Building terrain would fail if pyramid type is selected as Z Tolerance, but it will build successfully when selecting it as window size even though feature class contains null field values.
ArcGIS 10 will return warning if null z encountered but will allow it
対処法
For now, must supply z for all features. Check that none are null before creating terrain. ArcGIS 10 will be more accomodating and will return a warning if a null is encountered but will allow it.