We compile, as if in the yard 1992

I studied the vanilla source code of the 1992 Wolfenstein 3D game. Despite the fact that she is already 25 years old, and she is completely outdated for modern platforms, you can still compile it if you recreate the environment.

This requires only:
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• Wolfenstein 3D source code.
• Dosbox
• Compiler Borland C ++ 3.1.
• Wolfenstein 3D shareware (to borrow resources).

File system setup

Open the command line and create two folders, one for each of the required DOS disks:

cd ~ mkdir system cd system mkdir c mkdir a cd ~ 

Download files

• Download Borland 3.1 in system/a .
• Download the source code Wolfenstein 3D in the system/c
• We download VGA files to system/c (at the end of the article I will explain why this is necessary).

  cd system/a curl -O http://fabiensanglard.net/Compile_Like_Its_1992/tools/BCPP31.zip cd ../c curl -O http://fabiensanglard.net/Compile_Like_Its_1992/tools/wolfsrc.zip curl -O http://fabiensanglard.net/Compile_Like_Its_1992/tools/vgafiles.zip 

Now all files are in the file system. Just to check, we enter:

  cd .. find ~/system 

You should have the following:

  /Users/fabiensanglard/system /Users/fabiensanglard/system/a /Users/fabiensanglard/system/a/BCPP31.zip /Users/fabiensanglard/system/c /Users/fabiensanglard/system/c/vgafiles.zip /Users/fabiensanglard/system/c/wolfsrc.zip 

Unpack everything

  cd ~/system/a unzip BCPP31.zip cd ~/system/c unzip vgafiles.zip unzip wolfsrc.zip 

Dosbox

Download and run DosBox :

We mount

Mount the file system, one folder for each of the disks:

  Z:/> mount c ~/system/c Z:/> mount a ~/system/a 

Install the compiler

It is time to install Borland C ++ 3.1:

  Z:\> a: A:\> cd BCPP31 A:\> install 

Press "enter" when selecting the source disk (drive A must be selected)



Leave all the default settings and select “Start Installation”:



Notifications warn you that you can’t find the Microsoft Windows folder, but we don’t need it, just hit enter.

Installing Wolfenstein 3D Source Code

The system works and has a compiler: it is time to unpack (again) the source code.

  A:\> c: C:\> cd\ C:\> install 

Let's enter "C"



Leave the default path: \WOLFSRC



Confirm ("Y") the creation of the directory.

Fits!

Compile

Launch Borland C ++ 3.1:

  C:\> cd\ C:\> cd borlandc C:\> cd bin C:\> bc.exe 

After clicking on OK, use the mouse or hotkeys to select Project → Open Project ..\..\WOLFSRC\WOLF3D.PRJ :



Select Options → Directories and change the value as follows:

  Include Directories: C:\BORLANDC\INCLUDE Library Directories: C:\BORLANDC\LIB Ouptput Directories: OBJ Source Directories: C:\WOLFSRC 

Let's try to compile: Compile -> Build All



We get the error: “Cannot find executable TASM”



Let's exit Borland C ++, we need to configure PATH:

  C:\> CD .. C:\> PATH=C:\BORLANDC\BIN C:\> BC.EXE 

Try compiling again (Compile -> Build All):



Compilation was done, but a layout error occurred: “Unable to find OBJ file”, because the path to SIGNON.OBJ and GAMEPAL.OBJ in the project is incorrect.

They are noted in C:\SOURCE\WOLF\ :



Remove them from the project (Select Projext → Delete item). Add them again via PROJECT → Add Item .... Add WOLFSRC\OBJ\SIGNON.OBJ and WOLFSRC\OBJ\GAMEPAL.OBJ



Let's try to compile again (Compile → Build All)



It worked! But will the game start?

