Question regarding rshares on curation rewards

I don't know where to find the answer to this question but, I would like to know how "rshares" are converted into curation rewards inside the steem blockchain.
I know that there is a Steem Rewards fund and a Vesting fund, but I don't know how, after upvoting a post with a certain amount of "rshares", how the blockchain determines the amount of Steem and SBD to be given as a reward.