The main goal of this 1.3.0 release is enabling modders the ability to make new content using up to date Material & Lighting standards. Adding PBR is a requirement to make the new content look the same in RBDOOM-3-BFG as in Blender 2.9x with Cycles or Eevee and Substance Designer. PBR became the standard material authoring since 2014. Many texture packs for Doom 3 like the Wulfen & Monoxead packs were made before and are heavily outdated. With this release modders can work with modern tools and expect that their content looks as expected.
However the PBR implementation is restricted to standard PBR using the Roughness/Metallic workflow for now.
Specialized rendering paths for skin, clothes and vegetation will be in future releases.
Implementing Physically Based Rendering (PBR) in Doom 3 is a challenge and comes with a few compromises because the Doom 3 content was designed to work with the hardware constraints in 2004 and that even meant to run on a Geforce 3.
The light rigs aren't made for PBR but it is possible to achieve good PBR lighting even with the old content by tweaking the light formulars with a few good magic constants. However I also want to support the modding scene to allow them to create brand new PBR materials made with Substance Designer/Painter or other modern tools so multiple rendering paths have been implemented.
PBR allows artists to create textures that are based on real world measured color values and they look more or less the same in any renderer that follows the PBR guidelines and formulars.
RBDOOM-3-BFG 1.3.0 brings back the Quake 3 light grid but this time the grid points feature spherical harmonics encoded as octahedrons and it can be evaluated per pixel. This means it can be used on any geometry and serves as an irradiance volume.
Lightgrids can be baked after loading the map and by typing:
```
bakeLightGrids [limit]
```
This will generate a ***.lightgrid*** file next to your .map file and it will also store a light grid atlas for each BSP area under ***env/maps/<path/to/your/map/>***
Limit is 4096 by default and means the maximum number of light grid points in a single light grid.
Quake 3 had one light grid that streched over the entire map and distributed lighting every 64 x 64 x 128 units by default.
If the maps were too big then q3map2 made the default grid size broader like 80 x 80 x 144, 96 x 96 x 160 and so on until the maximum number of light grid points was reached.
The Quake 3 approach wouldn't work with Doom 3 because the maps are too big and it would result in up to 800k probes for some maps or the grid density would very coarse.
RBDOOM-3-BFG uses the bounding size of the BSP portal areas and puts and smaller light grid into those BSP areas.
This way we can maintain a good grid density and avoid wasting storage because of light grid points that are in empty space.
> But what is an Irradiance Volume or Light Grid exactly?
It tells each model or lit pixel how the indirect diffuse lighting is coming from any direction. The Probulator page by Yuri O'Donnell has some good examples:
Left: The captured view using a panorama layout. Right: The Diffuse lighting using Level 4 Spherical Harmonics aka Irradiance.
Now think of this for each of the grid points in RBDOOM-3-BFG. If a model is placed between those probes the lighting will be interpolated by the nearest 8 grid points similar like in Quake 3.
Quake 3 only stored the dominant light direction, the average light color of that direction and an ambient color term for each grid point.
In RBDOOM-3-BFG you basically can have the diffuse lighting information for **any** world space direction instead.
This is a way more advanced technique.
### Image Based Lighting and Environment Probes
Environment probes supplement the light grids. While light grids provide diffuse lighting information the signal isn't good enough to provide specular lighting. This is where environment probes are needed. There are less of them
If an level designer doesn't put any env_probe entities into a map then they are automatically distributed through the map using the BSP area bounds and placed in the center of them.
Environment probes can be computed after loading the map and by typing:
```
bakeEnvironmentProbes
```
This will generate EXR files in ***env/maps/<path/to/your/map/>***.
The environment probes use an octahedron encoding and the specular mipmaps are convolved using the Split Sum Approximation by Brian Karris [Epic 2013]. Convolving the environment probes is done on the CPU using the id Tech 5 multi threading code so it will consume all your available cores.
For artists this basically means if you increase the roughness in your material then you increase the mip map level of the environment probe it samples light from and it gets blurier.
If you haven't downloaded the additional baked light data from the [RBDOOM-3-BFG ModDB Page](https://www.moddb.com/mods/rbdoom-3-bfg) and just run RBDOOM-3-BFG.exe with the required DLLs (or you built it yourself) it will use an internal fallback.
RBDOOM-3-BFG.exe has one prebaked environment probe that is compiled into the executable.
It's the light data from the Mars City 1 lobby in the screenshot above. Using this data for the entire game is inacurrate but a better compromise than using a fixed global light direction and some sort of Rim lighting hack like in version 1.2.0.
The default irradiance / radiance data gives the entire game a warmer look and it fits for being on Mars all the time.
Left: No extra ambient pass. Ambient is pure black like in original Doom 3. Right: Extra ambient pass with r_forceAmbient 0.5 using local environment probe for irradiance and radiance lighting.
It's usually rendered with Blinn-Phong specular with a fixed specular exponent.
Specularmaps are more or less Gloss maps.
In RBDOOM-3-BFG it uses the PBR GGX Cook-Torrence formular and you can vary the roughness along the material like in other modern engines and you usually define a texture with the _rmao suffix.