We get resources

Download the shareware version, or even better: buy Wolfenstein 3D as a full version.

  cd ~/system/c curl -O http://fabiensanglard.net/Compile_Like_Its_1992/tools/1wolf14.zip unzip 1wolf14.zip 

Let's go back to DosBox and install the game in C:\WOLF3D .

  C:\> c: C:\> cd \ C:\> cd 1wolf14 C:\1WOLF14> install 

After installing the game, copy the newly compiled .EXE file into the game folder,

  C:\> c: C:\> cd wolf3d C:\WOLF3D> copy WOLF3D.EXE WOLF3D.OLD C:\WOLF3D> copy ../WOLRSRC/WOLF.EXE 

Run the game

Let's try to run:

  C:\> cd wolf3d C:\WOLF3D> copy WOLF3D.EXE WOLF3D.OLD C:\WOLF3D> copy ../WOLRSRC/OBJ/WOLF3D.EXE . C:\WOLF3D> WOLF3D.EXE 

Hmm, it looks weird ...



Oh…



What?



I do not remember that the game was so ...



So, somewhere an error occurred!

What happened?

The point is in the production pipeline of the game and how it was used by the engine. When Adrian Carmack and Kevin Cloud finished working on all the graphic files, they used the IGRABed tool to package them. The result was 3 + 2 files.

• VGAHEAD.WL1
• VGAGRAPH.WL1
• VGADICT.WL1

The VGAHEAD file is an index containing pointers to VGAGRAPH, which stores data compressed by the Huffman algorithm. VGADICT contains Huffman dictionaries for unpacking data.

Two other files created:

• GRE.H
• GRE.EQU

compiled into the engine, as shown in the figure below:



What are the .H and .EQU files .EQU ? In short, they allow you to access by name. When IGRABed collects all the files, it also creates an enumeration (enum) with the corresponding indexes:

GRE.H

  enum{ H_WOLFLOGOPIC GETPSYCHEDPIC L_GUYPIC . . } graphicnums 

GRE.EQU

  H_WOLFLOGOPIC = 0 GETPSYCHEDPIC = 1 L_GUYPIC = 2 

Thus, when the engine requests the desired resource, it can use a logical name (L_GUYPIC), rather than a “magic number” (2).

This means that the engine was released with hard-coded image indices in VGA files. Since the resources and the code base evolved after the release of wolf3D shareware (in Spear of Destiny), the new compiled game indexes do not match the location of the source resource files.

Start the game (again)

Fortunately, this problem has a simple solution: someone re-generated VGA resources to match the indexes in the .H and .EQU files released with the source code. Simply copy these files (if you use resources from the shareware version, you will need to change the file extension from .WL6 to .WL1).

  C:\> copy C:\vgafiles\VGADICT.WL6 C:\WOLF3D\VGADICT.WL1 C:\> copy C:\vgafiles\VGAGRAPH.WL6 C:\WOLF3D\VGAGRAPH.WL1 C:\> copy C:\vgafiles\VGAHEAD.WL6 C:\WOLF3D\VGAHEAD.WL1 

Let's try again:

  C:\WOLF3D> WOLF3D.EXE 

Works!



But we still haven't finished!

VGA frame buffer and screen aspect ratio

This may not be obvious to people who have never seen the original game, but the above picture from DosBox does not exactly coincide with what the players saw in 1992. The VGA frame buffer had a size of 320x200, but for a CRT monitor the aspect ratio is 4: 3. This means that the frame buffer when stretched to the monitor vertically stretched. DosBox has an option to compensate for this:

  vi ~/Library/Preferences/DOSBox\ 0.74\ Preferences [render] # frameskip:  ,  DOSBox   . # aspect:    .      ,       ! # scaler:   /   . #    'forced',  scaler ,      . #  : none, normal2x, normal3x, advmame2x, advmame3x, advinterp2x, advinterp3x, ... frameskip=0 aspect=false scaler=normal2x 

Change the aspect value to true .

Let's try again:

  C:\WOLF3D> WOLF3D.EXE 

Finally it worked!