Abstract: This method includes: generating data of a mask surface with respect to visualization data arranged in a virtual three-dimensional space, for calculation values at respective calculation points; identifying, from a first data storage storing, as time-series data, positions of the calculation points and calculation values at the calculation points, a first point whose position is closest to a predetermined point on the mask surface; reading out, from the first data storage, a position of the identified first point in each time; arranging the mask surface in each time based on a direction of a user's sight line and the read position in each time so as to make the mask surface perpendicular to the direction of the user's sight line and have the predetermined point on the mask surface arranged at the read position; and drawing polygon data of the visualization data and the mask surface in time series.