JOGLでフォグをつけてレンダリングする

JOGLでフォグをつけてレンダリングするには、以下のコードを実行します。

import java.io.*;
import javax.media.opengl.*;
import com.sun.opengl.util.*;

public class JoglSample36
{
    // 出力画像サイズ
    private static int width = 300;
    private static int height = 300;

    public static void main(String args[])
        throws IOException
    {
        GLDrawableFactory gldf = 
            GLDrawableFactory.getFactory();
        GLCapabilities glc = new GLCapabilities();
        glc.setDoubleBuffered(false);
        GLPbuffer buf = gldf.createGLPbuffer(
           glc, null, width, height, null);

        buf.addGLEventListener(
            new GLEventListener(){
            // 初期化
            public void init(GLAutoDrawable dr)
            {
                GL gl = dr.getGL();
                // 背景色
                gl.glClearColor(
                    (float)0x88/(float)0xff, 
                    (float)0x88/(float)0xff, 
                    (float)0x88/(float)0xff,
                    1f);
            }

            public void display(GLAutoDrawable dr)
            {
                GL gl = dr.getGL();
                GLUT glut = new GLUT();
                gl.glViewport(0, 0, width, height);

                // 透視投影
                gl.glMatrixMode(GL.GL_PROJECTION);
                gl.glLoadIdentity();
                float ratio = (float)height/(float)width;
                gl.glFrustum(-1.0f, 1.0f, -ratio, ratio,
                    5.0f, 40.0f);

                gl.glMatrixMode(GL.GL_MODELVIEW);
                gl.glLoadIdentity();
                gl.glTranslatef(-3.0f, -1.5f, -7.0f);

                gl.glEnable(GL.GL_LIGHTING);
                gl.glEnable(GL.GL_LIGHT0);
                gl.glEnable(gl.GL_COLOR_MATERIAL);
                gl.glEnable(GL.GL_NORMALIZE);
                gl.glEnable(GL.GL_DEPTH_TEST);
//                gl.glEnable(GL.GL_CULL_FACE);

                float fog[]={1.0f,1.0f,1.0f,1.0f};
                gl.glFogfv(GL.GL_FOG_COLOR,fog,0);
                gl.glFogi(GL.GL_FOG_MODE,GL.GL_EXP);
                gl.glFogf(GL.GL_FOG_DENSITY, 0.08f);
                gl.glFogf(GL.GL_FOG_START, 0.0f);
                gl.glFogf(GL.GL_FOG_END,10.0f);
                gl.glEnable(GL.GL_FOG);

                gl.glClear(GL.GL_COLOR_BUFFER_BIT |
                    GL.GL_DEPTH_BUFFER_BIT );

                gl.glPushMatrix();
                // X軸回転
                gl.glRotatef(15.0f, 1.0f, 0.0f, 0.0f);
                // Y軸回転
                gl.glRotatef(30.0f, 0.0f, 1.0f, 0.0f);

                float cs = 0.3f;
                float gs = 0.6f;
                int xs = 30;
                int zs = 30;
                for(int lz=0;lz<zs;lz++){
                    for(int lx=0;lx<xs;lx++){
                        if( (lx+lz)%2 == 0 ){
                            gl.glColor3f(
                              (float)0xff/(float)0xff, 
                              (float)0xff/(float)0xff, 
                              (float)0xff/(float)0xff
                            );
                        } else {
                            gl.glColor3f(
                              (float)0x77/(float)0xff, 
                              (float)0x99/(float)0xff, 
                              (float)0xff/(float)0xff
                            );
                        }
                        gl.glPushMatrix();
                        gl.glTranslatef(lx*gs, 0.0f, -1*lz*gs);
                        glut.glutSolidCube(cs);
                        gl.glPopMatrix();
                    }
                }

                gl.glPopMatrix();
            }

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

            public void displayChanged(
                GLAutoDrawable dr,
                boolean modeChanged,
                boolean deviceChanged){}
          }
        );

        GLContext context =  buf.createContext(null);
        context.makeCurrent();
        buf.display();
        Screenshot.writeToFile(
            new File("sample1194a.png"), width, height, true);
        context.release();
        context.destroy();
    }
}

出力画像(sample1194a.png)