1. Experiments with implementing a simple raytracer in Doom3

the simple raytracer is approximately 1442 lines of C++ code which now resides inside a fork of the dhewm3 code available on github: https://github.com/gaiusm/pybot-dhewm3.
there are many limitations of the raytracer and some include:
- currently all textures are either inbuilt and override the doom3 equivalent
  - single dark yellow colour used for wood
  - single dark red used for a red tile etc
  - walls are an off white single colour
- any room outline (along the wall for example) is a product of lighting and shadows
any doom3 texture required which is not inbuilt results in a default glass texture
- hence the transparent monsters, which give a Predator feel to the screenshot
finally this is completely done in software and is very slow
- a proof of concept and designed to yield cover art for manuals and posters
on a 4 GHz machine these scenes took about 40 minutes to compute (on a single core)
the screenshot is generated by pressing the console key: ~ and then typing:
```
rt_screenshot 1920 1080
```
the next improvement will be to extend the raytracer to use the Doom3 textures
the map was created using Chisel
and the map source file used by Chisel

chisel/maps/lighting17.txt

define 1 room 1 [defroom] [redfloor]
define 2 room 2 [defroom] [bluefloor]
define 3 room 3 [defroom] [greenfloor]
define 4 room 4 [defroom] [purplefloor]
define 5 room 5 [defroom] [blackfloor]
define 6 room 6 [defroom] [slatefloor]
define 7 room 7 [defroom] [aquafloor]
define 8 room 8 [defroom]
define S worldspawn

define R ammo ammo_rockets_large 16
define G ammo ammo_grenade_small 16
define L ammo moveable_item_rocketlauncher 1
define A ammo item_medkit 1
define l light
define d default ceil colour 210 199 130
define N monster monster_demon_hellknight
define O monster monster_demon_imp
define X monster monster_demon_tick

define yellow colour 190 180 170
define darkyellow colour 190 185 66
define flame colour 170 107 7

define red colour 180 0 0
define blue colour 0 0 180
define green colour 0 180 0

define f light type floor
define m light type mid
define defroom default light mid [yellow] default light ceiling [flame]

define redfloor default texture floor textures/quake1/red_tile_floor
define bluefloor default texture floor textures/quake1/blue_tile_floor
define greenfloor default texture floor textures/quake1/green_tile_floor
define purplefloor default texture floor textures/quake1/purple_tile_floor
define blackfloor default texture floor textures/quake1/black_tile_floor
define slatefloor default texture floor textures/quake1/slate_tile_floor
define aquafloor default texture floor textures/quake1/slate_aqua_floor
define ceiling default texture ceiling textures/quake1/pine_wood


##################################
# 1              # 2             #
#              N #               #
#                #               #
#                .               #
#                .               #
# S              #               #
#                #               #
###..#########################..##
# 3    #  4   # 5   #  6  #     #
#      .      .     .     .  7  #
#      .      .     .     .     #
#      #      #     #     #     #
############################==###
                          #     #
                          #  8  #
                          #  R  #
                          # G L #
                          #  A  #
                          #######

the textures were taken from the doom3 hidef replacement pack and also the quake1 ten year revitalisation project
firstly here are some in game screenshots (no raytracing)
the following two screenshots are taken after new high resolution textures have been added from: https://ambientcg.com
the wall texture has now been upgraded to a 4k texture and new wood textures also from https://ambientcg.com have been added. Attempting a Quake 1 feel in the Dhewm3 engine
the in game screenshots set a high yardstick which the ray tracer must beat
- as can be seen the requirement to introduce Doom3 textures into the raytracer is paramount.
and here are the results after implementing a simple ray tracer in Doom3