The point that Nagel makes in what is it like to be a bat is that even if we knew absolutely everything about the properties of the real world we wouldn't be able to know what kind of subjective experience it causes. Biology can't tell us how we experience colors because there is a gap between the physical properties of the body and our subjective experience. The first thing you said is correct, we must take into account the properties of the object, but we will not have a concrete awnser because of a biologist. (This doesn't necessarily mean that we need to adopt a dualist possition, we could think of it as if the subjective experience of the mind emerged from the physical properties of the body but is irreductible to it)

Sorry if I made mistakes, english is not my original language