About No One Lives Forever: I have the full game now (GOTY / 1.004 version) but I haven't been fully testing it with dgVoodoo2 yet. However, I've kept in mind the issue I had with the demo and spotted a good example area with "changing lightmaps" where I suspected heavy performance loss could occur and tested it with dgVoodoo2.
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It's a ventilation shaft with very simple geometry and textures yet the performance loss is severe, probably due to the flickering lightmap since there's not much else going on. There are also no light fixtures with lens flares here so I guess we can put that theory to rest.
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The game runs smoothly on far more complex scenes.
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Also, noticed heavy framerate drop in some of the menus.
Here is a saved file inside the ventilation shaft.