# Synopsis

PDX_MSGT gdx_EvalSurfaceNormal(long option, MDA_PTR db_ptr, double uval, double vval, double normal[3])

# Purpose

Evaluate a normal on a GDX surface entity

# Description

At U and V parameter values, evaluate a normal on the GDX surface entity.

# Input

## option

### GDX_UNNORM

Unnormalize the parameter values

### GDX_FROMLEFT

Evaluate the point location from the left

### GDX_FROMLOW

Evaluate the point location from the low parameter direction

## db_ptr

The GDX surface entity database pointer

## uval

The U parameter value to evaluate

## vval

The V parameter value to evaluate

# Output

## normal

The XYZ 3D evaluated normal direction vector (normalized)

# Return

          GDX_DEGEN_PARM
          GDX_NOERR
          Low level error return
          .fi