The disclosure is directed towards methods and apparatus to detect effective tiling area and fill tiles efficiently. The method improves efficiency by not filling tiles within an inner box in a shape having a large unfilled area. One example method includes detecting an inner box, determining whether the detected inner box is big enough for pre-clipping, and confirming that the outer clip path contains the inner box. When filling tiles into a bounding rectangle tiling area, it is determined if a particular tile (or tile(s)) falls into an inner box or not, and if the tile falls in the inner box, that particular tile is not filled. According to one embodiment, the inner box is an internal rectangle that contains a maximum area in which it is unnecessary to fill tiles.