Difference between revisions of "III/VC SCM"

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= Overall Format =
+
  (02 00 01)h + 32-bit offset    '''GOTO''' next header chunk
  (02 00 01)h + 32 bit int    Jump to second segment
+
  byte                           Target game ('l' - Liberty for III, 'm' - Miami for VC, unused at runtime)
  byte                         Padding
+
  32-bit int                  Number of cutscene starts (VC Mobile only, unused at runtime)
   (Global vars)             Space for variable saving
+
  (Cutscene start array)      32-bit offset of '''START_CUTSCENE''' command * 300 (VC Mobile only, unused at runtime)
  (02 00 01)h + 32 bit int    Jump to third segment
+
   (Global variable space)     Space for global variable storage (first global offset is 8, 1212 in VC Mobile)
  byte                         Segment id
+
  (02 00 01)h + 32-bit offset    '''GOTO''' next header chunk
   32 bit int                 Number of models
+
  byte                           Alignment (always 0, ignored)
   (model names)             24 byte model names * number of models(model 0 not used)
+
   32-bit int                   Number of used objects (always 1 in VC Mobile{{ref|*}})
  (02 00 01)h + 32 bit int    Jump to fourth segment
+
   (Used object array)         24-byte object name * number of used objects (first object name is empty and therefore unused)
  byte                         Segment id
+
  (02 00 01)h + 32-bit offset    '''GOTO''' main script space (third header chunk is compiled only in script multifile)
8 bytes                      Padding/mysterious, unused data
+
  byte                           Alignment (always 0, ignored)
32 bit int                  Number of missions
+
  32-bit int                  Main script size
   (mission addresses)       32 bit addresses * number of missions
+
  32-bit int                  Largest mission script size
  (MAIN code)                 MAIN section, equal to size defined earlier
+
  16-bit int                  Number of mission scripts (120 in total)
  (mission code)               The mission data, missions stored at offsets defined earlier
+
   16-bit int                  Number of exclusive mission scripts (possibly 1 in III, 2 in VC)
 +
  (Multi script array)         32-bit offset * number of mission scripts
 +
  (Main script space)           Space of main script (equal to size defined earlier)
 +
  (Mission scripts space)       Space of mission scripts (each one is stored at file offsets defined earlier)
  
= Main Section =
+
{{note|*}} Compiler-wise, the model names of level objects are picked directly from [[OBJS]] and [[TOBJ]] sections of the [[IDE]] files whose <code>IDE Filename</code> begins with <code>DATA\</code> in [[Gta.dat|gta_vc.dat]].
Made up of many opcodes one after the other. Opcodes are of the format:
 
TOpcode {
 
  Opcode[2]: Word; //Opocode number in word format
 
  Parameters: Array Of TParameter;
 
}
 
The number of parameters is specific for each opcode. The [http://vc-db.webtools4you.net/ opcode database] has all of the opcodes in VC, with their parameter numbers, and for most, a description of what they do.
 
Parameters are of the format:
 
TParameter {
 
  ParameterType[1]: Byte; //Says which type of parameter will follow
 
  ActualParameter: varies; //The actual parameter
 
}
 
The parameter types are as follows (but there are more in SA):
 
01: 32-bit int  (DWord)
 
02: global var  (Word)
 
03: local var    (Word)
 
04: 8-bit int    (Byte)
 
05: 16-bit int  (Word)
 
06: 4-byte float (Single)
 
[[Label]]s use the type 01 (although if they address is small enough using data types 04 and 05 will also work). Global and local vars can also be used for labels.
 
Global vars reference a position in the file much like a label. There is a space at the top of the scm file filled with 00's which is space reserved for global vars. This is divided into blocks of 4 bytes, each var taking up one of these blocks. In compiled form, the global vars each point to somewhere in that block (or should do as otherwise writing to it will modify the actual code).
 
== Example ==
 
//this code
 
0001: wait 8 ms
 
0002: jump $var1
 
0050: gosub 1@
 
0051: return
 
 
//compiles as:
 
01 00 04 08 //wait opcode (First 2 bytes = opcode, next byte = 04 the parameter type for 8-bit int, and 08 is the actual value)
 
02 00 02 18 00 // jump opcode. The 18 00 would mean that the global var is stored at address 0x0018
 
50 00 03 01 00 //the gosub opcode
 
51 00 //the return opcode (it has no parameters)
 
  
{{Script-stub}}
+
{{N|VC|III}}
 
+
[[Category:Mission Script]] [[Category:File Formats]]
[[Category:Mission Script]]
 

Latest revision as of 23:25, 12 January 2021

(02 00 01)h + 32-bit offset    GOTO next header chunk
byte                           Target game ('l' - Liberty for III, 'm' - Miami for VC, unused at runtime)
  32-bit int                   Number of cutscene starts (VC Mobile only, unused at runtime)
  (Cutscene start array)       32-bit offset of START_CUTSCENE command * 300 (VC Mobile only, unused at runtime)
  (Global variable space)      Space for global variable storage (first global offset is 8, 1212 in VC Mobile)
(02 00 01)h + 32-bit offset    GOTO next header chunk
byte                           Alignment (always 0, ignored)
  32-bit int                   Number of used objects (always 1 in VC Mobile[*])
  (Used object array)          24-byte object name * number of used objects (first object name is empty and therefore unused)
(02 00 01)h + 32-bit offset    GOTO main script space (third header chunk is compiled only in script multifile)
byte                           Alignment (always 0, ignored)
  32-bit int                   Main script size
  32-bit int                   Largest mission script size
  16-bit int                   Number of mission scripts (120 in total)
  16-bit int                   Number of exclusive mission scripts (possibly 1 in III, 2 in VC)
  (Multi script array)         32-bit offset * number of mission scripts
(Main script space)            Space of main script (equal to size defined earlier)
(Mission scripts space)        Space of mission scripts (each one is stored at file offsets defined earlier)

^ Compiler-wise, the model names of level objects are picked directly from OBJS and TOBJ sections of the IDE files whose IDE Filename begins with DATA\ in gta_vc.dat.