How to know the value at the center of trilinear hexahedral element

[Stacky]

Hello,
If we know the value of the field variables at the nodes of hexahedral element. How one finds the value at the center of the element. The hexahedral element is trilinear and solved using 2x2x2 gauss quadrature rule.

 

[AlephZero]

Use the element shape functions.

The answer should be the average of the 8 nodal values.