1. A computer-readable, non-transitory storage medium storing a program for causing a computer to execute a procedure, the procedure comprising: identifying an axis that is a straight or curved line inside of a space; first generating plural surface regions that are orthogonal to the identified axis; second generating, from a first vector provided at each vertex of an unstructured grid disposed inside of the space, a second vector at each point of plural points on a surface region for each of the generated plural surface regions; and displaying an arrow corresponding to the generated second vector.