3D viewer: Parallelized 3D model vertex normal calculations to use all...

3D viewer: Parallelized 3D model vertex normal calculations to use all available CPU cores for significant speedup.

3d-viewer/3d_mesh_model.cpp

@@ -31,6 +31,10 @@
 #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;
@@ -355,13 +359,18 @@ 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() );
+
     // for each face A in mesh
+    #ifdef USE_OPENMP
+    #pragma omp parallel for
+    #endif /* USE_OPENMP */
     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;
-        face_A_normals.clear();
-        face_A_normals.resize(m_CoordIndex[each_face_A_idx].size());
+        std::vector< glm::vec3 >& face_A_normals = m_PerFaceVertexNormals[each_face_A_idx];
+        face_A_normals.resize( m_CoordIndex[each_face_A_idx].size() );
 
         // loop through all 3 vertices
         // for each vert in face A
@@ -402,7 +411,5 @@ void S3D_MESH::calcPerPointNormals ()
             }
 
         }
-
-        m_PerFaceVertexNormals.push_back( face_A_normals );
     }
 }