I exported a scene I made lightmaps for (with Maya) as gltf. The scene with it’s lightmaps imports just fine into 3js. However when I try to reassign a gltf bench model in the same scene a new material that carries the very same lightmap texture it was imported with, it looks way off as if the uvs have changed somehow. You can check it out here https://main--serene-beijinho-9a5d3a.netlify.app/ (use directional keys). I expect no difference when I assign a material carrying the same texture. I am doing this because ultimately after I figure out the problem I intend to multiply the albedo texture into lightmap using the THREE.ShaderMaterial() . I know shaders inherently carry a lightmap property but when I tried it, I found the shadows to be a bit weakish.
Materials and textures have a lot of properties, and if you’re replacing either, all of them need to match the original or things will differ. The most common cause here might be texture.flipY = false. If it isn’t that, you may need to do a deeper comparison of the material and texture properties before/after.
Dynamite! It Works!