The RenderMan Interface - Paul Bourke

RiExposure
RiQuantize ( RtToken type, RtInt one, RtInt min, RtInt max, RtFloat ditheramplitude )
Set the quantization parameters for colors or depth. If type is ”rgba”, then color and
opacity quantization are set. If type is ”z”, then depth quantization is set. The value
one defines the mapping from floating-point values to fixed point values. If one is 0,
then quantization is not done and values are output as floating point numbers.
Dithering is performed by adding a random number to the floating-point values before
they are rounded to the nearest integer. The added value is scaled to lie between
plus and minus the dither amplitude. If ditheramplitude is 0, dithering is turned off.
Quantized values are computed using the following formula:
value = round( one * value + ditheramplitude * random() );
value = clamp( value, min, max );
where random returns a random number between ±1.0, and clamp clips its first argument
so that it lies between min and max.
By default color pixel values are dithered with an amplitude of 0.5 and quantization
is performed for an 8-bit display with a one of 255. Quantization and dithering and
not performed for depth values (by default).
RIB BINDING
Quantize type one min max ditheramplitude
EXAMPLE
RiQuantize (RI RGBA, 2048, -1024, 3071, 1.0);
SEE ALSO
RiDisplay, RiImager
RiDisplay ( RtToken name, RtToken type, RtToken mode, ...parameterlist...)
Choose a display by name and set the type of output being generated. name is either
the name of a picture file or the name of the framebuffer, depending on type.
The type of display is the display format, output device, or output driver. All implementations
must support the type names ”framebuffer” and ”file”, which indicate
that the renderer should select the default framebuffer or default file format, respectively.
Implementations may support any number of particular formats or devices
(for example, ”tiff” might indicate that a TIFF file should be written), and may allow
the supported formats to be user-extensible in an implementation-specific manner.
The mode indicates what data are to be output in this display stream. All renderers
must support any combination (string concatenation) of ”rgb” for color (usually red,
green and blue intensities unless there are more or less than 3 color samples; see the
next section, Additional options), ”a” for alpha, and ”z” for depth values, in that order.
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