I didn't start with much of a strategy beyond getting a previous game template I wrote running with a wad loader and doing the renderer. Later I decided that I wanted to try and rewrite the Doom source for max Doom compatibility.
At first I started to transform previous rendering stuff to Doom structure, this for the most part seems to have worked okay. Next I started to look at how the Thinker objects were done, and this lead me down a very deep rabbit hole...
There are many main areas:
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Object storage
-
Modifying objects
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Base object info and creation
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Game states
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Input
-
Rendering
Things need access to many different areas, like segs, lines, other Things. This means for Rust borrows to be satisfied some parts will need to be spit in to structs, and kept in a parent struct. Like so:
- Game, the full game and state container. Does state management, level loads, orchestration etc
- Map/Level, contains the level data and functions to work with it
- Thinkers, all thinkers, these need access to the Map data
- Functions and associated globals in their files can be encapsulated as Struct+impl
The below is copied from the FILES2 list in the Linux Doom port.
-----------------------------------------------------------------------
Global and misc. stuff
-----------------------------------------------------------------------
doomdata.h - external data definitions (WAD file structure)
doomdef.h - internal data definitions (game structs)
dstrings.h - printed strings for translation, english
d_french.h - printed strings for translation
info.h
info.c - LUT's for Thing TAB, Frame TAB,
generated by multigen utility
dutils.h
dutils.c - Dave's utilities
including doubly-linked lists & simple state machines.
Used in WI, ST, AM, and d_main.c
------------------------------------------------------------------------
DOOM game loop and top level stuff
------------------------------------------------------------------------
g_game.c - Game loop functions, event handling etc.
boolean G_CheckDemoStatus (void);
void G_ReadDemoTiccmd (ticcmd_t *cmd);
void G_WriteDemoTiccmd (ticcmd_t *cmd);
void G_PlayerReborn (int player);
void G_InitNew (skill_t skill, int episode, int map);
void G_DoReborn (int playernum);
void G_DoLoadLevel (void);
void G_DoNewGame (void);
void G_DoLoadGame (void);
void G_DoPlayDemo (void);
void G_DoCompleted (void);
void G_DoVictory (void);
void G_DoWorldDone (void);
void G_DoSaveGame (void);
d_main.c - event handling, D_DoomMain() and other functions
NOT int main()
d_net.c - high level networking protocol code
------------------------------------------------------------------
I Interfaces, system specifics
------------------------------------------------------------------
i_main.c - main(), calls D_DoomMain().
i_svgalib.c - Linux SVGAlib code, including main(),
replaces i_main.c
i_x.c - X11 with SHM code, use with i_main.c
i_dga.c - X11 DGA code, use with i_main.c
i_unix.c - fixed point, networking, and display stuff for UNIX
i_ibm.c - IBM DOS VGA graphics and key/mouse/joystick,
use with i_main.c
i_pcnet.c - IPX networking, DOS
fpfunc.S - fixed point assembly and (currently) duplicate of
tmap.S - texture mapping assembly (currently unused)
------------------------------------------------------------------
AM AutoMap
------------------------------------------------------------------
am_data.h - vector graphics for the automap
am_map.h
am_map.c - automap code
------------------------------------------------------------------
HU Heads Up
------------------------------------------------------------------
hu_lib.h
hu_lib.c - heads-up text and input code
hu_stuff.h
hu_stuff.c - Heads-up displays
-------------------------------------------------------------------
M Menu
-------------------------------------------------------------------
m_menu.c - DOOM options code and leaving messages
m_misc.c - misc. HUD text display, input checks, and
random table, file I/O
-------------------------------------------------------------------
P Play???
-------------------------------------------------------------------
p_local.h - header for all play modules
p_spec.h - specials, lighting, doors, plats, texture animation
p_spec.c - specials, texture animation
p_doors.c - door code
p_plats.c - platform raising/lowering code
p_ceilng.c - active (e.g. crushing) ceilings
p_floor.c - active (e.g. raising) floors
p_lights.c - dynamic (e.g. flickering) lighting
p_switch.c - button switches and animation
p_enemy.c - enemy AI and animation
p_inter.c - object/object interaction?
p_map.c - movement objects, handling of collisions
p_maputl.c - distance, position etc. utilities for movement
p_mobj.c - mobile objects handling, spawn etc.
p_user.c - more movement, bobbing etc.
p_telept.c - teleportation code
p_sight.c - LOS checks, REJECT
p_pspr.c - weapon overlays, bobbing, raising, sprite tables,
firing, ammo bookkeeping
p_setup.c - load map from WAF file, setup code
p_tick.c - savegame function (archive/unarchive),
thinker list handling, allocation,
game tick execution (updates)
-------------------------------------------------------------------
R Rendering
-------------------------------------------------------------------
r_local.h - header for all rendering modules,
internal map data structure definitions
r_bsp.c - BSP seg's clipping
r_data.c - texture column caching, patch assembly,
flats, colormaps, sprites,
lookup by name
r_draw.c - access to framebuffer API, drawing C functions
r_main.c - geometry functions, trigonometry lookups,
R_RenderPlayerView
r_plane.c - floor/ceiling visplanes, sky
r_segs.c - drawing segs, marking hslices for floors/ceilings
r_things.c - sprite and sprite frame/rotation handling, drawing
tables.c - trigonometry lookup tables, static
v_video.c - gamma correction lookup, patch drawing to rectangle
-------------------------------------------------------------------
S Sound
-------------------------------------------------------------------
s_sound.c - more sound and music handling
soundst.h - sound and music data structures
sounds.h
sounds.c - sound and music lump LUT's (manually maintained)
sndserver.h
sndserver.c - (Irix) sndserver code
irix.h
irix.c - SGI Irix sound/sndserver support code
linux.c - Linux voxware sound/sndserver support code,
replaces irix.c, uses irix.h
sun.c - SUN replacement for irix.c
i_sound.h
i_sound.c - DOS DMX music and sound interface
-------------------------------------------------------------------
ST STatus bar
-------------------------------------------------------------------
st_lib.h
st_lib.c - status bar widget code
st_stuff.c
st_stuff.h - status bar code
-------------------------------------------------------------------
W Wad file I/O
-------------------------------------------------------------------
w_wad.c - lump based functions
wadread.h
wadread.c - lump I/O, get SFX
-------------------------------------------------------------------
WI WIn / level end screens
-------------------------------------------------------------------
wi_data.h - lookups for intermission screens, patch positions
wi_stuff.h
wi_stuff.c - intermission animation patchwork
-------------------------------------------------------------------
Z Zone memory allocation
-------------------------------------------------------------------
z_zone.c
-------------------------------------------------------------------
F Final screen animation
-------------------------------------------------------------------
f_finale.c - DOOM mission end screens? (bunny)