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Surface Partial Derivative with Respect to the U Parameter Example

This example demonstrates the use of the SDDUF function to calculate the surface partial derivative at half way across SURF1 in the U parameter direction and three-quarters of the way across the surface in the V direction. The partial derivative is calculated with respect to the U parameter of the surface.

   ENTITY/P(8),SPL(4),SURF1
   NUMBER/A(3)
   P(1)=POINT/0,0,0
   P(2)=POINT/1,0,.5
   P(3)=POINT/2,0,0
   P(4)=POINT/2,1,.75
   P(5)=POINT/2,2,0
   P(6)=POINT/1,2,.5
   P(7)=POINT/0,2,0
   P(8)=POINT/0,1,.75
   SPL(1)=SPLINE/P(1..3)
   SPL(2)=SPLINE/P(3..5)
   SPL(3)=SPLINE/P(5..7)
   SPL(4)=SPLINE/P(7),P(8),P(1)
   SURF1=SSURF/PRIMA,SPL(1),SPL(3),CROSS,SPL(2),SPL(4)
   A=SDDUF(SURF1,.5,.75)