspective” builds a projection matrix that does a perspective projection along the
z-axis, using the RiClipping values, so that points on the near clipping plane project
to z = 0 and points on the far clipping plane project to z = 1. ”perspective” takes one
optional parameter, ”fov”, a single RtFloat that indicates he full angle perspective field
of view (in degrees) between screen space coordinates (-1,0) and (1,0) (equivalently
between (0,-1) and (0,1)). The default is 90 degrees.
Note that there is a redundancy in the focal length implied by this procedure and the
one set by RiDepthOfField. The focal length implied by this command is:
focallength = horizontalscreenwidth ( ) fov
verticalscreenwidth
/ tan 2
”orthographic” builds a simple orthographic projection that scales z using the RiClipping
values as above. ”orthographic” takes no parameters.
RI NULL uses an identity projection matrix, and simply marks camera space in situations
where the user has generated his own projection matrices himself using RiPerspective
or RiTransform.
This command can also be used to select implementation-specific projections or special
projections written in the Shading Language. If a particular implementation does
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