当我使用视锥体方法时，没有显示任何内容？

Question

我正在画一个茶壶，但画布上没有显示任何内容，当我使用glOrtho（）方法时，茶壶显示没有问题。我想使用gluLookAt（）方法来查看茶壶。当我使用Frustum和Ortho方法时，对象会变形。

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import javax.media.opengl.*;
import javax.media.opengl.glu.*;
import javax.media.opengl.awt.*;
import com.sun.opengl.util.*;
import com.sun.opengl.util.gl2.*; // abet ama zyad bkayn bo 3D

class ThreeDTemp implements GLEventListener {
        JFrame frame;
        GLCanvas canvas;
        Animator animator;

        public ThreeDTemp(){
            frame = new JFrame("Open GL");
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

            canvas = new GLCanvas();
            canvas.setSize(1000, 600);
            canvas.addGLEventListener(this);

            frame.add(canvas);

            animator = new Animator(canvas);
            animator.start();

            frame.pack();
            frame.setVisible(true);
            frame.requestFocus();
        }

        public void init(GLAutoDrawable drawable) {

            GL2 gl = drawable.getGL().getGL2();
            GLU glu = new GLU();

            gl.glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
            gl.glMatrixMode(GL2.GL_PROJECTION);
            gl.glLoadIdentity();

            //gl.glOrtho(-500,500,-300,300,-300,300);
            gl.glFrustum(-1,1,-1,1,1.5,20);
            gl.glMatrixMode(GL2.GL_MODELVIEW);
            gl.glLoadIdentity();

            gl.glEnable(GL2.GL_DEPTH_TEST); // abet amash bnusen bo 3d

        }


        public void display(GLAutoDrawable drawable) {

            GL2 gl = drawable.getGL().getGL2();
            GLU glu = new GLU();
            GLUT glut= new GLUT();

            gl.glClear(GL.GL_COLOR_BUFFER_BIT | GL.GL_DEPTH_BUFFER_BIT);//abet aw depth a zyad bkayn
            gl.glColor3f(0f ,0.5f ,0.5f);
            gl.glLoadIdentity();
            glut.glutWireTeapot(200);

            //glu.gluLookAt(5,0,0,0,0,0,0,1,0);

            gl.glFlush();
        }

        public void reshape(GLAutoDrawable drawable, int x, int y, int width, int height) {   }

        public void dispose(GLAutoDrawable drawable) {}

        //Main Method
        public static void main(String[] args){
            new ThreeDTemp();
        }
}