My thoughts on the optimization situation is that there has to be a balance between acceptable performance and eye candy that fits within the mission author's time and effort. We don't want to exclude people based on their computer specs, but we can't limit ourselves from making more intricate (high poly /shadow) missions that allow TDM to stay relevant. I know TDM is never going to be cutting edge on graphics but compare some of the really old FMs to todays and the increase in visual fidelity is quite obvious.
Actually, from my experience TDM handles higher fidelity surprisingly well, for engine this old. The thing is, and this is actually true for any engine out there, you need to make a whole map with static meshes. And they have to be optimised for your engine, both in terms triangle count and shaders / materials they use (i.e. they should use as few materials as possible). Some things seem to scale with hardware, like triangle or shadow count or texture memory (although we're probably limited to something like 8192px textures by the engine itself). What doesn't change is the drawcall limit, at least in my experience with different hardware. The easiest way to clog your video pipeline is to make static meshes with high number of materials, which a lot of TDM models do, whether it's modules or decoration props. I understand the reason for that was to use as many versatile tiling textures as possible, to make the mod package easier to download. Also that method was widely used around Thief3 era, where textures were 256 or 512px at best, and making UVs in that texture space was less efficient. The thing is, while games like Thief 3 used 2-3 materials per mesh on average, to save on performance. TDM went wild that count, often using 8 or 10 different materials per mesh (15 was the highest value I've seen in the model browser). That's way too excessive. Add complicated, multi-stage materials, and multiple or overlapping lights (something easy to miss, if you're inexperienced mapper), and you have a recipe for disaster. That is what is both the source of performance problems, but it also presents huge opportunity for future improvement.
To tackle these problems, you have to take the path basically all post-Doom3/Thief3 games took, and switch to "environment sets" (let's forget about lightmaps for a while ). Usually, such set contains modular architecture pieces, versatile background props/decorations, and unique models ("hero meshes"), along with a few tiling textures, if need be. They are as flexible as possible, and the new props or decorations are modelled along the way, or mixed/taken from other asset packs. They are also fully unwrapped and use as few textures/materials as possible.
None of this is easy though. It requires a lot of time, and a knowledgable modeller, something TDM never really had in ample supply (at least that's my impression after a few talks with fellow mappers and TDM team members).
Edited by Judith, 08 February 2018 - 11:25 AM.