Divide two intervals into sub-intervals.

Input parameters:

1. Iu → Primary interval to divide.
2. Iv → Secondary interval to divide.
3. Cu → Number of equal length sub-intervals to be created in the primary direction.
4. Cv → Number of equal length sub-intervals to be created in the secondary direction.

Output parameters:

1. Ui → Grid of sub-intervals in the u direction.
2. Vi → Grid of sub-intervals in the v direction.