Coons Patch
A Coons patch is used to blend surfaces together. For example, you would use a Coons patch at a corner where three fillets (each of a different radius) meet.
Data Format:
le_curve u = 0 boundary
ri_curve u = 1 boundary
dn_curve v = 0 boundary
up_curve v = 1 boundary
point_matrix[2][2] Corner points
uvder_matrix[2][2] Corner mixed derivatives
ri_curve u = 1 boundary
dn_curve v = 0 boundary
up_curve v = 1 boundary
point_matrix[2][2] Corner points
uvder_matrix[2][2] Corner mixed derivatives