It's because of mipmaps.
You are copying only to the main texture, which will not be displayed unless you are very close to the texture. Otherwise, mipmaps will be displayed which haven't been copied to.
Use ClearTextureFilters after Graphics3D (to disable mipmapping) and it will work.
You are copying only to the main texture, which will not be displayed unless you are very close to the texture. Otherwise, mipmaps will be displayed which haven't been copied to.
Use ClearTextureFilters after Graphics3D (to disable mipmapping) and it will work.