12. The computer readable storage medium as claimed in claim 11, which further comprises: deletion means for causing the computer to delete, out of the candidate surfaces and the candidate edge lines generated by said second generation means, at least one of a candidate surface and a candidate edge line which cannot possibly exist in a solid.
11. A computer readable storage medium storing a program to be executed by a computer, comprising: extraction means for causing the computer to extract information related to surfaces from the plan views; first generation means for causing the computer to generate candidate surfaces based on the information extracted by said extraction means; second generation means for causing the computer to generate candidate surfaces and candidate edge lines by obtaining intersecting lines among the candidate surfaces generated by said first generation means after the computer is caused to generate the candidate surfaces by said first generation means; third generation means for causing the computer to generate candidate solids by determining combinations of the candidate surfaces generated by said second generation means after the computer is caused to generate the candidate surfaces by said second generation means; and selection means for causing the computer to collate the candidate solids generated by said third generation means with the plan views and to select a matching candidate solid as a solid model after the computer is caused to generate the candidate solids by said third generation means.