1. A drawing apparatus comprising: a dividing unit dividing a rectangle frame circumscribing a triangle displayed on a display screen into a plurality of rectangle segments; a determining unit sequentially performing a determining process of determining whether each rectangle segment included in the rectangle frame overlaps the triangle in a predetermined direction and outputting a determination result of overlap or nonoverlap; a determination control unit ending the determining process in the predetermined direction if the determination result output from the determining unit changes from the overlap to the nonoverlap; and drawing unit performing a drawing process on the rectangle segment determined to overlap the triangle by the determining unit, wherein the determination control unit allows the determining unit to perform an orthogonal direction determining process of determining whether the triangle overlaps a rectangle segment adjacent to the rectangle segment determined to overlap the triangle in a direction orthogonal to the predetermined direction.