Add simple tile visibility checking in the ViewModule

yup... hence use of bitwise operators is also recommended. (multiplication by 2 should be replaced with one right shift, and division by 2 should be replaced by one left shift)..

there are many more such optimizations ... 
http://books.google.com/books?id=IRN0IEXJzKEC&pg=PA92&lpg=PA92&dq=floating+point+division+multiplication+optimization+c%2B%2B&source=bl&ots=P1mjHg8EAs&sig=sZD71hukKFcJ6RaBJz4Q5awC9gs&hl=en&sa=X&ei=hZUXVNvRENSn8QGvq4HoBw&ved=0CFEQ6AEwBw#v=onepage&q=floating%20point%20division%20multiplication%20optimization%20c%2B%2B&f=false