The RenderMan Interface - Paul Bourke

C.2 RIB Binding
The RenderMan Interface Bytestream Protocol, abbreviated RIB, is a byte-oriented protocol
for specifying requests to the RenderMan Interface (RI) library. RIB permits clients of the
RenderMan Interface to communicate requests to a remote rendering service, or to save
requests in a file for later submission to a renderer. To satisfy the many different needs of
clients, the protocol is designed to provide both
• an understandable (potentially) interactive interface to a rendering server, and
• a compact encoded format that minimizes transmission time (and space when stored
in a file)
RIB also strives to minimize the amount of communication from a server to a client. This
is particularly important in the situation where no communication is possible; e.g., when
recording RIB in a file.
RIB is a byte stream protocol. That is, RIB interpreters work by scanning the input stream
one byte at a time. This implies interpreters should make no assumptions about data alignment.
The protocol is best thought of as a command language where tokens in the input
stream can be transmitted either as 7-bit ASCII strings or, optionally, as compressed binary
data. The ASCII interface provides a convenient interface for users to interactively communicate
with a rendering server and for developers to debug systems that generate RIB. The
binary encoding significantly compresses the data stream associated with an RI description
with an associated savings in communication overhead and/or file storage cost.
C.2.1
Syntax rules
RenderMan Interface Protocol requests are constructed from sequences of tokens. Tokens
are formed by the input scanner by grouping characters according to the RIB syntax rules
(described below). Other than requirements associated with delimiting tokens, RIB employs
a free format syntax.
Character set
The standard character set is the printable subset of the ASCII character set, plus the characters
space, tab, and newline (return or line-feed). Non-printing characters are accepted,
but are discouraged as they impair portability.
The characters space, tab, and newline are referred to as white space characters and are
treated equivalently (except when they appear in comments or strings). White space is
used to delimit syntactic constructs such as identifiers or numbers. Any number of consecutive
white space characters are treated as a single white space character.
The characters ‘”’, ’#’, ’[’, and ’]’ are special: they delimit syntactic entities. All other characters
are termed regular characters and may be used in constructing syntactic entities such as
identifiers and numbers.
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