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Text File | 1995-01-30 | 8KB | 366 lines

ISL.BNF - Copyright (c) 1995 Grizzly Bear Labs, last modified 01-25-94 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. restage and islobjs both handle the entire 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 set of characters which is delimited by double quotes. A legal string may contain 0 or more of any characters except for the double quotes, since it is delimited by double quotes. 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. 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 LAYER U32, you have one keyword (CAMERA), the name (STRING), and a second keyword (LAYER) with the layer number (U32). 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" LAYER 0. 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 shadowflag which is either : (nothing) or SHADOW. 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. 8) File paths are stripped from file names by starting at the end of the string, and scanning backwards until either a \ or a / has been found. There are two possible subtle problems with this. One, if you have a PC stage and a / in your file name or an Amiga stage and a \ in your file name, truncation will occur. Two, ISL will not properly handle files located in a root directory or symbolic link unless they have a / or a \ in their path. Effect file names are case insensitive. Finally, here's the BNF: stage : stagehdr | stagehdr camera globals objects stagehdr : STAGE MAXFRAMES U32 LOOP U32 camera : camerahdr positions alignments sizes assocs effects camerahdr : CAMERA STRING LAYER U32 globals : globalhdr globalchunks positions alignments sizes globalhdr : GLOBALS STRING LAYER U32 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 objects : | objects object object : objecthdr fil3chunks positions alignments sizes assocs effects | lighthdr lit2chunks positions alignments sizes assocs | axishdr axischunks positions alignments sizes assocs objecthdr : OBJECT STRING LAYER U32 quickdrawflag lighthdr : LIGHT STRING LAYER U32 quickdrawflag axishdr : AXIS STRING LAYER U32 quickdrawflag positions : | positions pos2chunk | positions pth2chunk pos2chunk : POSITION frames xyz v0v1 splineflag knotflag pth2chunk : POSITION frames PATH STRING ACCEL U32 FLOAT DECEL U32 FLOAT alignments : | alignments aln2chunk | alignments palnchunk | alignments talnchunk aln2chunk : ALIGN frames xyz v0v1 splineflag knotflag palnchunk : ALIGN frames PATH yhorizontalflag gconformflag oconformflag talnchunk : ALIGN frames OBJECT STRING YROT FLOAT FLOAT sizes : | sizes osz2chunk osz2chunk : SIZE frames xyz v0v1 splineflag knotflag fil3chunks : | fil3chunks fil3chunk fil3chunk : ACTOR frames NAME STRING STATE STRING CYCLE FLOAT FLOAT reverseflag v0v1 splineflag knotflag lit2chunks : | lit2chunks lit2chunk lit2chunk : ACTOR frames ppshape rrshape shadowflag diminishflag rgb TRANSITION U32 flareflag axischunks : | axischunks axischunk axischunk : ACTOR frames assocs : | assocs asscchunk asscchunk : ASSOC frames OBJECT STRING effects : | effects effect effect : EFFECT U32 frames Baloon STRING radiustype FLOAT reverseflag returnflag | EFFECT U32 frames Boing20 STRING xyzaxis ucdsquash SHRINK FLOAT TIMES U32 | EFFECT U32 frames Boing2 STRING xyzaxis ucdsquash SHRINK FLOAT TIMES U32 | EFFECT U32 frames Explode STRING srlshape xyzaxis EXPLOSION FLOAT FLOAT SCALING FLOAT ROTATIONS FLOAT FLOAT SEED U32 returnflag reverseflag | EFFECT U32 frames Firewrks 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 sharpflag | EFFECT U32 frames Particle STRING dreflag bounceflag taperflag reverseflag returnflag TRAVEL FLOAT SCALING FLOAT FLOAT ROTATIONS FLOAT FLOAT HTIME FLOAT GRAVITY FLOAT SEED U32 ELASTICITY FLOAT ZTIME FLOAT ZGROUND FLOAT SPEED FLOAT ZANGLE FLOAT FLOAT XANGLE FLOAT FLOAT | EFFECT U32 frames Ripple STRING lrtoggle WAVELENGTH FLOAT ZAMP FLOAT TRAVEL FLOAT RIPPLES U32 | EFFECT U32 frames Rotate20 STRING xyzaxis DEGREES FLOAT | EFFECT U32 frames Rotate2 STRING xyzaxis DEGREES FLOAT | EFFECT U32 frames Sway STRING rxyzflag restrictflag GYRATIONS FLOAT FLOAT ANGLES FLOAT FLOAT SEED U32 | EFFECT U32 frames SPIKE STRING lcrflag DISTANCE FLOAT FLOAT CYCLES FLOAT FLOAT DISPERSION FLOAT SEED U32 restrictflag reverseflag returnflag | 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 v0v1 : VELOCITY FLOAT FLOAT xyzaxis : XAXIS | YAXIS | ZAXIS rzaxis : RANDOMAXIS | ZAXIS ucdsquash : +SQUASH | SQUASH | -SQUASH srlshape : SPHERICAL | RADIAL | LINEAR ppshape : POINT | PARALLEL rrshape : | ROUND | RECTANGULAR radiustype : INSCRIBE | OUTSCRIBE | AVERAGE | RADIUS sparkleflag : | SPARKLE startflag : STARTON | STARTOFF alignyflag : | ALIGNY keepxflag : | KEEPX mirrorflag : | MIRROR reverseflag : | REVERSE sharpflag : | SHARP returnflag : | RETURN lrtoggle : LINEAR | RADIAL shadowflag : | SHADOW diminishflag : | DIMINISH | FALLOFF yhorizontalflag : | YHORIZONTAL gconformflag : | GCONFORM oconformflag : | OCONFORM quickdrawflag : | QUICKDRAW splineflag : | SPLINE knotflag : | KNOT flareflag : | NOFLARE dreflag : | DELAYED | RAIN | EMISSION bounceflag : | BOUNCE taperflag : | TAPER lcrflag : LINEAR | CYLINDRICAL | RADIAL restrictflag : | RESTRICT rxyzflag : RANDOM | XAXIS | YAXIS | ZAXIS