What you're describing is GC-MS, which indeed returns a spectrographic signature that is used to identify a molecule. As noted by @Terr_, that tells you what a

What you're describing is GC-MS, which indeed returns a spectrographic signature that is used to identify a molecule. As noted by @Terr_, that tells you what a molecule is made of but not what shape it is. That being said, the smaller the molecule the easier it is to accurately predict what shape it will be. When computational methods become questionable, you move on to NMR (and a whole host of other techniques). The real issue here is that olfaction involves a small molecule interacting with multiple different proteins for your body to "read" it. We're not so great at the whole predicting drug-protein interaction thing just yet - some closely related fields include virtual screening, molecular dynamics, protein crystallography, X-ray diffraction, and cryoEM (among others).