Vertex Arrays Example Program

import javax.media.opengl.*;
import javax.media.opengl.glu.*;
import com.sun.opengl.util.*; // GLUT, FPSAnimator
import java.nio.FloatBuffer;

import java.util.Random;

class VertexArray {

  //////////////// Constants /////////////////////////

  // Number of Points in the array.
  final int nbPoints = 20000;

  //////////////// Variables /////////////////////////

  // We use a buffer and an array for the vertex data
  // to more compatible with C.
  FloatBuffer points;
  float[] pointsData;
  FloatBuffer colors;
  float[] colorsData;
  
  Random random = new Random();

  ///////////////// Functions /////////////////////////

  public void init ( GL gl )
    {
      gl.glEnableClientState( GL.GL_VERTEX_ARRAY );
      gl.glEnableClientState( GL.GL_COLOR_ARRAY );
      //gl.glEnableClientState( GL.GL_NORMAL_ARRAY );

      initArrayData( gl );
    }
  
  ///////////////// create data ///////////////////////


  private void initArrayData( GL gl )
    {
      // Create data points on the surface of a cube.
      int nbValues = nbPoints * 3;
      pointsData = new float[ nbValues ];
      colorsData = new float[ nbValues ];
      for( int i=0; i < nbPoints; i++ )
      {
	pointsData[ i ] = (float)Math.random();
	pointsData[ i+1 ] = (float)Math.random();
	pointsData[ i+2 ] = (float)Math.random();
	// Cast on random side surface.
	int sel = random.nextInt( 3 );
	pointsData [ i + sel ] = random.nextInt( 2 );
	//
	colorsData[ i ] = (float)Math.random();
	colorsData[ i+1 ] = (float)Math.random();
	colorsData[ i+2 ] = (float)Math.random();
	colorsData [ i + sel ] = 1f;
      }
      // Points.
      points = BufferUtil.newFloatBuffer( nbValues );
      points.put( pointsData, 0, nbValues );
      points.rewind();
      gl.glVertexPointer( 3, GL.GL_FLOAT, 0, points );
      // Colors.
      colors = BufferUtil.newFloatBuffer( nbValues );
      colors.put( colorsData, 0, nbValues );
      colors.rewind();
      gl.glColorPointer( 3, GL.GL_FLOAT, 0, colors );
    }

  //////////////////////// draw /////////////////////////

  public void draw( GL gl )
    {
      gl.glColor3f( 0f, 1f, 0f ); 
//       gl.glBegin( GL.GL_POINTS ); {
// 	for( int i=0; i < nbPoints; i++ ) 
// 	{
// 	  gl.glVertex3fv( pointsData, i*3 );
// // 	  gl.glVertex3f( points.get( i*3 ),
// // 			 points.get( i*3 +1),
// // 			 points.get( i*3 +2) );

// 	  //gl.glArrayElement( i );
// 	}      
//       } gl.glEnd();
      gl.glColor3f( 1f, 0f, 0f ); 
      gl.glDrawArrays( GL.GL_POINTS, 0, nbPoints );
    }

}