re-GTA/README.md

Intro

The aim of this project is to reverse GTA III for PC by replacing parts of the game one by one such that we have a working game at all times.

Apparently you can download a binary of the latest version here.

Re3 starts the script main_freeroam.scm by default. Make sure you copy it to your data directory.

Strategy

A good approach is to start at the fringes of the code base, i.e. classes that don't depend on code that we don't have reversed yet. If a function uses only few unreversed functions that would be inconvenient to reverse at the time, calling the original functions is acceptable.

Progress

This is a list of some things that have been reversed to some non-trivial extent. Not everything is listed, check the code.

CPool
CTxdStore
CVector
CVector2D
CMatrix
CModelInfo
CBaseModelInfo
CSimpleModelInfo
CTimeModelInfo
CClumpModelInfo
CPedModelInfo
CVehicleModelInfo
CVisibilityPlugins
CRenderer
CSprite
CSprite2d
CFont
CEntity
CPhysical
CCollision
CCullZones
CTheZones
CPathFind
CCam
CParticle
CParticleMgr

Low hanging fruit

There are a couple of things that have been reversed for other projects already that could probably be put into this project without too much effort. Again, the list is not complete:

• Animation (https://github.com/aap/iii_anim)
• File Loader (https://github.com/aap/librwgta/tree/master/tools/IIItest)
• ...

Coding style

I started writing in Plan 9 style, but realize that this is not the most popular style, so I'm willing to compromise. Try not to deviate too much so the code will look similar across the whole project.

To give examples, these two styles (or anything in between) are fine:

type
functionname(args)
{
	if(a == b){
		s1;
		s2;
	}
	if(x != y)
		s3;
}

type functionname(args)
{
	if (a == b) {
		s1;
		s2;
	}
	if (x != y)
		s3;
}

This one (or anything more extreme) is heavily discouraged:

type functionname ( args )
{
  if ( a == b )
  {
    s1;
    s2;
  }
  if ( x != y )
  {
    s3;
  }
}

Indentation is done with TABS.

As for the less cosmetic choices, here are some guidelines how the code should look:

• Don't use magic numbers where the original source code would have had an enum or similar. Even if you don't know the exact meaning it's better to call something FOOBAR_TYPE_4 than just 4, since 4 will be used in other places and you can't easily see where else the enum value is used.

• Don't just copy paste code from IDA, make it look nice

• Use the right types. In particular:

  • don't use types like __int16, we have int16 for that

  • don't use unsigned, we have typedefs for that

  • don't use char for anything but actual characters, use int8, uint8 or bool

  • don't even think about using win32 types (BYTE, WORD, &c.) unless you're writing win32 specific code

• As for variable names, the original gta source code was not written in a uniform style, but here are some observations:

  • many variables employ a form of hungarian notation, i.e.:

  • m_ may be used for class member variables (mostly those that are considered private)

  • ms_ for (mostly private) static members

  • f is a float, i or n is an integer, b is a boolean, a is an array

  • do not use dw for DWORD or so, we're not programming win32

• Generally, try to make the code look as if R* could have written it