|  | B | - pointer to data of size c * n * sizeof(datatype), where c is the number of components in the field.
If B is not NULL, the values of the field are written in this array, varying first by component,
then by point. | 
|  | D | - pointer to data of size d * c * n * sizeof(datatype).
If D is not NULL, the values of the field's spatial derivatives are written in this array,
varying first by the partial derivative component, then by field component, then by point. | 
|  | H | - pointer to data of size d * d * c * n * sizeof(datatype).
If H is not NULL, the values of the field's second spatial derivatives are written in this array,
varying first by the second partial derivative component, then by field component, then by point. |