This should be a rough guideline for choosing the correct dimensions and format for your custom TDM texture.
2.08 update (2020)
The guidance is for standard tiling textures. A single large texture with a unique pattern shouldn't cause too much harm, especially if it is
used sparingly. The other consideration is whether this "beautiful" texture matches the pixel density of other textures at natural scale.
You may be admiring your great new texture but players will be looking at TDM textures next to it and thinking "why is everything except the wall
so blurry"? To which the answer will not be "OK, we are going to increase all the texture resolutions and make the game unplayable except for
high-end hardware from 2016+". Doom 3 \ TDM is more texture heavy than many other engines since it relies on normal maps for most detail
so you have to budget textures differently than an engine where half of the detail is baked into the diffuse because of baked lighting. The limit
is there to act as a sane guideline.
- Diffusemap: max. 1024 pixels (when used for smaller areas: 512)
- Normalmap: max. 1024 pixels
- Specular: max. 512 pixels
- Editor image: max. 256 pixels
- Diffusemaps: DDS (DXT1/DXT3)
- Normalmap: TGA (uncompressed, no RLE)
- Specularmap: DDS
- Editor Image: JPG (medium quality (e.g. 85 in Photoshop), not over-compressed)
- If the texture is to be included in TDM : A high res copy of the diffusemap (can be RLE)
Assuming your texture is named rough_grey_dirty, the names are
- Diffusemap: rough_grey_dirty.dds
- Normalmap: rough_grey_dirty_local.tga
- Specularmap: rough_grey_dirty_s.dds
- Editor Image: rough_grey_dirty_ed.jpg
- Nontiling textures have the _nontiling_ part in their name: rough_grey_dirty_nontiling_local.tga
- Textures tiling into one dimension only get the _tiling1d_ part added: rough_grey_dirty_tiling1d_local.tga
- Heightmaps: rough_grey_dirty_h.tga
- Alphamaps: rough_grey_dirty_a.tga
- Occlusion maps: rough_grey_dirty_occ.tga
- Skyboxes: Doom can't handle DDS for Skyboxes, so uncompressed TGA should be used here. If the dimensions of your skybox textures exceed 1024 Pixels, JPEG compression on maximum quality should be applied. (Uncompressed TGA on six 2048 x 2048 textures would result in 72 MB altogether, which is definitely too much and the high resolution will compensate the anyway negligible JPEG artifacts.)
Material File Conventions
See here: Material File Naming Convention
Remember: Do keep a backup of the ultra hi-res versions of your work as well as your working files (photoshop, gimp files). These should be added to the texture_src repository, which keeps all the "working" or "source files".