JOGL white texture?

问题:

I am trying to load earth.png and place it over a triangle. The image is 256x256. I have followed an online tutorial and played around with this for hours, but the triangle still remains white. Can any one point me in the right direction.

import java.awt.Frame;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.io.IOException;
import java.io.InputStream;

import javax.media.opengl.*;
import javax.media.opengl.awt.GLCanvas;

import com.jogamp.opengl.util.texture.Texture;
import com.jogamp.opengl.util.texture.TextureData;
import com.jogamp.opengl.util.texture.TextureIO;

public class test implements GLEventListener {
    private Texture earthTexture;

    public static void main(String[] args) {
        GLProfile glp = GLProfile.getDefault();
        GLCapabilities caps = new GLCapabilities(glp);
        GLCanvas canvas = new GLCanvas(caps);

        final Frame frame = new Frame("AWT Window Test111");
        frame.setSize(700, 700);
        frame.add(canvas);
        frame.setVisible(true);

        // by default, an AWT Frame doesn't do anything when you click
        // the close button; this bit of code will terminate the program when
        // the window is asked to close
        frame.addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent e) {
                frame.dispose();
                System.exit(0);
            }
        });
    canvas.addGLEventListener(new test());

    }


    @Override
    public void display(GLAutoDrawable arg0) {


        update();
        render(arg0);


    }

    private void update() {
        // TODO Auto-generated method stub

    }

    private void render(GLAutoDrawable drawable) {

        GL2 gl = drawable.getGL().getGL2();
        gl.glClear(GL.GL_COLOR_BUFFER_BIT);
        gl.glEnable(GL.GL_TEXTURE_2D);

        gl.glBegin(GL2.GL_TRIANGLES);                           // Begin drawing triangle sides

        earthTexture.enable();
        earthTexture.bind();

        // gl.glColor3f( 1.0f, 0.0f, 0.0f);                     // Set colour to red
    gl.glTexCoord2f(0.0f, 0.0f);
    gl.glVertex3f( 0.0f, 1.0f, 1.0f);                       // Top vertex
    gl.glTexCoord2f(-1.0f, -2.0f);
    gl.glVertex3f(-1.0f,-1.0f, 0.0f);                       // Bottom left vertex
    gl.glTexCoord2f(1.0f, -2.0f);
    gl.glVertex3f( 1.0f,-1.0f, 0.0f);                       // Bottom right vertex

        gl.glEnd();

    }

    @Override
    public void dispose(GLAutoDrawable arg0) {
        // TODO Auto-generated method stub

    }

    @Override
    public void init(GLAutoDrawable arg0) {
        GL2 gl = arg0.getGL().getGL2();

        // Load texture.
       try {
            InputStream stream = getClass().getResourceAsStream("earth.png");
           TextureData data = TextureIO.newTextureData(gl.getGLProfile(), stream, 100, 200, false, "png");
           earthTexture = TextureIO.newTexture(data);
       }
       catch (IOException exc) {
           exc.printStackTrace();
           System.exit(1);
       }


    }

    @Override
    public void reshape(GLAutoDrawable arg0, int arg1, int arg2, int arg3,
            int arg4) {
        // TODO Auto-generated method stub

    }



}

回答1:

A couple of things I have noticed:

You need to explicitly enable texturing within OpenGL, by using something like:

gl.glEnable(GL.GL_TEXTURE_2D);

You also will need to specify coordinates for the textures (typically expressed as u,v coordinates), this needs to be done for every 3D point:

gl.glTexCoord2f(0.0f, 0.0f);
gl.glVertex3f( 0.0f, 1.0f, 1.0f); 
...

The excellent NeHe tutorials also have JOGL sample code these days, which will be worthwhile looking at in more depth:

http://nehe.gamedev.net/data/lessons/lesson.asp?lesson=07

This article also has some good information on understanding texture coordiantes:

http://www.opengl.org/resources/code/samples/sig99/advanced99/notes/node52.html

回答2:

You are binding your texture in between the glBegin/glEnd statements. It is required to do so before the glBegin. Texture switches in between begin/end pairs are likely to be ignored.