The engine will also look for _rmao.[png/tga] overrides for old materials and if it finds those it will render them using a better PBR path. Old school specularmaps also go through a GGX pipeline but the roughness is estimated from the glossmap.
The Ambient Occlusion will be mixed with the Screen Space Ambient Occlusion and will only affect indirect lighting contributed by the environment probes.
## Filmic Post Processing
TL;DR If you enable it then you play DOOM 3 BFG with the optics of a Zack Snyder movie.
This release adds chromatic abberation and filmic dithering using Blue Noise.
The effect is heavy and is usually aimed in Film production to mix real camera footage with CG generated content.
Dithering demonstration: left side is quantized to 3 bits for each color channel. Right side is also only 3 bits but dithered with chromatic Blue Noise. The interesting fact about the dithering here is shown in the upper debug bands.
The first top band is the original signal. The second shows just 8 blocks and if you dither the those blocks with Blue Noise then it is close to the original signal which is surprising.
***This is still very much Work in Progress and not supported by the official TrenchBroom.***
Mapping for Doom 3 using TrenchBroom requires an extended unofficial build that is bundled with the official RBDOOM-3-BFG 7z package.
You can find the customized version under tools/trenchbroom/.
Doom 3 also requires some extensions in order to work with TrenchBroom. I usually develop these things for RBDOOM-3-BFG but I created a seperated brach for vanilla Doom 3 so everybody can adopt TrenchBroom and the new Doom 3 (Valve) .map support.
The goal of the TrenchBroom support is to make it easier to create new maps. It doesn't allow to create bezier patches at the moment so you won't be able to edit existing Doom 3 maps.
You can only save maps to the Doom 3 Valve format but you can copy paste from the vanilla Doom 3 .map format into the Doom 3 (Valve)configuration and reset your texture alignment as you want.
TrenchBroom doesn't support brush primitives like in D3Radiant or DarkRadiant and if you are familiar with TrenchBroom then you know that the preferred .map format is some kind of (Valve) .map format for your game.
The Quake 1/2/3 communities already adopted the Valve .map format in the BSP compilers and I did the same with dmap in RBDOOM-3-BFG.
Here is an overview of the changes made to TrenchBroom:
* Doom 3 .map parser with brushDef3, patchDef2, patchDef3 primitives
* Doom 3 Valve .map configuration
* Quake 3 .shader parser adopted to support .mtr
* .mtr support includes support for Doom 3 diffuse stages and the lookup for them is like in idMaterial::GetEditorImage()
* New Doom 3 OBJ parser. My TB Interop branch automatically creates OBJ files to work with TB and it also allows seamless interop with Blender 2.8x and 2.9x with the need of additional model formats for func_static entities (like misc_model for Quake 3)
* D3Radiant usually does not allow to use just textures. Only valid materials work and only materials should be shown in the texture collection overview. However this branch still displays all found textures.
* It has no support for BFG .resource files and .bimage files. BFG only shipped for precompressed textures and no .tga files so people who want to mod for BFG have to copy the vanilla D3 base/textures/* and base/models/* to D3BFG/base/
* Many entities work differently in Doom 3 if they have an origin. Brush work in D3 is usually stored in entity space and not world space. This is a major issue and not solved. I couldn't figure out how to parse the origin first and then translate the brushes accordingly.
* Doom 3's primary model formats are LWO and ASE. LWO and .md5mesh model support is missing.
* Some ASE models can't be loaded and materials are usually all wrong if loaded
### Some Scenes of Mars City 1 loaded into TrenchBroom
* Changed light interaction shaders to use PBR GGX Cook-Torrance specular contribution. The material roughness is estimated by the old school Doom 3 glossmap if no PBR texture is provided
* Improved r_hdrDebug which shows F-stops like in Filament
* Turned off r_hdrAutomaticExposure by default because it caused too much flickering and needs further work. The new default values work well with all Doom 3 content
* SSAO only affects the ambient pass and not the direct lighting and the ambient occlusion affects the specular indirect contribution depending on the roughness of a material. See moving Frostbite to PBR (Lagarde2014)
* Added HACK to look for PBR reflection maps with the suffix _rmao if a specular map was specified and ends with _s.tga. This allows to override the materials with PBR textures without touching the material .mtr files.
* idMapFile and dmap were changed to support the Valve 220 .map format to aid mapping with TrenchBroom
* Added exportFGD [models] console command which exports all def/*.def entityDef declarations to base/exported/_tb/ as Forge Game Data files. TrenchBroom has native support to read those files https://developer.valvesoftware.com/wiki/FGD.
Using the models argument will also export all needed models by entity declarations to base/_tb/ as Wavefront OBJ files.
* To make it easier getting static models from Blender/Maya/3D Studio Max into TrenchBroom and the engine Wavefront OBJ model support has been ported from IcedTech
* Improved Screen Space Ambient Occlusion performance by enhancing the quality with Blue Noise and skipping the expensive extra bilateral filtering pass
* Updated idRenderLog to support RenderDoc and Nvidia's Nsight and only issue OpenGL or Vulkan debug commands if the debug extensions are detected. Reference: https://devblogs.nvidia.com/best-practices-gpu-performance-events/
