I am trying to write a obj file with vertices. I am computing the vertex normals in my code and writing to this file as well. When I try to render this file in Meshlab it reads the vertices correctly, but when I go to 'Render->Show vertex normals', it is not showing the normals that I computed. Rather MeshLab computes its own normals and shows them. I am not sure how I can visualize the normals that I computed/wrote to file. I want to apply Meshlab shader later based on my computed normals. To test this I created a test obj file- vn 0.517350 0.517350 0.517350 v 0.500000 0.500000 0.500000 vn -0.333333 0.666667 0.666667 v -0.500000 0.500000 0.500000 vn 0.666667 -0.333333 0.666667 v 0.500000 -0.500000 0.500000 vn -0.666667 -0.666667 0.333333 v -0.500000 -0.500000 0.500000 f 1//1 2//2 3//3 f 4//4 3//3 2//2 This is just one square. Now if I change the normal values in this file, it still shows its own vertex normals when I select 'Render->Show vertex normals'. How can I have my own normals and apply shader that works on my computed normals?? Please help. Thanks!!