ISL.BNF - Copyright (c) 1992 John T. Grieggs, last modified 10-28-92 Current ISL version - 1.0. This file describes the BNF for ISL, the Imagine Staging Language. BNF is Backus Naur Form, a formal method for describing the syntax of a language. It should be fairly clear from the BNF what is allowable and what is not. This is a non-trivial document - I suggest you use ISL.doc to get an idea of what ISL is and does and how it works, then play with the destage and restage programs, and only then attempt to grok the grammar. Before diving into the BNF, here are some things which are not in the BNF which are true of the ISL grammar. Feel free to ignore the regular expressions and references to flex - they are included for the advanced user and should not be needed to understand the language. 1) Whitespace is optional. You may have an entire stage on one line, or may start a new line between any two keywords. 2) STRING is a token which is bracketed by double quotes. A legal string may contain 0 or more of the characters [A-Za-z0-9\.\/\_\:]. Or, in English, any upper or lower case letter, any digit, period, forward slash, underscore, or colon. 3) U32 is a token which contains one or more digits. It may not have a decimal point nor a sign. {DIGIT}+ is the flex pattern used. 4) FLOAT is a token which contains an optional minus sign, one or more digits, a period, and zero or more digits. \-?{DIGIT}+\.{DIGIT}* is the flex pattern used. Note that while six digits after the decimal are always emitted by destage, zero or more are acceptable. More than five will bring you up against the Imagine rounding problems... 5) I have not attempted to spell out the meaning of each U32, FLOAT, and STRING, on the theory that their meanings should be obvious based on their position in the grammar. For example, in camerahdr, defined as CAMERA STRING, you have one keyword (CAMERA) and the name (STRING). In this case, STRING would be the name of the CAMERA from the first column of the Action editor. A typical value for this clause would be CAMERA "CAMERA". 6) : means definition, | provides alternates. Eh? Take the very first part of the BNF for an example. A stage may consist of a stagehdr OR a stagehdr followed by a camera followed by globals followed by objects. These, in turn, are defined individually. 7) Optional clauses contain an empty : clause followed by one or more | clauses. An example would be genlockflag which is either : (nothing) or GENLOCK. The grammar is riddled with these, so make sure you get it. A stage may have zero or more objects, each of which may have one or more positions, one or more alignments, etc. Finally, here's the BNF: stage : stagehdr | stagehdr camera globals objects stagehdr : STAGE MAXFRAMES U32 camera : camerahdr positions alignments sizes camerahdr : CAMERA STRING globals : globalhdr globalchunks positions alignments sizes globalhdr : GLOBALS STRING globalchunks : | globalchunks globalchunk globalchunk : ACTOR frames BRUSH STRING U32 BACKDROP STRING U32 AMBIENT rgb HORIZON rgb +ZENITH rgb -ZENITH rgb FOG btl FOG rgb STARFIELD FLOAT TRANSITION U32 SKYBLEND U32 genlockflag objects : | objects object object : objecthdr filechunks positions alignments sizes hinges effects | lighthdr litechunks positions alignments sizes hinges | axishdr axischunks positions alignments sizes hinges objecthdr : OBJECT STRING quickdrawflag lighthdr : LIGHT STRING axishdr : AXIS STRING positions : | positions posnchunk | positions pth2chunk posnchunk : POSITION frames xyz pth2chunk : POSITION frames PATH STRING ACCEL U32 FLOAT DECEL U32 FLOAT alignments : | alignments algnchunk | alignments palnchunk | alignments talnchunk algnchunk : ALIGN frames xyz palnchunk : ALIGN frames PATH yhorizontalflag talnchunk : ALIGN frames OBJECT STRING YROTATION FLOAT FLOAT sizes : | sizes osizchunk osizchunk : SIZE frames xyz filechunks : | filechunks filechunk filechunk : ACTOR frames NAME STRING CYCLE FLOAT FLOAT reverseflag TRANSITION U32 litechunks : | litechunks litechunk litechunk : ACTOR frames sccshape shadowflag diminishflag rgb TRANSITION U32 axischunks : | axischunks axischunk axischunk : ACTOR frames hinges : | hinges hingchunk hingchunk : HINGE frames OBJECT STRING effects : | effects effect effect : EFFECT U32 frames Boing2.0 STRING xyzaxis ucdsquash SHRINK FLOAT TIMES U32 | EFFECT U32 frames Fireworks STRING srlshape xyzaxis EXPLOSION FLOAT FLOAT SCALING FLOAT ROTATIONS FLOAT FLOAT EXPANSION FLOAT DISTANCE FLOAT SEED U32 sparkleflag | EFFECT U32 frames Flash STRING ON U32 OFF U32 startflag | EFFECT U32 frames Grow STRING YROT FLOAT XSCALE FLOAT ZSCALE FLOAT XTRANS FLOAT ZTRANS FLOAT alignyflag keepxflag mirrorflag reverseflag | EFFECT U32 frames Ripple STRING lrtoggle WAVELENGTH FLOAT ZAMP FLOAT TRAVEL FLOAT RIPPLES U32 | EFFECT U32 frames Rotate2.0 STRING xyzaxis DEGREES FLOAT | EFFECT U32 frames Tumble STRING rzaxis ROTATIONS FLOAT FLOAT SEED U32 frames : FRAMES U32 U32 xyz : XYZ FLOAT FLOAT FLOAT rgb : RGB FLOAT FLOAT FLOAT btl : BTL FLOAT FLOAT FLOAT xyzaxis : XAXIS | YAXIS | ZAXIS rzaxis : RANDOMAXIS | ZAXIS ucdsquash : +SQUASH | SQUASH | -SQUASH srlshape : SPHERICAL | RADIAL | LINEAR sccshape : SPHERICAL | CYLINDRICAL | CONICAL sparkleflag : | SPARKLE startflag : STARTON | STARTOFF alignyflag : | ALIGNY keepxflag : | KEEPX mirrorflag : | MIRROR reverseflag : | REVERSE lrtoggle : LINEAR | RADIAL shadowflag : | SHADOW diminishflag : | DIMINISH genlockflag : | GENLOCK yhorizontalflag : | YHORIZONTAL quickdrawflag : | QUICKDRAW