Is there any opencart extension where I can use address generated by my personal bitcoin daemon? I want to integrate pay via bitcoin option on my website but I dont want to use any third party payment gateways like bitpay or BIPS what I want is a extension of opencart in which I can pass username and password of the daemon running on my server and the extension generate new addresses for every customer upon request.

I can do it by changing php files of opencart but that will take time so I am looking for a ready to use extension.
I do not believe an opencart extension exists.

If you set RPC User and RPC Pass in bitcoin.conf you can use Bitcoind's JSON-RPC:

https://en.bitcoin.it/wiki/API_reference_%28JSON-RPC%29

I'll add that doing this opens up a whole slew of security vulnerabilities that would need to be addressed. Having your server communicate with your personal Bitcoin daemon over the public network opens up all kinds of issues and I would strongly discourage it.

Alternatively, you could generate a bunch of addresses using your Bitciond and upload the public keys to a DB or txt file on your server, display each address only once and associate it with an order in opencart.