Posted by s3a on Jul 28, 2011; 6:24pm
URL: https://forum.jogamp.org/Can-someone-please-help-me-complete-this-sample-code-tp3207414.html

I am reading C++ OpenGL tutorials on random websites and this is the translation I made. I am using JOGL 1.1.1/OpenGL 2.1 (and I am avoiding deprecated code).

My current problem is understanding what these two lines do (or if I translated them correctly from C++ since my Java is good but my C++ isn't so great - I am working on my C++ skills separately):

gl.glGenBuffers(1, &positionBufferObject);
gl.glBindBuffer(GL.GL_ARRAY_BUFFER, positionBufferObject);

If I did anything else wrong, please correct me for that too. I'm still trying to make a polygon or some kind of shape display in 3D without using syntax like glBegin and glEnd as a "Hello world" type of program so that I can get started for real. Basically, I think I am avoiding the fixed function pipeline and aiming at using the programmable shader pipeline.

Here is the mini-JOGL code sample I made:

import javax.media.opengl.GL;
import javax.media.opengl.GLAutoDrawable;
import javax.media.opengl.GLCanvas;
import javax.media.opengl.GLEventListener;
import javax.swing.JFrame;

public class Third implements GLEventListener
{
    public void init(GLAutoDrawable glad) {

    }

    public void display(GLAutoDrawable drawable) {
        // What I know works
        GL gl = drawable.getGL();
        gl.glClearColor(0.1f, 0.5f, 1.0f, 0.7f);
        gl.glClear(GL.GL_COLOR_BUFFER_BIT);
        gl.glFlush();

        // What I'm trying to learn now
        int theProgram = gl.glCreateProgram();
        gl.glUseProgram(theProgram);

        gl.glGenBuffers(1, &positionBufferObject); // This seems pointer-ish (I do not know much about C++ pointers yet) - is it incorrect in Java use?
        gl.glBindBuffer(GL.GL_ARRAY_BUFFER, positionBufferObject); // I am trying to create a positionBufferObject object reference variable on the line above
        gl.glEnableVertexAttribArray(0);
        gl.glVertexAttribPointer(0, 4, GL.GL_FLOAT, false, 0, 0);

        gl.glDrawArrays(GL.GL_TRIANGLES, 0, 3);

        gl.glDisableVertexAttribArray(0);
        gl.glUseProgram(0);

//        gl.glutSwapBuffers();
    }

    public void reshape(GLAutoDrawable glad, int i, int i1, int i2, int i3) {

    }

    public void displayChanged(GLAutoDrawable glad, boolean bln, boolean bln1) {

    }

    public static void main(String[] args) {
        JFrame frame = new JFrame("TheFrame");
        GLCanvas canvas = new GLCanvas();
        canvas.addGLEventListener(new Third());
        frame.add(canvas);
        frame.setSize(300,300);
        frame.setVisible(true);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
}

Any input would be greatly appreciated!
Thanks in advance!