Added array functions, scale calculation function

src/utility.cpp

@@ -34,4 +34,36 @@ std::array<double, 3> extract_triplet(const std::string& str_in, size_t& start)
 
 unsigned ij2index(unsigned i, unsigned j, unsigned Ny) {
 	return i * Ny + j;
-}
\ No newline at end of file
+}
+
+
+std::array<float, 3> operator+=(std::array<float, 3>& lhs, const std::array<float, 3>& rhs){
+  lhs[0] += rhs[0];
+  lhs[1] += rhs[1];
+  lhs[2] += rhs[2];
+
+  return lhs;
+}
+
+std::array<float, 3> cross(const std::array<float, 3>& v, const std::array<float, 3>& w){
+  std::array<float, 3> cp;
+  cp[0] = v[1]*w[2] - v[2]*w[1];
+  cp[1] = v[2]*w[0] - v[0]*w[2];
+  cp[2] = v[0]*w[1] - v[1]*w[0];
+
+  return cp;
+}
+
+std::array<float, 3> operator/=(std::array<float, 3>& v, const float d){
+  v[0] /= d;
+  v[1] /= d;
+  v[2] /= d;
+
+  return v;
+}
+
+glm::mat4 scale_z(float z0, float factor){
+  glm::mat4 transf (1.f);
+  glm::mat4 transf = glm::translate(glm::scale(glm::translate(transf, glm::vec3(0.f,0.f,-z0)), glm::vec3(1.,1.,factor)), glm::vec3(0.,0.,z0));
+  return transf;
+}