Mesh rendering issue libgdx

I have a very simple program, that loads an wavefront obj file, rotate and displays it. The problem is that the program renders it with some issues (like missing triangles). I had a similar problem when I tried to render a Pyramid with a vertex buffer taken from NeHe's tutorial. So I don't know what cause this rendering issues. Can you help me? ``` package com.jam.libgdx3DTest; import com.badlogic.gdx.Game; import com.badlogic.gdx.Gdx; import com.badlogic.gdx.graphics.*; import com.badlogic.gdx.graphics.g3d.loaders.obj.ObjLoader; import java.io.InputStream; public class Libgdx3DTest extends Game { private Mesh shuttleMesh; private Camera camera; private float rotateAngle; public void create() { if (shuttleMesh == null) { InputStream in = Gdx.files.internal("shuttle.obj").read(); shuttleMesh = ObjLoader.loadObj(in, false); } } public void render() { Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT); Gdx.gl10.glMatrixMode(GL11.GL_MODELVIEW_MATRIX); Gdx.gl10.glLoadIdentity(); camera.update(); camera.apply(Gdx.gl10); rotateAngle += 0.5f; Gdx.gl10.glRotatef(rotateAngle, 0f, 1f, 0f); Gdx.gl10.glRotatef(-90f, 1f, 0f, 0f); shuttleMesh.render(GL11.GL_TRIANGLES); } public void resize(int width, int height) { float aspectRatio = (float) width / (float) height; camera = new PerspectiveCamera(67, 2f * aspectRatio, 2f); camera.translate(0f, 0f, 12f); } public void pause(){ } public void resume(){ } public void dispose() { } } ```