Options pricing is also affected by vega and theta. (gamma small factor) Vega is nothing but demand.
Its really silly but some strikes the vega goes up while others not so much. At the same time when all folks jump on shorting the highest OI build up. The vega there goes down much lower compared to other strikes. So if you are wondering why my strike grew only 5% but the strike below and above has grown 6 and 7%. That also happens
(For perfectionists before jumping on me for stating it wrongly as its IVS not vega I am talking on premiums whatever you call them. Whatever I wish to convey its more complex to fine tune and predict the crowd behaviour on options. I am getting the feeling slowly its easier to predict directions on future.)
Nifty vega graph can more or less be viewd on VIX. Though it takes into account all strikes current/next expiry too and not into account our strikes.
Vix generally goes up when nifty falls vice versa. Though the opposit also happens
Seen vix rising when nifty made smart upmoves.
The greatest bonus is sometimes you get money though index stays where it is. Straddle the nifty. Nifty stays where it is. After 2 hours you find profit on both calls and puts. This happens when vix goes up. People just bought up too much of them after you purchased it.