JOGL GLU 使用抛出 GLException

Question

我正在尝试掌握 JOGL（和一般的 OGL），并从内存中生成了以下代码（除了 reshape() 回调），所以我不希望 OGL 是完美的。但是，我对 GLU 对象以及 gluLookAt() 和 gluPerspective() 方法的使用导致了一个我完全无法理解的神秘错误。

显然我可以去copy/paste教程中的一些工作代码，但我宁愿学习能够凭记忆工作，所以如果有人能向我解释我做错了什么，我将不胜感激。

import java.awt.Dimension;

import javax.media.opengl.GL;
import javax.media.opengl.GL2;
import javax.media.opengl.GLAutoDrawable;
import javax.media.opengl.GLEventListener;
import javax.media.opengl.awt.GLCanvas;
import javax.media.opengl.glu.GLU;
import javax.swing.*;

import com.jogamp.opengl.util.gl2.GLUT;

public class Sandbox extends GLCanvas implements GLEventListener
{
    GLU glu;

    public static void main(String[] args) 
    {
        GLCanvas canvas = new Sandbox();
        canvas.setPreferredSize(new Dimension(640, 480));
        JFrame frame = new JFrame("OGL");
        frame.getContentPane().add(canvas);

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

    public Sandbox()
    {
        this.addGLEventListener(this);
    }

    @Override
    public void init(GLAutoDrawable drawable) 
    {
        GL2 gl = drawable.getGL().getGL2();
        gl.glMatrixMode(GL2.GL_PROJECTION);
        gl.glClearColor(1.0f, 0.0f, 0.0f, 0.0f);
        glu.gluLookAt(0.0f, 2.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f);
    }

    @Override
    public void dispose(GLAutoDrawable drawable) 
    {
        // TODO Auto-generated method stub

    }

    @Override
    public void display(GLAutoDrawable drawable) 
    {
        GL2 gl = drawable.getGL().getGL2();
        gl.glClear(GL.GL_COLOR_BUFFER_BIT);

        gl.glLoadIdentity();

        GLUT glut = new GLUT();
        glut.glutSolidSphere(3.0f, 50, 50);
    }

    @Override
    public void reshape(GLAutoDrawable drawable, int x, int y, int width, int height) 
    {
         GL2 gl = drawable.getGL().getGL2();  // get the OpenGL 2 graphics context

          if (height == 0) height = 1;   // prevent divide by zero
          float aspect = (float)width / height;

          // Set the view port (display area) to cover the entire window
          gl.glViewport(0, 0, width, height);

          // Setup perspective projection, with aspect ratio matches viewport
          gl.glMatrixMode(GL2.GL_PROJECTION);  // choose projection matrix
          gl.glLoadIdentity();             // reset projection matrix
          glu.gluPerspective(45.0, aspect, 0.1, 100.0); // fovy, aspect, zNear, zFar

          // Enable the model-view transform
          gl.glMatrixMode(GL2.GL_MODELVIEW);
          gl.glLoadIdentity(); // reset

    }
}

和错误：（gluLookAt() 和 gluPerspective() 都会产生这个错误）

Exception in thread "AWT-EventQueue-0" javax.media.opengl.GLException: Caught NullPointerException: null on thread AWT-EventQueue-0
    at javax.media.opengl.GLException.newGLException(GLException.java:75)
    at jogamp.opengl.GLDrawableHelper.invokeGLImpl(GLDrawableHelper.java:1311)
    at jogamp.opengl.GLDrawableHelper.invokeGL(GLDrawableHelper.java:1131)
    at javax.media.opengl.awt.GLCanvas.run(GLCanvas.java:1394)
    at javax.media.opengl.Threading.invoke(Threading.java:223)
    at javax.media.opengl.awt.GLCanvas.display(GLCanvas.java:525)
    at javax.media.opengl.awt.GLCanvas.paint(GLCanvas.java:579)
    at sun.awt.RepaintArea.paintComponent(Unknown Source)
    at sun.awt.RepaintArea.paint(Unknown Source)
    at sun.awt.windows.WComponentPeer.handleEvent(Unknown Source)
    at java.awt.Component.dispatchEventImpl(Unknown Source)
    at java.awt.Component.dispatchEvent(Unknown Source)
    at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
    at java.awt.EventQueue.access0(Unknown Source)
    at java.awt.EventQueue.run(Unknown Source)
    at java.awt.EventQueue.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain.doIntersectionPrivilege(Unknown Source)
    at java.security.ProtectionDomain.doIntersectionPrivilege(Unknown Source)
    at java.awt.EventQueue.run(Unknown Source)
    at java.awt.EventQueue.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain.doIntersectionPrivilege(Unknown Source)
    at java.awt.EventQueue.dispatchEvent(Unknown Source)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.run(Unknown Source)
Caused by: java.lang.NullPointerException
    at Sandbox.init(Sandbox.java:39)
    at jogamp.opengl.GLDrawableHelper.init(GLDrawableHelper.java:640)
    at jogamp.opengl.GLDrawableHelper.init(GLDrawableHelper.java:662)
    at javax.media.opengl.awt.GLCanvas.run(GLCanvas.java:1366)
    at jogamp.opengl.GLDrawableHelper.invokeGLImpl(GLDrawableHelper.java:1275)
    ... 28 more

Answer 1

您永远不会创建一个对象并将其分配给您的全局对象 glu。

Exception in thread "AWT-EventQueue-0" javax.media.opengl.GLException: Caught NullPointerException: null on thread AWT-EventQueue-0

GLException 表示它已捕获到 NullPointerException。这基本上意味着执行 "empty" 对象的任何方法都会抛出这样的异常。

尝试在初始化方法中添加以下内容：

glu = new GLU();

JOGL GLU 使用抛出 GLException

JOGL GLU usage throwing GLException

java

opengl

jogl