Area light test


天空照明ばかりではさすがに飽きてきた。室内シーンも作ってみたいので、
とりあえずエリアライトを追加してみました。
I added some lines of program to suport the area light souces. One of the result images is above.
By the way, I really want to rewrite my renderer because my source code has been getting like spaghetti.