The RenderMan Interface - Paul Bourke

This procedure sets the times at which the shutter opens and closes. min should be
less than max. If min==max, no motion blur is done.
RIB BINDING
Shutter min max
EXAMPLE
RiShutter (0.1, 0.9);
SEE ALSO
RiMotionBegin
4.1.2 Displays
The graphics state contains a set of parameters that control the properties of the display
process. The complete set of display options is given in Table 4.3, Display Options.
Rendering programs must be able to produce color, coverage (alpha), and depth images,
and may optionally be able to produce “images” of arbitrary geometric or shader-computed
data. Display parameters control how the values in these images are converted into a displayable
form. Many times it is possible to use none of the procedures described in this
section. If this is done, the rendering process and the images it produces are described in a
completely device-independent way. If a rendering program is designed for a specific display,
it has appropriate defaults for all display parameters. The defaults given in Table 4.3,
Display Options characterize a file to be displayed on a hypothetical video framebuffer.
The output process is different for color, alpha, and depth information. (See Figure 4.2,
Imaging Pipeline). The hidden-surface algorithm will produce a representation of the light
incident on the image plane. This color image is either continuous or sampled at a rate
that may be higher than the resolution of the final image. The minimum sampling rate can
be controlled directly, or can be indicated by the estimated variance of the pixel values.
These color values are filtered with a user-selectable filter and filterwidth, and sampled at
the pixel centers. The resulting color values are then multiplied by the gain and passed
through an inverse gamma function to simulate the exposure process. The resulting colors
are then passed to a quantizer which scales the values and optionally dithers them before
converting them to a fixed-point integer. It is also possible to interpose a programmable
imager (written in the Shading Language) between the exposure process and quantizer.
This imager can be used to perform special effects processing, to compensate for nonlinearities
in the display media, and to convert to device dependent color spaces (such as
CMYK or pseudocolor).
Final output alpha is computed by multiplying the coverage of the pixel (i.e., the subpixel
area actually covered by a geometric primitive) by the average of the color opacity
components. If an alpha image is being output, the color values will be multiplied by this
alpha before being passed to the quantizer. Color and alpha use the same quantizer.
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