List the names of the directors whose films grossed over $100 million.
films grossed over $100 million refer to movie_title where total_gross > 100000000;
SELECT DISTINCT T2.director FROM characters AS T1 INNER JOIN director AS T2 ON T1.movie_title = T2.name INNER JOIN movies_total_gross AS T3 ON T1.movie_title = T3.movie_title WHERE CAST(REPLACE(trim(T3.total_gross, '$'), ',', '') AS REAL) > 100000000