diff --git a/3d-viewer/3d_mesh_model.cpp b/3d-viewer/3d_mesh_model.cpp
index b3ad2924bf..1beaf4c199 100644
--- a/3d-viewer/3d_mesh_model.cpp
+++ b/3d-viewer/3d_mesh_model.cpp
@@ -24,13 +24,17 @@
 
 /**
  * @file 3d_mesh_model.cpp
- * @brief 
+ * @brief
  */
 
 
 #include <3d_mesh_model.h>
 #include <boost/geometry/algorithms/area.hpp>
 
+#ifdef USE_OPENMP
+#include <omp.h>
+#endif /* USE_OPENMP */
+
 S3D_MESH::S3D_MESH()
 {
     isPerFaceNormalsComputed = false;
@@ -118,21 +122,21 @@ void S3D_MESH::openGL_Render()
     for( unsigned int idx = 0; idx < m_CoordIndex.size(); idx++ )
     {
         if( m_MaterialIndex.size() > 1 )
-        {       
+        {
             if( m_Materials )
             {
                 m_Materials->SetOpenGLMaterial( m_MaterialIndex[idx] );
             }
-        }          
-        
-        
+        }
+
+
         switch( m_CoordIndex[idx].size() )
         {
             case 3:     glBegin( GL_TRIANGLES );break;
             case 4:     glBegin( GL_QUADS );    break;
             default:    glBegin( GL_POLYGON );  break;
         }
-        
+
 
         if( m_PerVertexNormalsNormalized.size() > 0 )
         {
@@ -167,7 +171,7 @@ void S3D_MESH::openGL_Render()
                 glNormal3fv( &normal.x );
 
                 glm::vec3 point = m_Point[m_CoordIndex[idx][ii]];
-                glVertex3fv( &point.x );                        
+                glVertex3fv( &point.x );
             }
         }
 
@@ -258,7 +262,7 @@ void S3D_MESH::calcPerFaceNormals ()
 
     //DBG( printf("m_CoordIndex.size %u\n", m_CoordIndex.size()) );
     //DBG( printf("m_PointNormalized.size %u\n", m_PointNormalized.size()) );
-    
+
     for( unsigned int idx = 0; idx < m_CoordIndex.size(); idx++ )
     {
 
@@ -307,7 +311,7 @@ void S3D_MESH::calcPerFaceNormals ()
         if( haveAlreadyNormals_from_model_file == false )
         {
 
-            // normalize vertex normal           
+            // normalize vertex normal
             float l = glm::length( cross_prod );
 
             if( l > FLT_EPSILON ) // avoid division by zero
@@ -331,7 +335,7 @@ void S3D_MESH::calcPerFaceNormals ()
 
             m_PerFaceNormalsNormalized.push_back( cross_prod );
         }
-        
+
     }
 
 }
@@ -354,17 +358,19 @@ void S3D_MESH::calcPerPointNormals ()
     }
 
     m_PerFaceVertexNormals.clear();
-    
+
     // Pre-allocate space for the entire vector of vertex normals so we can do parallel writes
-    m_PerFaceVertexNormals.resize(m_CoordIndex.size());
+    m_PerFaceVertexNormals.resize( m_CoordIndex.size() );
 
     // for each face A in mesh
+    #ifdef USE_OPENMP
     #pragma omp parallel for
+    #endif
     for( unsigned int each_face_A_idx = 0; each_face_A_idx < m_CoordIndex.size(); each_face_A_idx++ )
     {
         // n = face A facet normal
         std::vector< glm::vec3 >& face_A_normals = m_PerFaceVertexNormals[each_face_A_idx];
-        face_A_normals.resize(m_CoordIndex[each_face_A_idx].size());
+        face_A_normals.resize( m_CoordIndex[each_face_A_idx].size() );
 
         // loop through all 3 vertices
         // for each vert in face A
@@ -396,14 +402,14 @@ void S3D_MESH::calcPerPointNormals ()
                 }
             }
 
-            // normalize vertex normal           
+            // normalize vertex normal
             float l = glm::length( face_A_normals[each_vert_A_idx] );
 
             if( l > FLT_EPSILON ) // avoid division by zero
             {
                 face_A_normals[each_vert_A_idx] /= l;
             }
-            
+
         }
     }
 }