# udfGetEbcNormDir()

Return the outward normal direction of the surface at the surface quadrature point.

## Syntax

normDir = udfGetEbcNormDir( udfHd ) ;

## Type

AcuSolve User-Defined Example Boundary Condition

## Parameters

udfHd
The opaque handle (pointer) which was passed to the user function.

## Return Value

normDir (Real*)
Pointer to two dimensional real array of the outward normal direction of the surface at the surface quadrature point. The first (fastest) dimension of the array is the number of surfaces, nItems, and the second (slower) dimension is three, for the x, y and z directions.

## Description

This routine returns the outward normal direction of the surface at the surface quadrature point. For example,
Real* normDir ;
Real x_dir, y_dir, z_dir ;
Integer surf ;
...
normDir = udfGetEbcNormDir( udfHd ) ;
for ( surf = 0 ; surf < nItems ; surf++ ) {
x_dir = normDir[0*nItems+surf] ;
y_dir = normDir[1*nItems+surf] ;
z_dir = normDir[2*nItems+surf] ;
...
}

## Errors

• This routine expects a valid udfHd.
• This routine may only be called within an Element Boundary Condition user function.