Posted by Remco47 on Jun 14, 2011; 2:38pm
URL: https://forum.jogamp.org/OpenGL-4-Tessellation-Doesn-t-Work-tp3063244.html

Hi, I have a problem with OpenGL 4 tessellation. I draw 4 vertices in GL_PATCHES mode, with GL_PATCH_VERTICES set to 4 and all the default levels set to 64. I expect OpenGL to recognize the vertices as a quad, and subdivide it into 64 by 64 quads. For some reason, all that appears on screen is 4 points. Below is a small test case:

import java.awt.*;
import java.awt.event.*;
import javax.media.opengl.*;
import javax.media.opengl.awt.*;

public class TessellatorTest implements GLEventListener {
    public TessellatorTest()
    {
        GLProfile profile = GLProfile.get(GLProfile.GL4bc);
        GLCapabilities caps = new GLCapabilities(profile);
        GLCanvas canvas = new GLCanvas(caps);
        canvas.addGLEventListener(this);
       
        Frame frame = new Frame("Hello world!");
        frame.add(canvas);
        frame.addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent e) { System.exit(0); }
        });
        frame.setSize(500, 500);
        frame.setResizable(false);
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        new TessellatorTest();
    }

    public void display(GLAutoDrawable drawable) {
        GL4bc gl = drawable.getGL().getGL4bc();

        gl.glPolygonMode(GL4bc.GL_FRONT, GL4bc.GL_LINE);
        gl.glPatchParameteri(GL4bc.GL_PATCH_VERTICES, 4);
        gl.glPatchParameterfv(GL4bc.GL_PATCH_DEFAULT_OUTER_LEVEL, new float[]{ 64, 64, 64, 64 }, 0);
        gl.glPatchParameterfv(GL4bc.GL_PATCH_DEFAULT_INNER_LEVEL, new float[]{ 64, 64 }, 0);
        gl.glBegin(GL4bc.GL_PATCHES);
        gl.glVertex3f(-0.8f, -0.8f, 0);
        gl.glVertex3f( 0.8f, -0.8f, 0);
        gl.glVertex3f( 0.8f,  0.8f, 0);
        gl.glVertex3f(-0.8f,  0.8f, 0);
        gl.glEnd();
    }

    public void init(GLAutoDrawable a){}
    public void reshape(GLAutoDrawable a, int b, int c, int d, int e){}
    public void dispose(GLAutoDrawable a){}
}