does renderer.shadowMap.autoUpdate == false give you ~approximately the same performance as mesh.material.lightmap? I want to use shadows in my static scene, but i dont how much more resources does shadowMap require compared to lightMap, is there a big difference between updating shadowMap once and using lightMap instead shadowMap? People in the internet say that shadowMap is used only for scenes with dynamic shadows
No, it isn’t. Even if you don’t update the shadow maps, their processing in the fragment shader is more expensive compared to light maps (you end up with way more texture fetches and more computations).